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diff --git a/external-libs/pcre/doc/Tech.Notes b/external-libs/pcre/doc/Tech.Notes new file mode 100644 index 00000000..73c31c7c --- /dev/null +++ b/external-libs/pcre/doc/Tech.Notes @@ -0,0 +1,281 @@ +Technical Notes about PCRE +-------------------------- + +Many years ago I implemented some regular expression functions to an algorithm +suggested by Martin Richards. These were not Unix-like in form, and were quite +restricted in what they could do by comparison with Perl. The interesting part +about the algorithm was that the amount of space required to hold the compiled +form of an expression was known in advance. The code to apply an expression did +not operate by backtracking, as the original Henry Spencer code and current +Perl code does, but instead checked all possibilities simultaneously by keeping +a list of current states and checking all of them as it advanced through the +subject string. (In the terminology of Jeffrey Friedl's book, it was a "DFA +algorithm".) When the pattern was all used up, all remaining states were +possible matches, and the one matching the longest subset of the subject string +was chosen. This did not necessarily maximize the individual wild portions of +the pattern, as is expected in Unix and Perl-style regular expressions. + +By contrast, the code originally written by Henry Spencer and subsequently +heavily modified for Perl actually compiles the expression twice: once in a +dummy mode in order to find out how much store will be needed, and then for +real. The execution function operates by backtracking and maximizing (or, +optionally, minimizing in Perl) the amount of the subject that matches +individual wild portions of the pattern. This is an "NFA algorithm" in Friedl's +terminology. + +For the set of functions that forms PCRE (which are unrelated to those +mentioned above), I tried at first to invent an algorithm that used an amount +of store bounded by a multiple of the number of characters in the pattern, to +save on compiling time. However, because of the greater complexity in Perl +regular expressions, I couldn't do this. In any case, a first pass through the +pattern is needed, for a number of reasons. PCRE works by running a very +degenerate first pass to calculate a maximum store size, and then a second pass +to do the real compile - which may use a bit less than the predicted amount of +store. The idea is that this is going to turn out faster because the first pass +is degenerate and the second pass can just store stuff straight into the +vector. It does make the compiling functions bigger, of course, but they have +got quite big anyway to handle all the Perl stuff. + +The compiled form of a pattern is a vector of bytes, containing items of +variable length. The first byte in an item is an opcode, and the length of the +item is either implicit in the opcode or contained in the data bytes which +follow it. A list of all the opcodes follows: + +Opcodes with no following data +------------------------------ + +These items are all just one byte long + + OP_END end of pattern + OP_ANY match any character + OP_ANYBYTE match any single byte, even in UTF-8 mode + OP_SOD match start of data: \A + OP_SOM, start of match (subject + offset): \G + OP_CIRC ^ (start of data, or after \n in multiline) + OP_NOT_WORD_BOUNDARY \W + OP_WORD_BOUNDARY \w + OP_NOT_DIGIT \D + OP_DIGIT \d + OP_NOT_WHITESPACE \S + OP_WHITESPACE \s + OP_NOT_WORDCHAR \W + OP_WORDCHAR \w + OP_EODN match end of data or \n at end: \Z + OP_EOD match end of data: \z + OP_DOLL $ (end of data, or before \n in multiline) + + +Repeating single characters +--------------------------- + +The common repeats (*, +, ?) when applied to a single character appear as +two-byte items using the following opcodes: + + OP_STAR + OP_MINSTAR + OP_PLUS + OP_MINPLUS + OP_QUERY + OP_MINQUERY + +Those with "MIN" in their name are the minimizing versions. Each is followed by +the character that is to be repeated. Other repeats make use of + + OP_UPTO + OP_MINUPTO + OP_EXACT + +which are followed by a two-byte count (most significant first) and the +repeated character. OP_UPTO matches from 0 to the given number. A repeat with a +non-zero minimum and a fixed maximum is coded as an OP_EXACT followed by an +OP_UPTO (or OP_MINUPTO). + + +Repeating character types +------------------------- + +Repeats of things like \d are done exactly as for single characters, except +that instead of a character, the opcode for the type is stored in the data +byte. The opcodes are: + + OP_TYPESTAR + OP_TYPEMINSTAR + OP_TYPEPLUS + OP_TYPEMINPLUS + OP_TYPEQUERY + OP_TYPEMINQUERY + OP_TYPEUPTO + OP_TYPEMINUPTO + OP_TYPEEXACT + + +Matching a character string +--------------------------- + +The OP_CHARS opcode is followed by a one-byte count and then that number of +characters. If there are more than 255 characters in sequence, successive +instances of OP_CHARS are used. + + +Character classes +----------------- + +If there is only one character, OP_CHARS is used for a positive class, +and OP_NOT for a negative one (that is, for something like [^a]). However, in +UTF-8 mode, this applies only to characters with values < 128, because OP_NOT +is confined to single bytes. + +Another set of repeating opcodes (OP_NOTSTAR etc.) are used for a repeated, +negated, single-character class. The normal ones (OP_STAR etc.) are used for a +repeated positive single-character class. + +When there's more than one character in a class and all the characters are less +than 256, OP_CLASS is used for a positive class, and OP_NCLASS for a negative +one. In either case, the opcode is followed by a 32-byte bit map containing a 1 +bit for every character that is acceptable. The bits are counted from the least +significant end of each byte. + +The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8 mode, +subject characters with values greater than 256 can be handled correctly. For +OP_CLASS they don't match, whereas for OP_NCLASS they do. + +For classes containing characters with values > 255, OP_XCLASS is used. It +optionally uses a bit map (if any characters lie within it), followed by a list +of pairs and single characters. There is a flag character than indicates +whether it's a positive or a negative class. + + +Back references +--------------- + +OP_REF is followed by two bytes containing the reference number. + + +Repeating character classes and back references +----------------------------------------------- + +Single-character classes are handled specially (see above). This applies to +OP_CLASS and OP_REF. In both cases, the repeat information follows the base +item. The matching code looks at the following opcode to see if it is one of + + OP_CRSTAR + OP_CRMINSTAR + OP_CRPLUS + OP_CRMINPLUS + OP_CRQUERY + OP_CRMINQUERY + OP_CRRANGE + OP_CRMINRANGE + +All but the last two are just single-byte items. The others are followed by +four bytes of data, comprising the minimum and maximum repeat counts. + + +Brackets and alternation +------------------------ + +A pair of non-capturing (round) brackets is wrapped round each expression at +compile time, so alternation always happens in the context of brackets. + +Non-capturing brackets use the opcode OP_BRA, while capturing brackets use +OP_BRA+1, OP_BRA+2, etc. [Note for North Americans: "bracket" to some English +speakers, including myself, can be round, square, curly, or pointy. Hence this +usage.] + +Originally PCRE was limited to 99 capturing brackets (so as not to use up all +the opcodes). From release 3.5, there is no limit. What happens is that the +first ones, up to EXTRACT_BASIC_MAX are handled with separate opcodes, as +above. If there are more, the opcode is set to EXTRACT_BASIC_MAX+1, and the +first operation in the bracket is OP_BRANUMBER, followed by a 2-byte bracket +number. This opcode is ignored while matching, but is fished out when handling +the bracket itself. (They could have all been done like this, but I was making +minimal changes.) + +A bracket opcode is followed by two bytes which give the offset to the next +alternative OP_ALT or, if there aren't any branches, to the matching KET +opcode. Each OP_ALT is followed by two bytes giving the offset to the next one, +or to the KET opcode. + +OP_KET is used for subpatterns that do not repeat indefinitely, while +OP_KETRMIN and OP_KETRMAX are used for indefinite repetitions, minimally or +maximally respectively. All three are followed by two bytes giving (as a +positive number) the offset back to the matching BRA opcode. + +If a subpattern is quantified such that it is permitted to match zero times, it +is preceded by one of OP_BRAZERO or OP_BRAMINZERO. These are single-byte +opcodes which tell the matcher that skipping this subpattern entirely is a +valid branch. + +A subpattern with an indefinite maximum repetition is replicated in the +compiled data its minimum number of times (or once with a BRAZERO if the +minimum is zero), with the final copy terminating with a KETRMIN or KETRMAX as +appropriate. + +A subpattern with a bounded maximum repetition is replicated in a nested +fashion up to the maximum number of times, with BRAZERO or BRAMINZERO before +each replication after the minimum, so that, for example, (abc){2,5} is +compiled as (abc)(abc)((abc)((abc)(abc)?)?)?. The 99 and 200 bracket limits do +not apply to these internally generated brackets. + + +Assertions +---------- + +Forward assertions are just like other subpatterns, but starting with one of +the opcodes OP_ASSERT or OP_ASSERT_NOT. Backward assertions use the opcodes +OP_ASSERTBACK and OP_ASSERTBACK_NOT, and the first opcode inside the assertion +is OP_REVERSE, followed by a two byte count of the number of characters to move +back the pointer in the subject string. When operating in UTF-8 mode, the count +is a character count rather than a byte count. A separate count is present in +each alternative of a lookbehind assertion, allowing them to have different +fixed lengths. + + +Once-only subpatterns +--------------------- + +These are also just like other subpatterns, but they start with the opcode +OP_ONCE. + + +Conditional subpatterns +----------------------- + +These are like other subpatterns, but they start with the opcode OP_COND. If +the condition is a back reference, this is stored at the start of the +subpattern using the opcode OP_CREF followed by two bytes containing the +reference number. If the condition is "in recursion" (coded as "(?(R)"), the +same scheme is used, with a "reference number" of 0xffff. Otherwise, a +conditional subpattern always starts with one of the assertions. + + +Recursion +--------- + +Recursion either matches the current regex, or some subexpression. The opcode +OP_RECURSE is followed by an value which is the offset to the starting bracket +from the start of the whole pattern. + + +Callout +------- + +OP_CALLOUT is followed by one byte of data that holds a callout number in the +range 0 to 255. + + +Changing options +---------------- + +If any of the /i, /m, or /s options are changed within a pattern, an OP_OPT +opcode is compiled, followed by one byte containing the new settings of these +flags. If there are several alternatives, there is an occurrence of OP_OPT at +the start of all those following the first options change, to set appropriate +options for the start of the alternative. Immediately after the end of the +group there is another such item to reset the flags to their previous values. A +change of flag right at the very start of the pattern can be handled entirely +at compile time, and so does not cause anything to be put into the compiled +data. + +Philip Hazel +August 2003 diff --git a/external-libs/pcre/doc/html/index.html b/external-libs/pcre/doc/html/index.html new file mode 100644 index 00000000..3751ff0f --- /dev/null +++ b/external-libs/pcre/doc/html/index.html @@ -0,0 +1,102 @@ +<html> +<head> +<title>PCRE specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>Perl-compatible Regular Expressions (PCRE)</h1> +<p> +The HTML documentation for PCRE comprises the following pages: +</p> + +<table> +<tr><td><a href="pcre.html">pcre</a></td> + <td> Introductory page</td></tr> + +<tr><td><a href="pcreapi.html">pcreapi</a></td> + <td> PCRE's native API</td></tr> + +<tr><td><a href="pcrebuild.html">pcrebuild</a></td> + <td> Options for building PCRE</td></tr> + +<tr><td><a href="pcrecallout.html">pcrecallout</a></td> + <td> The <i>callout</i> facility</td></tr> + +<tr><td><a href="pcrecompat.html">pcrecompat</a></td> + <td> Compability with Perl</td></tr> + +<tr><td><a href="pcregrep.html">pcregrep</a></td> + <td> The <b>pcregrep</b> command</td></tr> + +<tr><td><a href="pcrepattern.html">pcrepattern</a></td> + <td> Regular expressions supported by PCRE</td></tr> + +<tr><td><a href="pcreperform.html">pcreperform</a></td> + <td> Some comments on performance</td></tr> + +<tr><td><a href="pcreposix.html">pcreposix</a></td> + <td> The POSIX API to the PCRE library</td></tr> + +<tr><td><a href="pcresample.html">pcresample</a></td> + <td> Description of the sample program</td></tr> + +<tr><td><a href="pcretest.html">pcretest</a></td> + <td> The <b>pcretest</b> command for testing PCRE</td></tr> +</table> + +<p> +There are also individual pages that summarize the interface for each function +in the library: +</p> + +<table> + +<tr><td><a href="pcre_compile.html">pcre_compile</a></td> + <td> Compile a regular expression</td></tr> + +<tr><td><a href="pcre_config.html">pcre_config</a></td> + <td> Show build-time configuration options</td></tr> + +<tr><td><a href="pcre_copy_named_substring.html">pcre_copy_named_substring</a></td> + <td> Extract named substring into given buffer</td></tr> + +<tr><td><a href="pcre_copy_substring.html">pcre_copy_substring</a></td> + <td> Extract numbered substring into given buffer</td></tr> + +<tr><td><a href="pcre_exec.html">pcre_exec</a></td> + <td> Match a compiled pattern to a subject string</td></tr> + +<tr><td><a href="pcre_free_substring.html">pcre_free_substring</a></td> + <td> Free extracted substring</td></tr> + +<tr><td><a href="pcre_free_substring_list.html">pcre_free_substring_list</a></td> + <td> Free list of extracted substrings</td></tr> + +<tr><td><a href="pcre_fullinfo.html">pcre_fullinfo</a></td> + <td> Extract information about a pattern</td></tr> + +<tr><td><a href="pcre_get_named_substring.html">pcre_get_named_substring</a></td> + <td> Extract named substring into new memory</td></tr> + +<tr><td><a href="pcre_get_stringnumber.html">pcre_get_stringnumber</a></td> + <td> Convert captured string name to number</td></tr> + +<tr><td><a href="pcre_get_substring.html">pcre_get_substring</a></td> + <td> Extract numbered substring into new memory</td></tr> + +<tr><td><a href="pcre_get_substring_list.html">pcre_get_substring_list</a></td> + <td> Extract all substrings into new memory</td></tr> + +<tr><td><a href="pcre_info.html">pcre_info</a></td> + <td> Obsolete information extraction function</td></tr> + +<tr><td><a href="pcre_maketables.html">pcre_maketables</a></td> + <td> Build character tables in current locale</td></tr> + +<tr><td><a href="pcre_study.html">pcre_study</a></td> + <td> Study a compiled pattern</td></tr> + +<tr><td><a href="pcre_version.html">pcre_version</a></td> + <td> Return PCRE version and release date</td></tr> +</table> + +</html> diff --git a/external-libs/pcre/doc/html/pcre.html b/external-libs/pcre/doc/html/pcre.html new file mode 100644 index 00000000..bb0d3548 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre.html @@ -0,0 +1,190 @@ +<html> +<head> +<title>pcre specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">DESCRIPTION</a> +<li><a name="TOC2" href="#SEC2">USER DOCUMENTATION</a> +<li><a name="TOC3" href="#SEC3">LIMITATIONS</a> +<li><a name="TOC4" href="#SEC4">UTF-8 SUPPORT</a> +<li><a name="TOC5" href="#SEC5">AUTHOR</a> +</ul> +<br><a name="SEC1" href="#TOC1">DESCRIPTION</a><br> +<P> +The PCRE library is a set of functions that implement regular expression +pattern matching using the same syntax and semantics as Perl, with just a few +differences. The current implementation of PCRE (release 4.x) corresponds +approximately with Perl 5.8, including support for UTF-8 encoded strings. +However, this support has to be explicitly enabled; it is not the default. +</P> +<P> +PCRE is written in C and released as a C library. However, a number of people +have written wrappers and interfaces of various kinds. A C++ class is included +in these contributions, which can be found in the <i>Contrib</i> directory at +the primary FTP site, which is: +</P> +<a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre">ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre</a> +<P> +Details of exactly which Perl regular expression features are and are not +supported by PCRE are given in separate documents. See the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +and +<a href="pcrecompat.html"><b>pcrecompat</b></a> +pages. +</P> +<P> +Some features of PCRE can be included, excluded, or changed when the library is +built. The +<a href="pcre_config.html"><b>pcre_config()</b></a> +function makes it possible for a client to discover which features are +available. Documentation about building PCRE for various operating systems can +be found in the <b>README</b> file in the source distribution. +</P> +<br><a name="SEC2" href="#TOC1">USER DOCUMENTATION</a><br> +<P> +The user documentation for PCRE has been split up into a number of different +sections. In the "man" format, each of these is a separate "man page". In the +HTML format, each is a separate page, linked from the index page. In the plain +text format, all the sections are concatenated, for ease of searching. The +sections are as follows: +</P> +<P> +<pre> + pcre this document + pcreapi details of PCRE's native API + pcrebuild options for building PCRE + pcrecallout details of the callout feature + pcrecompat discussion of Perl compatibility + pcregrep description of the <b>pcregrep</b> command + pcrepattern syntax and semantics of supported + regular expressions + pcreperform discussion of performance issues + pcreposix the POSIX-compatible API + pcresample discussion of the sample program + pcretest the <b>pcretest</b> testing command +</PRE> +</P> +<P> +In addition, in the "man" and HTML formats, there is a short page for each +library function, listing its arguments and results. +</P> +<br><a name="SEC3" href="#TOC1">LIMITATIONS</a><br> +<P> +There are some size limitations in PCRE but it is hoped that they will never in +practice be relevant. +</P> +<P> +The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE is +compiled with the default internal linkage size of 2. If you want to process +regular expressions that are truly enormous, you can compile PCRE with an +internal linkage size of 3 or 4 (see the <b>README</b> file in the source +distribution and the +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation for details). If these cases the limit is substantially larger. +However, the speed of execution will be slower. +</P> +<P> +All values in repeating quantifiers must be less than 65536. +The maximum number of capturing subpatterns is 65535. +</P> +<P> +There is no limit to the number of non-capturing subpatterns, but the maximum +depth of nesting of all kinds of parenthesized subpattern, including capturing +subpatterns, assertions, and other types of subpattern, is 200. +</P> +<P> +The maximum length of a subject string is the largest positive number that an +integer variable can hold. However, PCRE uses recursion to handle subpatterns +and indefinite repetition. This means that the available stack space may limit +the size of a subject string that can be processed by certain patterns. +</P> +<a name="utf8support"></a><br><a name="SEC4" href="#TOC1">UTF-8 SUPPORT</a><br> +<P> +Starting at release 3.3, PCRE has had some support for character strings +encoded in the UTF-8 format. For release 4.0 this has been greatly extended to +cover most common requirements. +</P> +<P> +In order process UTF-8 strings, you must build PCRE to include UTF-8 support in +the code, and, in addition, you must call +<a href="pcre_compile.html"><b>pcre_compile()</b></a> +with the PCRE_UTF8 option flag. When you do this, both the pattern and any +subject strings that are matched against it are treated as UTF-8 strings +instead of just strings of bytes. +</P> +<P> +If you compile PCRE with UTF-8 support, but do not use it at run time, the +library will be a bit bigger, but the additional run time overhead is limited +to testing the PCRE_UTF8 flag in several places, so should not be very large. +</P> +<P> +The following comments apply when PCRE is running in UTF-8 mode: +</P> +<P> +1. When you set the PCRE_UTF8 flag, the strings passed as patterns and subjects +are checked for validity on entry to the relevant functions. If an invalid +UTF-8 string is passed, an error return is given. In some situations, you may +already know that your strings are valid, and therefore want to skip these +checks in order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag +at compile time or at run time, PCRE assumes that the pattern or subject it +is given (respectively) contains only valid UTF-8 codes. In this case, it does +not diagnose an invalid UTF-8 string. If you pass an invalid UTF-8 string to +PCRE when PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program +may crash. +</P> +<P> +2. In a pattern, the escape sequence \x{...}, where the contents of the braces +is a string of hexadecimal digits, is interpreted as a UTF-8 character whose +code number is the given hexadecimal number, for example: \x{1234}. If a +non-hexadecimal digit appears between the braces, the item is not recognized. +This escape sequence can be used either as a literal, or within a character +class. +</P> +<P> +3. The original hexadecimal escape sequence, \xhh, matches a two-byte UTF-8 +character if the value is greater than 127. +</P> +<P> +4. Repeat quantifiers apply to complete UTF-8 characters, not to individual +bytes, for example: \x{100}{3}. +</P> +<P> +5. The dot metacharacter matches one UTF-8 character instead of a single byte. +</P> +<P> +6. The escape sequence \C can be used to match a single byte in UTF-8 mode, +but its use can lead to some strange effects. +</P> +<P> +7. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly +test characters of any code value, but the characters that PCRE recognizes as +digits, spaces, or word characters remain the same set as before, all with +values less than 256. +</P> +<P> +8. Case-insensitive matching applies only to characters whose values are less +than 256. PCRE does not support the notion of "case" for higher-valued +characters. +</P> +<P> +9. PCRE does not support the use of Unicode tables and properties or the Perl +escapes \p, \P, and \X. +</P> +<br><a name="SEC5" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel <ph10@cam.ac.uk> +<br> +University Computing Service, +<br> +Cambridge CB2 3QG, England. +<br> +Phone: +44 1223 334714 +</P> +<P> +Last updated: 20 August 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcre_compile.html b/external-libs/pcre/doc/html/pcre_compile.html new file mode 100644 index 00000000..e1a43793 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_compile.html @@ -0,0 +1,71 @@ +<html> +<head> +<title>pcre_compile specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b> +<b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b>const unsigned char *<i>tableptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function compiles a regular expression into an internal form. Its +arguments are: +</P> +<P> +<pre> + <i>pattern</i> A zero-terminated string containing the + regular expression to be compiled + <i>options</i> Zero or more option bits + <i>errptr</i> Where to put an error message + <i>erroffset</i> Offset in pattern where error was found + <i>tableptr</i> Pointer to character tables, or NULL to + use the built-in default +</PRE> +</P> +<P> +The option bits are: +</P> +<P> +<pre> + PCRE_ANCHORED Force pattern anchoring + PCRE_CASELESS Do caseless matching + PCRE_DOLLAR_ENDONLY $ not to match newline at end + PCRE_DOTALL . matches anything including NL + PCRE_EXTENDED Ignore whitespace and # comments + PCRE_EXTRA PCRE extra features + (not much use currently) + PCRE_MULTILINE ^ and $ match newlines within data + PCRE_NO_AUTO_CAPTURE Disable numbered capturing paren- + theses (named ones available) + PCRE_UNGREEDY Invert greediness of quantifiers + PCRE_UTF8 Run in UTF-8 mode + PCRE_NO_UTF8_CHECK Do not check the pattern for UTF-8 + validity (only relevant if + PCRE_UTF8 is set) +</PRE> +</P> +<P> +PCRE must be compiled with UTF-8 support in order to use PCRE_UTF8 +(or PCRE_NO_UTF8_CHECK). +</P> +<P> +The yield of the function is a pointer to a private data structure that +contains the compiled pattern, or NULL if an error was detected. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_config.html b/external-libs/pcre/doc/html/pcre_config.html new file mode 100644 index 00000000..3328b792 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_config.html @@ -0,0 +1,56 @@ +<html> +<head> +<title>pcre_config specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function makes it possible for a client program to find out which optional +features are available in the version of the PCRE library it is using. Its +arguments are as follows: +</P> +<P> +<pre> + <i>what</i> A code specifying what information is required + <i>where</i> Points to where to put the data +</PRE> +</P> +<P> +The available codes are: +</P> +<P> +<pre> + PCRE_CONFIG_LINK_SIZE Internal link size: 2, 3, or 4 + PCRE_CONFIG_MATCH_LIMIT Internal resource limit + PCRE_CONFIG_NEWLINE Value of the newline character + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + Threshold of return slots, above + which <b>malloc()</b> is used by + the POSIX API + PCRE_CONFIG_STACKRECURSE Recursion implementation (1=stack 0=heap) + PCRE_CONFIG_UTF8 Availability of UTF-8 support (1=yes 0=no) +</PRE> +</P> +<P> +The function yields 0 on success or PCRE_ERROR_BADOPTION otherwise. +</P> +<P> +There is a complete description of the PCRE native API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page, and a description of the POSIX API in the +<a href="pcreposix.html"><b>pcreposix</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_copy_named_substring.html b/external-libs/pcre/doc/html/pcre_copy_named_substring.html new file mode 100644 index 00000000..3b1da364 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_copy_named_substring.html @@ -0,0 +1,46 @@ +<html> +<head> +<title>pcre_copy_named_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b> +<b>const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b>char *<i>buffer</i>, int <i>buffersize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring, identified +by name, into a given buffer. The arguments are: +</P> +<P> +<pre> + <i>code</i> Pattern that was successfully matched + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre_exec()</b> + <i>stringname</i> Name of the required substring + <i>buffer</i> Buffer to receive the string + <i>buffersize</i> Size of buffer +</PRE> +</P> +<P> +The yield is the length of the substring, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string name is invalid. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_copy_substring.html b/external-libs/pcre/doc/html/pcre_copy_substring.html new file mode 100644 index 00000000..f5b9b553 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_copy_substring.html @@ -0,0 +1,44 @@ +<html> +<head> +<title>pcre_copy_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b> +<b>int <i>buffersize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring into a given +buffer. The arguments are: +</P> +<P> +<pre> + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre_exec()</b> + <i>stringnumber</i> Number of the required substring + <i>buffer</i> Buffer to receive the string + <i>buffersize</i> Size of buffer +</PRE> +</P> +<P> +The yield is the legnth of the string, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string number is invalid. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_exec.html b/external-libs/pcre/doc/html/pcre_exec.html new file mode 100644 index 00000000..cf86dfda --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_exec.html @@ -0,0 +1,58 @@ +<html> +<head> +<title>pcre_exec specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function matches a compiled regular expression against a given subject +string, and returns offsets to capturing subexpressions. Its arguments are: +</P> +<P> +<pre> + <i>code</i> Points to the compiled pattern + <i>extra</i> Points to an associated <b>pcre_extra</b> structure, + or is NULL + <i>subject</i> Points to the subject string + <i>length</i> Length of the subject string, in bytes + <i>startoffset</i> Offset in bytes in the subject at which to + start matching + <i>options</i> Option bits + <i>ovector</i> Points to a vector of ints for result offsets + <i>ovecsize</i> Size of the vector (a multiple of 3) +</PRE> +</P> +<P> +The options are: +</P> +<P> +<pre> + PCRE_ANCHORED Match only at the first position + PCRE_NOTBOL Subject is not the beginning of a line + PCRE_NOTEOL Subject is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) +</PRE> +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_free_substring.html b/external-libs/pcre/doc/html/pcre_free_substring.html new file mode 100644 index 00000000..08b16078 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_free_substring.html @@ -0,0 +1,29 @@ +<html> +<head> +<title>pcre_free_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_free_substring(const char *<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for freeing the store obtained by a previous +call to <b>pcre_get_substring()</b> or <b>pcre_get_named_substring()</b>. Its +only argument is a pointer to the string. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_free_substring_list.html b/external-libs/pcre/doc/html/pcre_free_substring_list.html new file mode 100644 index 00000000..c130f281 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_free_substring_list.html @@ -0,0 +1,29 @@ +<html> +<head> +<title>pcre_free_substring_list specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for freeing the store obtained by a previous +call to <b>pcre_get_substring_list()</b>. Its only argument is a pointer to the +list of string pointers. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_fullinfo.html b/external-libs/pcre/doc/html/pcre_fullinfo.html new file mode 100644 index 00000000..f43fa65f --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_fullinfo.html @@ -0,0 +1,68 @@ +<html> +<head> +<title>pcre_fullinfo specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b>int <i>what</i>, void *<i>where</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function returns information about a compiled pattern. Its arguments are: +</P> +<P> +<pre> + <i>code</i> Compiled regular expression + <i>extra</i> Result of <b>pcre_study()</b> or NULL + <i>what</i> What information is required + <i>where</i> Where to put the information +</PRE> +</P> +<P> +The following information is available: +</P> +<P> +<pre> + PCRE_INFO_BACKREFMAX Number of highest back reference + PCRE_INFO_CAPTURECOUNT Number of capturing subpatterns + PCRE_INFO_FIRSTBYTE Fixed first byte for a match, or + -1 for start of string + or after newline, or + -2 otherwise + PCRE_INFO_FIRSTTABLE Table of first bytes + (after studying) + PCRE_INFO_LASTLITERAL Literal last byte required + PCRE_INFO_NAMECOUNT Number of named subpatterns + PCRE_INFO_NAMEENTRYSIZE Size of name table entry + PCRE_INFO_NAMETABLE Pointer to name table + PCRE_INFO_OPTIONS Options used for compilation + PCRE_INFO_SIZE Size of compiled pattern +</PRE> +</P> +<P> +The yield of the function is zero on success or: +</P> +<P> +<pre> + PCRE_ERROR_NULL the argument <i>code</i> was NULL + the argument <i>where</i> was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid +</PRE> +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_get_named_substring.html b/external-libs/pcre/doc/html/pcre_get_named_substring.html new file mode 100644 index 00000000..89a2beeb --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_get_named_substring.html @@ -0,0 +1,46 @@ +<html> +<head> +<title>pcre_get_named_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_named_substring(const pcre *<i>code</i>,</b> +<b>const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b>const char **<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring by name. The +arguments are: +</P> +<P> +<pre> + <i>code</i> Compiled pattern + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre_exec()</b> + <i>stringname</i> Name of the required substring + <i>stringptr</i> Where to put the string pointer +</PRE> +</P> +<P> +The yield is the length of the extracted substring, PCRE_ERROR_NOMEMORY if +sufficient memory could not be obtained, or PCRE_ERROR_NOSUBSTRING if the +string name is invalid. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_get_stringnumber.html b/external-libs/pcre/doc/html/pcre_get_stringnumber.html new file mode 100644 index 00000000..ee1c0a9c --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_get_stringnumber.html @@ -0,0 +1,39 @@ +<html> +<head> +<title>pcre_get_stringnumber specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b>const char *<i>name</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This convenience function finds the number of a named substring capturing +parenthesis in a compiled pattern. Its arguments are: +</P> +<P> +<pre> + <i>code</i> Compiled regular expression + <i>name</i> Name whose number is required +</PRE> +</P> +<P> +The yield of the function is the number of the parenthesis if the name is +found, or PCRE_ERROR_NOSUBSTRING otherwise. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_get_substring.html b/external-libs/pcre/doc/html/pcre_get_substring.html new file mode 100644 index 00000000..2a55c10f --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_get_substring.html @@ -0,0 +1,44 @@ +<html> +<head> +<title>pcre_get_substring specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b>const char **<i>stringptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a captured substring. The +arguments are: +</P> +<P> +<pre> + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre_exec()</b> used + <i>stringcount</i> Value returned by <b>pcre_exec()</b> + <i>stringnumber</i> Number of the required substring + <i>stringptr</i> Where to put the string pointer +</PRE> +</P> +<P> +The yield is the length of the substring, PCRE_ERROR_NOMEMORY if sufficient +memory could not be obtained, or PCRE_ERROR_NOSUBSTRING if the string number is +invalid. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_get_substring_list.html b/external-libs/pcre/doc/html/pcre_get_substring_list.html new file mode 100644 index 00000000..7e91f56b --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_get_substring_list.html @@ -0,0 +1,41 @@ +<html> +<head> +<title>pcre_get_substring_list specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This is a convenience function for extracting a list of all the captured +substrings. The arguments are: +</P> +<P> +<pre> + <i>subject</i> Subject that has been successfully matched + <i>ovector</i> Offset vector that <b>pcre_exec</b> used + <i>stringcount</i> Value returned by <b>pcre_exec</b> + <i>listptr</i> Where to put a pointer to the list +</PRE> +</P> +<P> +The yield is zero on success or PCRE_ERROR_NOMEMORY if sufficient memory could +not be obtained. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_info.html b/external-libs/pcre/doc/html/pcre_info.html new file mode 100644 index 00000000..97fc59b4 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_info.html @@ -0,0 +1,28 @@ +<html> +<head> +<title>pcre_info specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b> +<b>*<i>firstcharptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function is obsolete. You should be using <b>pcre_fullinfo()</b> instead. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_maketables.html b/external-libs/pcre/doc/html/pcre_maketables.html new file mode 100644 index 00000000..ba3e026b --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_maketables.html @@ -0,0 +1,31 @@ +<html> +<head> +<title>pcre_maketables specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>const unsigned char *pcre_maketables(void);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function builds a set of character tables which can be passed to +<b>pcre_compile()</b> to override PCRE's internal, built-in tables (which were +made by <b>pcre_maketables()</b> when PCRE was compiled). You might want to do +this if you are using a non-standard locale. The function yields a pointer to +the tables. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_study.html b/external-libs/pcre/doc/html/pcre_study.html new file mode 100644 index 00000000..f3727d1f --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_study.html @@ -0,0 +1,45 @@ +<html> +<head> +<title>pcre_study specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b>const char **<i>errptr</i>);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function studies a compiled pattern, to see if additional information can +be extracted that might speed up matching. Its arguments are: +</P> +<P> +<pre> + <i>code</i> A compiled regular expression + <i>options</i> Options for <b>pcre_study()</b> + <i>errptr</i> Where to put an error message +</PRE> +</P> +<P> +If the function returns NULL, either it could not find any additional +information, or there was an error. You can tell the difference by looking at +the error value. It is NULL in first case. +</P> +<P> +There are currently no options defined; the value of the second argument should +always be zero. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcre_version.html b/external-libs/pcre/doc/html/pcre_version.html new file mode 100644 index 00000000..35c47cd6 --- /dev/null +++ b/external-libs/pcre/doc/html/pcre_version.html @@ -0,0 +1,28 @@ +<html> +<head> +<title>pcre_version specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<br><b> +SYNOPSIS +</b><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>char *pcre_version(void);</b> +</P> +<br><b> +DESCRIPTION +</b><br> +<P> +This function returns a character string that gives the version number of the +PCRE library, and its date of release. +</P> +<P> +There is a complete description of the PCRE API in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page. diff --git a/external-libs/pcre/doc/html/pcreapi.html b/external-libs/pcre/doc/html/pcreapi.html new file mode 100644 index 00000000..8ae6fb1e --- /dev/null +++ b/external-libs/pcre/doc/html/pcreapi.html @@ -0,0 +1,1346 @@ +<html> +<head> +<title>pcreapi specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS OF PCRE API</a> +<li><a name="TOC2" href="#SEC2">PCRE API</a> +<li><a name="TOC3" href="#SEC3">MULTITHREADING</a> +<li><a name="TOC4" href="#SEC4">CHECKING BUILD-TIME OPTIONS</a> +<li><a name="TOC5" href="#SEC5">COMPILING A PATTERN</a> +<li><a name="TOC6" href="#SEC6">STUDYING A PATTERN</a> +<li><a name="TOC7" href="#SEC7">LOCALE SUPPORT</a> +<li><a name="TOC8" href="#SEC8">INFORMATION ABOUT A PATTERN</a> +<li><a name="TOC9" href="#SEC9">OBSOLETE INFO FUNCTION</a> +<li><a name="TOC10" href="#SEC10">MATCHING A PATTERN</a> +<li><a name="TOC11" href="#SEC11">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a> +<li><a name="TOC12" href="#SEC12">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS OF PCRE API</a><br> +<P> +<b>#include <pcre.h></b> +</P> +<P> +<b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b> +<b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b>const unsigned char *<i>tableptr</i>);</b> +</P> +<P> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b>const char **<i>errptr</i>);</b> +</P> +<P> +<b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +</P> +<P> +<b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b> +<b>const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b>char *<i>buffer</i>, int <i>buffersize</i>);</b> +</P> +<P> +<b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b> +<b>int <i>buffersize</i>);</b> +</P> +<P> +<b>int pcre_get_named_substring(const pcre *<i>code</i>,</b> +<b>const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b>const char **<i>stringptr</i>);</b> +</P> +<P> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b>const char *<i>name</i>);</b> +</P> +<P> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b>const char **<i>stringptr</i>);</b> +</P> +<P> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +</P> +<P> +<b>void pcre_free_substring(const char *<i>stringptr</i>);</b> +</P> +<P> +<b>void pcre_free_substring_list(const char **<i>stringptr</i>);</b> +</P> +<P> +<b>const unsigned char *pcre_maketables(void);</b> +</P> +<P> +<b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b>int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +<b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b> +<b>*<i>firstcharptr</i>);</b> +</P> +<P> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +<b>char *pcre_version(void);</b> +</P> +<P> +<b>void *(*pcre_malloc)(size_t);</b> +</P> +<P> +<b>void (*pcre_free)(void *);</b> +</P> +<P> +<b>void *(*pcre_stack_malloc)(size_t);</b> +</P> +<P> +<b>void (*pcre_stack_free)(void *);</b> +</P> +<P> +<b>int (*pcre_callout)(pcre_callout_block *);</b> +</P> +<br><a name="SEC2" href="#TOC1">PCRE API</a><br> +<P> +PCRE has its own native API, which is described in this document. There is also +a set of wrapper functions that correspond to the POSIX regular expression API. +These are described in the <b>pcreposix</b> documentation. +</P> +<P> +The native API function prototypes are defined in the header file <b>pcre.h</b>, +and on Unix systems the library itself is called <b>libpcre.a</b>, so can be +accessed by adding <b>-lpcre</b> to the command for linking an application which +calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to +contain the major and minor release numbers for the library. Applications can +use these to include support for different releases. +</P> +<P> +The functions <b>pcre_compile()</b>, <b>pcre_study()</b>, and <b>pcre_exec()</b> +are used for compiling and matching regular expressions. A sample program that +demonstrates the simplest way of using them is given in the file +<i>pcredemo.c</i>. The <b>pcresample</b> documentation describes how to run it. +</P> +<P> +There are convenience functions for extracting captured substrings from a +matched subject string. They are: +</P> +<P> +<pre> + <b>pcre_copy_substring()</b> + <b>pcre_copy_named_substring()</b> + <b>pcre_get_substring()</b> + <b>pcre_get_named_substring()</b> + <b>pcre_get_substring_list()</b> +</PRE> +</P> +<P> +<b>pcre_free_substring()</b> and <b>pcre_free_substring_list()</b> are also +provided, to free the memory used for extracted strings. +</P> +<P> +The function <b>pcre_maketables()</b> is used (optionally) to build a set of +character tables in the current locale for passing to <b>pcre_compile()</b>. +</P> +<P> +The function <b>pcre_fullinfo()</b> is used to find out information about a +compiled pattern; <b>pcre_info()</b> is an obsolete version which returns only +some of the available information, but is retained for backwards compatibility. +The function <b>pcre_version()</b> returns a pointer to a string containing the +version of PCRE and its date of release. +</P> +<P> +The global variables <b>pcre_malloc</b> and <b>pcre_free</b> initially contain +the entry points of the standard <b>malloc()</b> and <b>free()</b> functions +respectively. PCRE calls the memory management functions via these variables, +so a calling program can replace them if it wishes to intercept the calls. This +should be done before calling any PCRE functions. +</P> +<P> +The global variables <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are also +indirections to memory management functions. These special functions are used +only when PCRE is compiled to use the heap for remembering data, instead of +recursive function calls. This is a non-standard way of building PCRE, for use +in environments that have limited stacks. Because of the greater use of memory +management, it runs more slowly. Separate functions are provided so that +special-purpose external code can be used for this case. When used, these +functions are always called in a stack-like manner (last obtained, first +freed), and always for memory blocks of the same size. +</P> +<P> +The global variable <b>pcre_callout</b> initially contains NULL. It can be set +by the caller to a "callout" function, which PCRE will then call at specified +points during a matching operation. Details are given in the <b>pcrecallout</b> +documentation. +</P> +<br><a name="SEC3" href="#TOC1">MULTITHREADING</a><br> +<P> +The PCRE functions can be used in multi-threading applications, with the +proviso that the memory management functions pointed to by <b>pcre_malloc</b>, +<b>pcre_free</b>, <b>pcre_stack_malloc</b>, and <b>pcre_stack_free</b>, and the +callout function pointed to by <b>pcre_callout</b>, are shared by all threads. +</P> +<P> +The compiled form of a regular expression is not altered during matching, so +the same compiled pattern can safely be used by several threads at once. +</P> +<br><a name="SEC4" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> +<P> +<b>int pcre_config(int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +The function <b>pcre_config()</b> makes it possible for a PCRE client to +discover which optional features have been compiled into the PCRE library. The +<a href="pcrebuild.html"><b>pcrebuild</b></a> +documentation has more details about these optional features. +</P> +<P> +The first argument for <b>pcre_config()</b> is an integer, specifying which +information is required; the second argument is a pointer to a variable into +which the information is placed. The following information is available: +</P> +<P> +<pre> + PCRE_CONFIG_UTF8 +</PRE> +</P> +<P> +The output is an integer that is set to one if UTF-8 support is available; +otherwise it is set to zero. +</P> +<P> +<pre> + PCRE_CONFIG_NEWLINE +</PRE> +</P> +<P> +The output is an integer that is set to the value of the code that is used for +the newline character. It is either linefeed (10) or carriage return (13), and +should normally be the standard character for your operating system. +</P> +<P> +<pre> + PCRE_CONFIG_LINK_SIZE +</PRE> +</P> +<P> +The output is an integer that contains the number of bytes used for internal +linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values +allow larger regular expressions to be compiled, at the expense of slower +matching. The default value of 2 is sufficient for all but the most massive +patterns, since it allows the compiled pattern to be up to 64K in size. +</P> +<P> +<pre> + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD +</PRE> +</P> +<P> +The output is an integer that contains the threshold above which the POSIX +interface uses <b>malloc()</b> for output vectors. Further details are given in +the <b>pcreposix</b> documentation. +</P> +<P> +<pre> + PCRE_CONFIG_MATCH_LIMIT +</PRE> +</P> +<P> +The output is an integer that gives the default limit for the number of +internal matching function calls in a <b>pcre_exec()</b> execution. Further +details are given with <b>pcre_exec()</b> below. +</P> +<P> +<pre> + PCRE_CONFIG_STACKRECURSE +</PRE> +</P> +<P> +The output is an integer that is set to one if internal recursion is +implemented by recursive function calls that use the stack to remember their +state. This is the usual way that PCRE is compiled. The output is zero if PCRE +was compiled to use blocks of data on the heap instead of recursive function +calls. In this case, <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> are +called to manage memory blocks on the heap, thus avoiding the use of the stack. +</P> +<br><a name="SEC5" href="#TOC1">COMPILING A PATTERN</a><br> +<P> +<b>pcre *pcre_compile(const char *<i>pattern</i>, int <i>options</i>,</b> +<b>const char **<i>errptr</i>, int *<i>erroffset</i>,</b> +<b>const unsigned char *<i>tableptr</i>);</b> +</P> +<P> +The function <b>pcre_compile()</b> is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument <i>pattern</i>. A pointer to a single block of memory +that is obtained via <b>pcre_malloc</b> is returned. This contains the compiled +code and related data. The <b>pcre</b> type is defined for the returned block; +this is a typedef for a structure whose contents are not externally defined. It +is up to the caller to free the memory when it is no longer required. +</P> +<P> +Although the compiled code of a PCRE regex is relocatable, that is, it does not +depend on memory location, the complete <b>pcre</b> data block is not +fully relocatable, because it contains a copy of the <i>tableptr</i> argument, +which is an address (see below). +</P> +<P> +The <i>options</i> argument contains independent bits that affect the +compilation. It should be zero if no options are required. Some of the options, +in particular, those that are compatible with Perl, can also be set and unset +from within the pattern (see the detailed description of regular expressions +in the <b>pcrepattern</b> documentation). For these options, the contents of the +<i>options</i> argument specifies their initial settings at the start of +compilation and execution. The PCRE_ANCHORED option can be set at the time of +matching as well as at compile time. +</P> +<P> +If <i>errptr</i> is NULL, <b>pcre_compile()</b> returns NULL immediately. +Otherwise, if compilation of a pattern fails, <b>pcre_compile()</b> returns +NULL, and sets the variable pointed to by <i>errptr</i> to point to a textual +error message. The offset from the start of the pattern to the character where +the error was discovered is placed in the variable pointed to by +<i>erroffset</i>, which must not be NULL. If it is, an immediate error is given. +</P> +<P> +If the final argument, <i>tableptr</i>, is NULL, PCRE uses a default set of +character tables which are built when it is compiled, using the default C +locale. Otherwise, <i>tableptr</i> must be the result of a call to +<b>pcre_maketables()</b>. See the section on locale support below. +</P> +<P> +This code fragment shows a typical straightforward call to <b>pcre_compile()</b>: +</P> +<P> +<pre> + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ +</PRE> +</P> +<P> +The following option bits are defined: +</P> +<P> +<pre> + PCRE_ANCHORED +</PRE> +</P> +<P> +If this bit is set, the pattern is forced to be "anchored", that is, it is +constrained to match only at the first matching point in the string which is +being searched (the "subject string"). This effect can also be achieved by +appropriate constructs in the pattern itself, which is the only way to do it in +Perl. +</P> +<P> +<pre> + PCRE_CASELESS +</PRE> +</P> +<P> +If this bit is set, letters in the pattern match both upper and lower case +letters. It is equivalent to Perl's /i option, and it can be changed within a +pattern by a (?i) option setting. +</P> +<P> +<pre> + PCRE_DOLLAR_ENDONLY +</PRE> +</P> +<P> +If this bit is set, a dollar metacharacter in the pattern matches only at the +end of the subject string. Without this option, a dollar also matches +immediately before the final character if it is a newline (but not before any +other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is +set. There is no equivalent to this option in Perl, and no way to set it within +a pattern. +</P> +<P> +<pre> + PCRE_DOTALL +</PRE> +</P> +<P> +If this bit is set, a dot metacharater in the pattern matches all characters, +including newlines. Without it, newlines are excluded. This option is +equivalent to Perl's /s option, and it can be changed within a pattern by a +(?s) option setting. A negative class such as [^a] always matches a newline +character, independent of the setting of this option. +</P> +<P> +<pre> + PCRE_EXTENDED +</PRE> +</P> +<P> +If this bit is set, whitespace data characters in the pattern are totally +ignored except when escaped or inside a character class. Whitespace does not +include the VT character (code 11). In addition, characters between an +unescaped # outside a character class and the next newline character, +inclusive, are also ignored. This is equivalent to Perl's /x option, and it can +be changed within a pattern by a (?x) option setting. +</P> +<P> +This option makes it possible to include comments inside complicated patterns. +Note, however, that this applies only to data characters. Whitespace characters +may never appear within special character sequences in a pattern, for example +within the sequence (?( which introduces a conditional subpattern. +</P> +<P> +<pre> + PCRE_EXTRA +</PRE> +</P> +<P> +This option was invented in order to turn on additional functionality of PCRE +that is incompatible with Perl, but it is currently of very little use. When +set, any backslash in a pattern that is followed by a letter that has no +special meaning causes an error, thus reserving these combinations for future +expansion. By default, as in Perl, a backslash followed by a letter with no +special meaning is treated as a literal. There are at present no other features +controlled by this option. It can also be set by a (?X) option setting within a +pattern. +</P> +<P> +<pre> + PCRE_MULTILINE +</PRE> +</P> +<P> +By default, PCRE treats the subject string as consisting of a single "line" of +characters (even if it actually contains several newlines). The "start of line" +metacharacter (^) matches only at the start of the string, while the "end of +line" metacharacter ($) matches only at the end of the string, or before a +terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as +Perl. +</P> +<P> +When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs +match immediately following or immediately before any newline in the subject +string, respectively, as well as at the very start and end. This is equivalent +to Perl's /m option, and it can be changed within a pattern by a (?m) option +setting. If there are no "\n" characters in a subject string, or no +occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. +</P> +<P> +<pre> + PCRE_NO_AUTO_CAPTURE +</PRE> +</P> +<P> +If this option is set, it disables the use of numbered capturing parentheses in +the pattern. Any opening parenthesis that is not followed by ? behaves as if it +were followed by ?: but named parentheses can still be used for capturing (and +they acquire numbers in the usual way). There is no equivalent of this option +in Perl. +</P> +<P> +<pre> + PCRE_UNGREEDY +</PRE> +</P> +<P> +This option inverts the "greediness" of the quantifiers so that they are not +greedy by default, but become greedy if followed by "?". It is not compatible +with Perl. It can also be set by a (?U) option setting within the pattern. +</P> +<P> +<pre> + PCRE_UTF8 +</PRE> +</P> +<P> +This option causes PCRE to regard both the pattern and the subject as strings +of UTF-8 characters instead of single-byte character strings. However, it is +available only if PCRE has been built to include UTF-8 support. If not, the use +of this option provokes an error. Details of how this option changes the +behaviour of PCRE are given in the +<a href="pcre.html#utf8support">section on UTF-8 support</a> +in the main +<a href="pcre.html"><b>pcre</b></a> +page. +</P> +<P> +<pre> + PCRE_NO_UTF8_CHECK +</PRE> +</P> +<P> +When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is +automatically checked. If an invalid UTF-8 sequence of bytes is found, +<b>pcre_compile()</b> returns an error. If you already know that your pattern is +valid, and you want to skip this check for performance reasons, you can set the +PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid +UTF-8 string as a pattern is undefined. It may cause your program to crash. +Note that there is a similar option for suppressing the checking of subject +strings passed to <b>pcre_exec()</b>. +</P> +<br><a name="SEC6" href="#TOC1">STUDYING A PATTERN</a><br> +<P> +<b>pcre_extra *pcre_study(const pcre *<i>code</i>, int <i>options</i>,</b> +<b>const char **<i>errptr</i>);</b> +</P> +<P> +When a pattern is going to be used several times, it is worth spending more +time analyzing it in order to speed up the time taken for matching. The +function <b>pcre_study()</b> takes a pointer to a compiled pattern as its first +argument. If studing the pattern produces additional information that will help +speed up matching, <b>pcre_study()</b> returns a pointer to a <b>pcre_extra</b> +block, in which the <i>study_data</i> field points to the results of the study. +</P> +<P> +The returned value from a <b>pcre_study()</b> can be passed directly to +<b>pcre_exec()</b>. However, the <b>pcre_extra</b> block also contains other +fields that can be set by the caller before the block is passed; these are +described below. If studying the pattern does not produce any additional +information, <b>pcre_study()</b> returns NULL. In that circumstance, if the +calling program wants to pass some of the other fields to <b>pcre_exec()</b>, it +must set up its own <b>pcre_extra</b> block. +</P> +<P> +The second argument contains option bits. At present, no options are defined +for <b>pcre_study()</b>, and this argument should always be zero. +</P> +<P> +The third argument for <b>pcre_study()</b> is a pointer for an error message. If +studying succeeds (even if no data is returned), the variable it points to is +set to NULL. Otherwise it points to a textual error message. You should +therefore test the error pointer for NULL after calling <b>pcre_study()</b>, to +be sure that it has run successfully. +</P> +<P> +This is a typical call to <b>pcre_study</b>(): +</P> +<P> +<pre> + pcre_extra *pe; + pe = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options exist */ + &error); /* set to NULL or points to a message */ +</PRE> +</P> +<P> +At present, studying a pattern is useful only for non-anchored patterns that do +not have a single fixed starting character. A bitmap of possible starting +characters is created. +</P> +<a name="localesupport"></a><br><a name="SEC7" href="#TOC1">LOCALE SUPPORT</a><br> +<P> +PCRE handles caseless matching, and determines whether characters are letters, +digits, or whatever, by reference to a set of tables. When running in UTF-8 +mode, this applies only to characters with codes less than 256. The library +contains a default set of tables that is created in the default C locale when +PCRE is compiled. This is used when the final argument of <b>pcre_compile()</b> +is NULL, and is sufficient for many applications. +</P> +<P> +An alternative set of tables can, however, be supplied. Such tables are built +by calling the <b>pcre_maketables()</b> function, which has no arguments, in the +relevant locale. The result can then be passed to <b>pcre_compile()</b> as often +as necessary. For example, to build and use tables that are appropriate for the +French locale (where accented characters with codes greater than 128 are +treated as letters), the following code could be used: +</P> +<P> +<pre> + setlocale(LC_CTYPE, "fr"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); +</PRE> +</P> +<P> +The tables are built in memory that is obtained via <b>pcre_malloc</b>. The +pointer that is passed to <b>pcre_compile</b> is saved with the compiled +pattern, and the same tables are used via this pointer by <b>pcre_study()</b> +and <b>pcre_exec()</b>. Thus, for any single pattern, compilation, studying and +matching all happen in the same locale, but different patterns can be compiled +in different locales. It is the caller's responsibility to ensure that the +memory containing the tables remains available for as long as it is needed. +</P> +<br><a name="SEC8" href="#TOC1">INFORMATION ABOUT A PATTERN</a><br> +<P> +<b>int pcre_fullinfo(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b>int <i>what</i>, void *<i>where</i>);</b> +</P> +<P> +The <b>pcre_fullinfo()</b> function returns information about a compiled +pattern. It replaces the obsolete <b>pcre_info()</b> function, which is +nevertheless retained for backwards compability (and is documented below). +</P> +<P> +The first argument for <b>pcre_fullinfo()</b> is a pointer to the compiled +pattern. The second argument is the result of <b>pcre_study()</b>, or NULL if +the pattern was not studied. The third argument specifies which piece of +information is required, and the fourth argument is a pointer to a variable +to receive the data. The yield of the function is zero for success, or one of +the following negative numbers: +</P> +<P> +<pre> + PCRE_ERROR_NULL the argument <i>code</i> was NULL + the argument <i>where</i> was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of <i>what</i> was invalid +</PRE> +</P> +<P> +Here is a typical call of <b>pcre_fullinfo()</b>, to obtain the length of the +compiled pattern: +</P> +<P> +<pre> + int rc; + unsigned long int length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + pe, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ +</PRE> +</P> +<P> +The possible values for the third argument are defined in <b>pcre.h</b>, and are +as follows: +</P> +<P> +<pre> + PCRE_INFO_BACKREFMAX +</PRE> +</P> +<P> +Return the number of the highest back reference in the pattern. The fourth +argument should point to an <b>int</b> variable. Zero is returned if there are +no back references. +</P> +<P> +<pre> + PCRE_INFO_CAPTURECOUNT +</PRE> +</P> +<P> +Return the number of capturing subpatterns in the pattern. The fourth argument +should point to an \fbint\fR variable. +</P> +<P> +<pre> + PCRE_INFO_FIRSTBYTE +</PRE> +</P> +<P> +Return information about the first byte of any matched string, for a +non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the +old name is still recognized for backwards compatibility.) +</P> +<P> +If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote), +it is returned in the integer pointed to by <i>where</i>. Otherwise, if either +</P> +<P> +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or +</P> +<P> +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), +</P> +<P> +-1 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise -2 is +returned. For anchored patterns, -2 is returned. +</P> +<P> +<pre> + PCRE_INFO_FIRSTTABLE +</PRE> +</P> +<P> +If the pattern was studied, and this resulted in the construction of a 256-bit +table indicating a fixed set of bytes for the first byte in any matching +string, a pointer to the table is returned. Otherwise NULL is returned. The +fourth argument should point to an <b>unsigned char *</b> variable. +</P> +<P> +<pre> + PCRE_INFO_LASTLITERAL +</PRE> +</P> +<P> +Return the value of the rightmost literal byte that must exist in any matched +string, other than at its start, if such a byte has been recorded. The fourth +argument should point to an <b>int</b> variable. If there is no such byte, -1 is +returned. For anchored patterns, a last literal byte is recorded only if it +follows something of variable length. For example, for the pattern +/^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value +is -1. +</P> +<P> +<pre> + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE +</PRE> +</P> +<P> +PCRE supports the use of named as well as numbered capturing parentheses. The +names are just an additional way of identifying the parentheses, which still +acquire a number. A caller that wants to extract data from a named subpattern +must convert the name to a number in order to access the correct pointers in +the output vector (described with <b>pcre_exec()</b> below). In order to do +this, it must first use these three values to obtain the name-to-number mapping +table for the pattern. +</P> +<P> +The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives +the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each +entry; both of these return an <b>int</b> value. The entry size depends on the +length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first +entry of the table (a pointer to <b>char</b>). The first two bytes of each entry +are the number of the capturing parenthesis, most significant byte first. The +rest of the entry is the corresponding name, zero terminated. The names are in +alphabetical order. For example, consider the following pattern (assume +PCRE_EXTENDED is set, so white space - including newlines - is ignored): +</P> +<P> +<pre> + (?P<date> (?P<year>(\d\d)?\d\d) - + (?P<month>\d\d) - (?P<day>\d\d) ) +</PRE> +</P> +<P> +There are four named subpatterns, so the table has four entries, and each entry +in the table is eight bytes long. The table is as follows, with non-printing +bytes shows in hex, and undefined bytes shown as ??: +</P> +<P> +<pre> + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? +</PRE> +</P> +<P> +When writing code to extract data from named subpatterns, remember that the +length of each entry may be different for each compiled pattern. +</P> +<P> +<pre> + PCRE_INFO_OPTIONS +</PRE> +</P> +<P> +Return a copy of the options with which the pattern was compiled. The fourth +argument should point to an <b>unsigned long int</b> variable. These option bits +are those specified in the call to <b>pcre_compile()</b>, modified by any +top-level option settings within the pattern itself. +</P> +<P> +A pattern is automatically anchored by PCRE if all of its top-level +alternatives begin with one of the following: +</P> +<P> +<pre> + ^ unless PCRE_MULTILINE is set + \A always + \G always + .* if PCRE_DOTALL is set and there are no back + references to the subpattern in which .* appears +</PRE> +</P> +<P> +For such patterns, the PCRE_ANCHORED bit is set in the options returned by +<b>pcre_fullinfo()</b>. +</P> +<P> +<pre> + PCRE_INFO_SIZE +</PRE> +</P> +<P> +Return the size of the compiled pattern, that is, the value that was passed as +the argument to <b>pcre_malloc()</b> when PCRE was getting memory in which to +place the compiled data. The fourth argument should point to a <b>size_t</b> +variable. +</P> +<P> +<pre> + PCRE_INFO_STUDYSIZE +</PRE> +</P> +<P> +Returns the size of the data block pointed to by the <i>study_data</i> field in +a <b>pcre_extra</b> block. That is, it is the value that was passed to +<b>pcre_malloc()</b> when PCRE was getting memory into which to place the data +created by <b>pcre_study()</b>. The fourth argument should point to a +<b>size_t</b> variable. +</P> +<br><a name="SEC9" href="#TOC1">OBSOLETE INFO FUNCTION</a><br> +<P> +<b>int pcre_info(const pcre *<i>code</i>, int *<i>optptr</i>, int</b> +<b>*<i>firstcharptr</i>);</b> +</P> +<P> +The <b>pcre_info()</b> function is now obsolete because its interface is too +restrictive to return all the available data about a compiled pattern. New +programs should use <b>pcre_fullinfo()</b> instead. The yield of +<b>pcre_info()</b> is the number of capturing subpatterns, or one of the +following negative numbers: +</P> +<P> +<pre> + PCRE_ERROR_NULL the argument <i>code</i> was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found +</PRE> +</P> +<P> +If the <i>optptr</i> argument is not NULL, a copy of the options with which the +pattern was compiled is placed in the integer it points to (see +PCRE_INFO_OPTIONS above). +</P> +<P> +If the pattern is not anchored and the <i>firstcharptr</i> argument is not NULL, +it is used to pass back information about the first character of any matched +string (see PCRE_INFO_FIRSTBYTE above). +</P> +<br><a name="SEC10" href="#TOC1">MATCHING A PATTERN</a><br> +<P> +<b>int pcre_exec(const pcre *<i>code</i>, const pcre_extra *<i>extra</i>,</b> +<b>const char *<i>subject</i>, int <i>length</i>, int <i>startoffset</i>,</b> +<b>int <i>options</i>, int *<i>ovector</i>, int <i>ovecsize</i>);</b> +</P> +<P> +The function <b>pcre_exec()</b> is called to match a subject string against a +pre-compiled pattern, which is passed in the <i>code</i> argument. If the +pattern has been studied, the result of the study should be passed in the +<i>extra</i> argument. +</P> +<P> +Here is an example of a simple call to <b>pcre_exec()</b>: +</P> +<P> +<pre> + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector for substring information */ + 30); /* number of elements in the vector */ +</PRE> +</P> +<P> +If the <i>extra</i> argument is not NULL, it must point to a <b>pcre_extra</b> +data block. The <b>pcre_study()</b> function returns such a block (when it +doesn't return NULL), but you can also create one for yourself, and pass +additional information in it. The fields in the block are as follows: +</P> +<P> +<pre> + unsigned long int <i>flags</i>; + void *<i>study_data</i>; + unsigned long int <i>match_limit</i>; + void *<i>callout_data</i>; +</PRE> +</P> +<P> +The <i>flags</i> field is a bitmap that specifies which of the other fields +are set. The flag bits are: +</P> +<P> +<pre> + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_CALLOUT_DATA +</PRE> +</P> +<P> +Other flag bits should be set to zero. The <i>study_data</i> field is set in the +<b>pcre_extra</b> block that is returned by <b>pcre_study()</b>, together with +the appropriate flag bit. You should not set this yourself, but you can add to +the block by setting the other fields. +</P> +<P> +The <i>match_limit</i> field provides a means of preventing PCRE from using up a +vast amount of resources when running patterns that are not going to match, +but which have a very large number of possibilities in their search trees. The +classic example is the use of nested unlimited repeats. Internally, PCRE uses a +function called <b>match()</b> which it calls repeatedly (sometimes +recursively). The limit is imposed on the number of times this function is +called during a match, which has the effect of limiting the amount of recursion +and backtracking that can take place. For patterns that are not anchored, the +count starts from zero for each position in the subject string. +</P> +<P> +The default limit for the library can be set when PCRE is built; the default +default is 10 million, which handles all but the most extreme cases. You can +reduce the default by suppling <b>pcre_exec()</b> with a \fRpcre_extra\fR block +in which <i>match_limit</i> is set to a smaller value, and +PCRE_EXTRA_MATCH_LIMIT is set in the <i>flags</i> field. If the limit is +exceeded, <b>pcre_exec()</b> returns PCRE_ERROR_MATCHLIMIT. +</P> +<P> +The <i>pcre_callout</i> field is used in conjunction with the "callout" feature, +which is described in the <b>pcrecallout</b> documentation. +</P> +<P> +The PCRE_ANCHORED option can be passed in the <i>options</i> argument, whose +unused bits must be zero. This limits <b>pcre_exec()</b> to matching at the +first matching position. However, if a pattern was compiled with PCRE_ANCHORED, +or turned out to be anchored by virtue of its contents, it cannot be made +unachored at matching time. +</P> +<P> +When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8 +string is automatically checked, and the value of <i>startoffset</i> is also +checked to ensure that it points to the start of a UTF-8 character. If an +invalid UTF-8 sequence of bytes is found, <b>pcre_exec()</b> returns the error +PCRE_ERROR_BADUTF8. If <i>startoffset</i> contains an invalid value, +PCRE_ERROR_BADUTF8_OFFSET is returned. +</P> +<P> +If you already know that your subject is valid, and you want to skip these +checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when +calling <b>pcre_exec()</b>. You might want to do this for the second and +subsequent calls to <b>pcre_exec()</b> if you are making repeated calls to find +all the matches in a single subject string. However, you should be sure that +the value of <i>startoffset</i> points to the start of a UTF-8 character. When +PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a +subject, or a value of <i>startoffset</i> that does not point to the start of a +UTF-8 character, is undefined. Your program may crash. +</P> +<P> +There are also three further options that can be set only at matching time: +</P> +<P> +<pre> + PCRE_NOTBOL +</PRE> +</P> +<P> +The first character of the string is not the beginning of a line, so the +circumflex metacharacter should not match before it. Setting this without +PCRE_MULTILINE (at compile time) causes circumflex never to match. +</P> +<P> +<pre> + PCRE_NOTEOL +</PRE> +</P> +<P> +The end of the string is not the end of a line, so the dollar metacharacter +should not match it nor (except in multiline mode) a newline immediately before +it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never +to match. +</P> +<P> +<pre> + PCRE_NOTEMPTY +</PRE> +</P> +<P> +An empty string is not considered to be a valid match if this option is set. If +there are alternatives in the pattern, they are tried. If all the alternatives +match the empty string, the entire match fails. For example, if the pattern +</P> +<P> +<pre> + a?b? +</PRE> +</P> +<P> +is applied to a string not beginning with "a" or "b", it matches the empty +string at the start of the subject. With PCRE_NOTEMPTY set, this match is not +valid, so PCRE searches further into the string for occurrences of "a" or "b". +</P> +<P> +Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case +of a pattern match of the empty string within its <b>split()</b> function, and +when using the /g modifier. It is possible to emulate Perl's behaviour after +matching a null string by first trying the match again at the same offset with +PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see +below) and trying an ordinary match again. +</P> +<P> +The subject string is passed to <b>pcre_exec()</b> as a pointer in +<i>subject</i>, a length in <i>length</i>, and a starting byte offset in +<i>startoffset</i>. Unlike the pattern string, the subject may contain binary +zero bytes. When the starting offset is zero, the search for a match starts at +the beginning of the subject, and this is by far the most common case. +</P> +<P> +If the pattern was compiled with the PCRE_UTF8 option, the subject must be a +sequence of bytes that is a valid UTF-8 string, and the starting offset must +point to the beginning of a UTF-8 character. If an invalid UTF-8 string or +offset is passed, an error (either PCRE_ERROR_BADUTF8 or +PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option PCRE_NO_UTF8_CHECK is +set, in which case PCRE's behaviour is not defined. +</P> +<P> +A non-zero starting offset is useful when searching for another match in the +same subject by calling <b>pcre_exec()</b> again after a previous success. +Setting <i>startoffset</i> differs from just passing over a shortened string and +setting PCRE_NOTBOL in the case of a pattern that begins with any kind of +lookbehind. For example, consider the pattern +</P> +<P> +<pre> + \Biss\B +</PRE> +</P> +<P> +which finds occurrences of "iss" in the middle of words. (\B matches only if +the current position in the subject is not a word boundary.) When applied to +the string "Mississipi" the first call to <b>pcre_exec()</b> finds the first +occurrence. If <b>pcre_exec()</b> is called again with just the remainder of the +subject, namely "issipi", it does not match, because \B is always false at the +start of the subject, which is deemed to be a word boundary. However, if +<b>pcre_exec()</b> is passed the entire string again, but with <i>startoffset</i> +set to 4, it finds the second occurrence of "iss" because it is able to look +behind the starting point to discover that it is preceded by a letter. +</P> +<P> +If a non-zero starting offset is passed when the pattern is anchored, one +attempt to match at the given offset is tried. This can only succeed if the +pattern does not require the match to be at the start of the subject. +</P> +<P> +In general, a pattern matches a certain portion of the subject, and in +addition, further substrings from the subject may be picked out by parts of the +pattern. Following the usage in Jeffrey Friedl's book, this is called +"capturing" in what follows, and the phrase "capturing subpattern" is used for +a fragment of a pattern that picks out a substring. PCRE supports several other +kinds of parenthesized subpattern that do not cause substrings to be captured. +</P> +<P> +Captured substrings are returned to the caller via a vector of integer offsets +whose address is passed in <i>ovector</i>. The number of elements in the vector +is passed in <i>ovecsize</i>. The first two-thirds of the vector is used to pass +back captured substrings, each substring using a pair of integers. The +remaining third of the vector is used as workspace by <b>pcre_exec()</b> while +matching capturing subpatterns, and is not available for passing back +information. The length passed in <i>ovecsize</i> should always be a multiple of +three. If it is not, it is rounded down. +</P> +<P> +When a match has been successful, information about captured substrings is +returned in pairs of integers, starting at the beginning of <i>ovector</i>, and +continuing up to two-thirds of its length at the most. The first element of a +pair is set to the offset of the first character in a substring, and the second +is set to the offset of the first character after the end of a substring. The +first pair, <i>ovector[0]</i> and <i>ovector[1]</i>, identify the portion of the +subject string matched by the entire pattern. The next pair is used for the +first capturing subpattern, and so on. The value returned by <b>pcre_exec()</b> +is the number of pairs that have been set. If there are no capturing +subpatterns, the return value from a successful match is 1, indicating that +just the first pair of offsets has been set. +</P> +<P> +Some convenience functions are provided for extracting the captured substrings +as separate strings. These are described in the following section. +</P> +<P> +It is possible for an capturing subpattern number <i>n+1</i> to match some +part of the subject when subpattern <i>n</i> has not been used at all. For +example, if the string "abc" is matched against the pattern (a|(z))(bc) +subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset +values corresponding to the unused subpattern are set to -1. +</P> +<P> +If a capturing subpattern is matched repeatedly, it is the last portion of the +string that it matched that gets returned. +</P> +<P> +If the vector is too small to hold all the captured substrings, it is used as +far as possible (up to two-thirds of its length), and the function returns a +value of zero. In particular, if the substring offsets are not of interest, +<b>pcre_exec()</b> may be called with <i>ovector</i> passed as NULL and +<i>ovecsize</i> as zero. However, if the pattern contains back references and +the <i>ovector</i> isn't big enough to remember the related substrings, PCRE has +to get additional memory for use during matching. Thus it is usually advisable +to supply an <i>ovector</i>. +</P> +<P> +Note that <b>pcre_info()</b> can be used to find out how many capturing +subpatterns there are in a compiled pattern. The smallest size for +<i>ovector</i> that will allow for <i>n</i> captured substrings, in addition to +the offsets of the substring matched by the whole pattern, is (<i>n</i>+1)*3. +</P> +<P> +If <b>pcre_exec()</b> fails, it returns a negative number. The following are +defined in the header file: +</P> +<P> +<pre> + PCRE_ERROR_NOMATCH (-1) +</PRE> +</P> +<P> +The subject string did not match the pattern. +</P> +<P> +<pre> + PCRE_ERROR_NULL (-2) +</PRE> +</P> +<P> +Either <i>code</i> or <i>subject</i> was passed as NULL, or <i>ovector</i> was +NULL and <i>ovecsize</i> was not zero. +</P> +<P> +<pre> + PCRE_ERROR_BADOPTION (-3) +</PRE> +</P> +<P> +An unrecognized bit was set in the <i>options</i> argument. +</P> +<P> +<pre> + PCRE_ERROR_BADMAGIC (-4) +</PRE> +</P> +<P> +PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch +the case when it is passed a junk pointer. This is the error it gives when the +magic number isn't present. +</P> +<P> +<pre> + PCRE_ERROR_UNKNOWN_NODE (-5) +</PRE> +</P> +<P> +While running the pattern match, an unknown item was encountered in the +compiled pattern. This error could be caused by a bug in PCRE or by overwriting +of the compiled pattern. +</P> +<P> +<pre> + PCRE_ERROR_NOMEMORY (-6) +</PRE> +</P> +<P> +If a pattern contains back references, but the <i>ovector</i> that is passed to +<b>pcre_exec()</b> is not big enough to remember the referenced substrings, PCRE +gets a block of memory at the start of matching to use for this purpose. If the +call via <b>pcre_malloc()</b> fails, this error is given. The memory is freed at +the end of matching. +</P> +<P> +<pre> + PCRE_ERROR_NOSUBSTRING (-7) +</PRE> +</P> +<P> +This error is used by the <b>pcre_copy_substring()</b>, +<b>pcre_get_substring()</b>, and <b>pcre_get_substring_list()</b> functions (see +below). It is never returned by <b>pcre_exec()</b>. +</P> +<P> +<pre> + PCRE_ERROR_MATCHLIMIT (-8) +</PRE> +</P> +<P> +The recursion and backtracking limit, as specified by the <i>match_limit</i> +field in a <b>pcre_extra</b> structure (or defaulted) was reached. See the +description above. +</P> +<P> +<pre> + PCRE_ERROR_CALLOUT (-9) +</PRE> +</P> +<P> +This error is never generated by <b>pcre_exec()</b> itself. It is provided for +use by callout functions that want to yield a distinctive error code. See the +<b>pcrecallout</b> documentation for details. +</P> +<P> +<pre> + PCRE_ERROR_BADUTF8 (-10) +</PRE> +</P> +<P> +A string that contains an invalid UTF-8 byte sequence was passed as a subject. +</P> +<P> +<pre> + PCRE_ERROR_BADUTF8_OFFSET (-11) +</PRE> +</P> +<P> +The UTF-8 byte sequence that was passed as a subject was valid, but the value +of <i>startoffset</i> did not point to the beginning of a UTF-8 character. +</P> +<br><a name="SEC11" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> +<P> +<b>int pcre_copy_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, int <i>stringnumber</i>, char *<i>buffer</i>,</b> +<b>int <i>buffersize</i>);</b> +</P> +<P> +<b>int pcre_get_substring(const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, int <i>stringnumber</i>,</b> +<b>const char **<i>stringptr</i>);</b> +</P> +<P> +<b>int pcre_get_substring_list(const char *<i>subject</i>,</b> +<b>int *<i>ovector</i>, int <i>stringcount</i>, const char ***<i>listptr</i>);</b> +</P> +<P> +Captured substrings can be accessed directly by using the offsets returned by +<b>pcre_exec()</b> in <i>ovector</i>. For convenience, the functions +<b>pcre_copy_substring()</b>, <b>pcre_get_substring()</b>, and +<b>pcre_get_substring_list()</b> are provided for extracting captured substrings +as new, separate, zero-terminated strings. These functions identify substrings +by number. The next section describes functions for extracting named +substrings. A substring that contains a binary zero is correctly extracted and +has a further zero added on the end, but the result is not, of course, +a C string. +</P> +<P> +The first three arguments are the same for all three of these functions: +<i>subject</i> is the subject string which has just been successfully matched, +<i>ovector</i> is a pointer to the vector of integer offsets that was passed to +<b>pcre_exec()</b>, and <i>stringcount</i> is the number of substrings that were +captured by the match, including the substring that matched the entire regular +expression. This is the value returned by <b>pcre_exec</b> if it is greater than +zero. If <b>pcre_exec()</b> returned zero, indicating that it ran out of space +in <i>ovector</i>, the value passed as <i>stringcount</i> should be the size of +the vector divided by three. +</P> +<P> +The functions <b>pcre_copy_substring()</b> and <b>pcre_get_substring()</b> +extract a single substring, whose number is given as <i>stringnumber</i>. A +value of zero extracts the substring that matched the entire pattern, while +higher values extract the captured substrings. For <b>pcre_copy_substring()</b>, +the string is placed in <i>buffer</i>, whose length is given by +<i>buffersize</i>, while for <b>pcre_get_substring()</b> a new block of memory is +obtained via <b>pcre_malloc</b>, and its address is returned via +<i>stringptr</i>. The yield of the function is the length of the string, not +including the terminating zero, or one of +</P> +<P> +<pre> + PCRE_ERROR_NOMEMORY (-6) +</PRE> +</P> +<P> +The buffer was too small for <b>pcre_copy_substring()</b>, or the attempt to get +memory failed for <b>pcre_get_substring()</b>. +</P> +<P> +<pre> + PCRE_ERROR_NOSUBSTRING (-7) +</PRE> +</P> +<P> +There is no substring whose number is <i>stringnumber</i>. +</P> +<P> +The <b>pcre_get_substring_list()</b> function extracts all available substrings +and builds a list of pointers to them. All this is done in a single block of +memory which is obtained via <b>pcre_malloc</b>. The address of the memory block +is returned via <i>listptr</i>, which is also the start of the list of string +pointers. The end of the list is marked by a NULL pointer. The yield of the +function is zero if all went well, or +</P> +<P> +<pre> + PCRE_ERROR_NOMEMORY (-6) +</PRE> +</P> +<P> +if the attempt to get the memory block failed. +</P> +<P> +When any of these functions encounter a substring that is unset, which can +happen when capturing subpattern number <i>n+1</i> matches some part of the +subject, but subpattern <i>n</i> has not been used at all, they return an empty +string. This can be distinguished from a genuine zero-length substring by +inspecting the appropriate offset in <i>ovector</i>, which is negative for unset +substrings. +</P> +<P> +The two convenience functions <b>pcre_free_substring()</b> and +<b>pcre_free_substring_list()</b> can be used to free the memory returned by +a previous call of <b>pcre_get_substring()</b> or +<b>pcre_get_substring_list()</b>, respectively. They do nothing more than call +the function pointed to by <b>pcre_free</b>, which of course could be called +directly from a C program. However, PCRE is used in some situations where it is +linked via a special interface to another programming language which cannot use +<b>pcre_free</b> directly; it is for these cases that the functions are +provided. +</P> +<br><a name="SEC12" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> +<P> +<b>int pcre_copy_named_substring(const pcre *<i>code</i>,</b> +<b>const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b>char *<i>buffer</i>, int <i>buffersize</i>);</b> +</P> +<P> +<b>int pcre_get_stringnumber(const pcre *<i>code</i>,</b> +<b>const char *<i>name</i>);</b> +</P> +<P> +<b>int pcre_get_named_substring(const pcre *<i>code</i>,</b> +<b>const char *<i>subject</i>, int *<i>ovector</i>,</b> +<b>int <i>stringcount</i>, const char *<i>stringname</i>,</b> +<b>const char **<i>stringptr</i>);</b> +</P> +<P> +To extract a substring by name, you first have to find associated number. This +can be done by calling <b>pcre_get_stringnumber()</b>. The first argument is the +compiled pattern, and the second is the name. For example, for this pattern +</P> +<P> +<pre> + ab(?<xxx>\d+)... +</PRE> +</P> +<P> +the number of the subpattern called "xxx" is 1. Given the number, you can then +extract the substring directly, or use one of the functions described in the +previous section. For convenience, there are also two functions that do the +whole job. +</P> +<P> +Most of the arguments of <i>pcre_copy_named_substring()</i> and +<i>pcre_get_named_substring()</i> are the same as those for the functions that +extract by number, and so are not re-described here. There are just two +differences. +</P> +<P> +First, instead of a substring number, a substring name is given. Second, there +is an extra argument, given at the start, which is a pointer to the compiled +pattern. This is needed in order to gain access to the name-to-number +translation table. +</P> +<P> +These functions call <b>pcre_get_stringnumber()</b>, and if it succeeds, they +then call <i>pcre_copy_substring()</i> or <i>pcre_get_substring()</i>, as +appropriate. +</P> +<P> +Last updated: 09 December 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcrebuild.html b/external-libs/pcre/doc/html/pcrebuild.html new file mode 100644 index 00000000..c70f8221 --- /dev/null +++ b/external-libs/pcre/doc/html/pcrebuild.html @@ -0,0 +1,189 @@ +<html> +<head> +<title>pcrebuild specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a> +<li><a name="TOC2" href="#SEC2">UTF-8 SUPPORT</a> +<li><a name="TOC3" href="#SEC3">CODE VALUE OF NEWLINE</a> +<li><a name="TOC4" href="#SEC4">BUILDING SHARED AND STATIC LIBRARIES</a> +<li><a name="TOC5" href="#SEC5">POSIX MALLOC USAGE</a> +<li><a name="TOC6" href="#SEC6">LIMITING PCRE RESOURCE USAGE</a> +<li><a name="TOC7" href="#SEC7">HANDLING VERY LARGE PATTERNS</a> +<li><a name="TOC8" href="#SEC8">AVOIDING EXCESSIVE STACK USAGE</a> +<li><a name="TOC9" href="#SEC9">USING EBCDIC CODE</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br> +<P> +This document describes the optional features of PCRE that can be selected when +the library is compiled. They are all selected, or deselected, by providing +options to the <b>configure</b> script which is run before the <b>make</b> +command. The complete list of options for <b>configure</b> (which includes the +standard ones such as the selection of the installation directory) can be +obtained by running +</P> +<P> +<pre> + ./configure --help +</PRE> +</P> +<P> +The following sections describe certain options whose names begin with --enable +or --disable. These settings specify changes to the defaults for the +<b>configure</b> command. Because of the way that <b>configure</b> works, +--enable and --disable always come in pairs, so the complementary option always +exists as well, but as it specifies the default, it is not described. +</P> +<br><a name="SEC2" href="#TOC1">UTF-8 SUPPORT</a><br> +<P> +To build PCRE with support for UTF-8 character strings, add +</P> +<P> +<pre> + --enable-utf8 +</PRE> +</P> +<P> +to the <b>configure</b> command. Of itself, this does not make PCRE treat +strings as UTF-8. As well as compiling PCRE with this option, you also have +have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b> +function. +</P> +<br><a name="SEC3" href="#TOC1">CODE VALUE OF NEWLINE</a><br> +<P> +By default, PCRE treats character 10 (linefeed) as the newline character. This +is the normal newline character on Unix-like systems. You can compile PCRE to +use character 13 (carriage return) instead by adding +</P> +<P> +<pre> + --enable-newline-is-cr +</PRE> +</P> +<P> +to the <b>configure</b> command. For completeness there is also a +--enable-newline-is-lf option, which explicitly specifies linefeed as the +newline character. +</P> +<br><a name="SEC4" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br> +<P> +The PCRE building process uses <b>libtool</b> to build both shared and static +Unix libraries by default. You can suppress one of these by adding one of +</P> +<P> +<pre> + --disable-shared + --disable-static +</PRE> +</P> +<P> +to the <b>configure</b> command, as required. +</P> +<br><a name="SEC5" href="#TOC1">POSIX MALLOC USAGE</a><br> +<P> +When PCRE is called through the POSIX interface (see the <b>pcreposix</b> +documentation), additional working storage is required for holding the pointers +to capturing substrings because PCRE requires three integers per substring, +whereas the POSIX interface provides only two. If the number of expected +substrings is small, the wrapper function uses space on the stack, because this +is faster than using <b>malloc()</b> for each call. The default threshold above +which the stack is no longer used is 10; it can be changed by adding a setting +such as +</P> +<P> +<pre> + --with-posix-malloc-threshold=20 +</PRE> +</P> +<P> +to the <b>configure</b> command. +</P> +<br><a name="SEC6" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br> +<P> +Internally, PCRE has a function called <b>match()</b> which it calls repeatedly +(possibly recursively) when performing a matching operation. By limiting the +number of times this function may be called, a limit can be placed on the +resources used by a single call to <b>pcre_exec()</b>. The limit can be changed +at run time, as described in the <b>pcreapi</b> documentation. The default is 10 +million, but this can be changed by adding a setting such as +</P> +<P> +<pre> + --with-match-limit=500000 +</PRE> +</P> +<P> +to the <b>configure</b> command. +</P> +<br><a name="SEC7" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br> +<P> +Within a compiled pattern, offset values are used to point from one part to +another (for example, from an opening parenthesis to an alternation +metacharacter). By default two-byte values are used for these offsets, leading +to a maximum size for a compiled pattern of around 64K. This is sufficient to +handle all but the most gigantic patterns. Nevertheless, some people do want to +process enormous patterns, so it is possible to compile PCRE to use three-byte +or four-byte offsets by adding a setting such as +</P> +<P> +<pre> + --with-link-size=3 +</PRE> +</P> +<P> +to the <b>configure</b> command. The value given must be 2, 3, or 4. Using +longer offsets slows down the operation of PCRE because it has to load +additional bytes when handling them. +</P> +<P> +If you build PCRE with an increased link size, test 2 (and test 5 if you are +using UTF-8) will fail. Part of the output of these tests is a representation +of the compiled pattern, and this changes with the link size. +</P> +<br><a name="SEC8" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br> +<P> +PCRE implements backtracking while matching by making recursive calls to an +internal function called <b>match()</b>. In environments where the size of the +stack is limited, this can severely limit PCRE's operation. (The Unix +environment does not usually suffer from this problem.) An alternative approach +that uses memory from the heap to remember data, instead of using recursive +function calls, has been implemented to work round this problem. If you want to +build a version of PCRE that works this way, add +</P> +<P> +<pre> + --disable-stack-for-recursion +</PRE> +</P> +<P> +to the <b>configure</b> command. With this configuration, PCRE will use the +<b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory +management functions. Separate functions are provided because the usage is very +predictable: the block sizes requested are always the same, and the blocks are +always freed in reverse order. A calling program might be able to implement +optimized functions that perform better than the standard <b>malloc()</b> and +<b>free()</b> functions. PCRE runs noticeably more slowly when built in this +way. +</P> +<br><a name="SEC9" href="#TOC1">USING EBCDIC CODE</a><br> +<P> +PCRE assumes by default that it will run in an environment where the character +code is ASCII (or UTF-8, which is a superset of ASCII). PCRE can, however, be +compiled to run in an EBCDIC environment by adding +</P> +<P> +<pre> + --enable-ebcdic +</PRE> +</P> +<P> +to the <b>configure</b> command. +</P> +<P> +Last updated: 09 December 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcrecallout.html b/external-libs/pcre/doc/html/pcrecallout.html new file mode 100644 index 00000000..f4b7104e --- /dev/null +++ b/external-libs/pcre/doc/html/pcrecallout.html @@ -0,0 +1,117 @@ +<html> +<head> +<title>pcrecallout specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE CALLOUTS</a> +<li><a name="TOC2" href="#SEC2">RETURN VALUES</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE CALLOUTS</a><br> +<P> +<b>int (*pcre_callout)(pcre_callout_block *);</b> +</P> +<P> +PCRE provides a feature called "callout", which is a means of temporarily +passing control to the caller of PCRE in the middle of pattern matching. The +caller of PCRE provides an external function by putting its entry point in the +global variable <i>pcre_callout</i>. By default, this variable contains NULL, +which disables all calling out. +</P> +<P> +Within a regular expression, (?C) indicates the points at which the external +function is to be called. Different callout points can be identified by putting +a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: +</P> +<P> +<pre> + (?C1)\dabc(?C2)def +</PRE> +</P> +<P> +During matching, when PCRE reaches a callout point (and <i>pcre_callout</i> is +set), the external function is called. Its only argument is a pointer to a +<b>pcre_callout</b> block. This contains the following variables: +</P> +<P> +<pre> + int <i>version</i>; + int <i>callout_number</i>; + int *<i>offset_vector</i>; + const char *<i>subject</i>; + int <i>subject_length</i>; + int <i>start_match</i>; + int <i>current_position</i>; + int <i>capture_top</i>; + int <i>capture_last</i>; + void *<i>callout_data</i>; +</PRE> +</P> +<P> +The <i>version</i> field is an integer containing the version number of the +block format. The current version is zero. The version number may change in +future if additional fields are added, but the intention is never to remove any +of the existing fields. +</P> +<P> +The <i>callout_number</i> field contains the number of the callout, as compiled +into the pattern (that is, the number after ?C). +</P> +<P> +The <i>offset_vector</i> field is a pointer to the vector of offsets that was +passed by the caller to <b>pcre_exec()</b>. The contents can be inspected in +order to extract substrings that have been matched so far, in the same way as +for extracting substrings after a match has completed. +</P> +<P> +The <i>subject</i> and <i>subject_length</i> fields contain copies the values +that were passed to <b>pcre_exec()</b>. +</P> +<P> +The <i>start_match</i> field contains the offset within the subject at which the +current match attempt started. If the pattern is not anchored, the callout +function may be called several times for different starting points. +</P> +<P> +The <i>current_position</i> field contains the offset within the subject of the +current match pointer. +</P> +<P> +The <i>capture_top</i> field contains one more than the number of the highest +numbered captured substring so far. If no substrings have been captured, +the value of <i>capture_top</i> is one. +</P> +<P> +The <i>capture_last</i> field contains the number of the most recently captured +substring. +</P> +<P> +The <i>callout_data</i> field contains a value that is passed to +<b>pcre_exec()</b> by the caller specifically so that it can be passed back in +callouts. It is passed in the <i>pcre_callout</i> field of the <b>pcre_extra</b> +data structure. If no such data was passed, the value of <i>callout_data</i> in +a <b>pcre_callout</b> block is NULL. There is a description of the +<b>pcre_extra</b> structure in the <b>pcreapi</b> documentation. +</P> +<br><a name="SEC2" href="#TOC1">RETURN VALUES</a><br> +<P> +The callout function returns an integer. If the value is zero, matching +proceeds as normal. If the value is greater than zero, matching fails at the +current point, but backtracking to test other possibilities goes ahead, just as +if a lookahead assertion had failed. If the value is less than zero, the match +is abandoned, and <b>pcre_exec()</b> returns the value. +</P> +<P> +Negative values should normally be chosen from the set of PCRE_ERROR_xxx +values. In particular, PCRE_ERROR_NOMATCH forces a standard "no match" failure. +The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; +it will never be used by PCRE itself. +</P> +<P> +Last updated: 21 January 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcrecompat.html b/external-libs/pcre/doc/html/pcrecompat.html new file mode 100644 index 00000000..1ec22038 --- /dev/null +++ b/external-libs/pcre/doc/html/pcrecompat.html @@ -0,0 +1,136 @@ +<html> +<head> +<title>pcrecompat specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">DIFFERENCES FROM PERL</a> +</ul> +<br><a name="SEC1" href="#TOC1">DIFFERENCES FROM PERL</a><br> +<P> +This document describes the differences in the ways that PCRE and Perl handle +regular expressions. The differences described here are with respect to Perl +5.8. +</P> +<P> +1. PCRE does not have full UTF-8 support. Details of what it does have are +given in the +<a href="pcre.html#utf8support">section on UTF-8 support</a> +in the main +<a href="pcre.html"><b>pcre</b></a> +page. +</P> +<P> +2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl permits +them, but they do not mean what you might think. For example, (?!a){3} does +not assert that the next three characters are not "a". It just asserts that the +next character is not "a" three times. +</P> +<P> +3. Capturing subpatterns that occur inside negative lookahead assertions are +counted, but their entries in the offsets vector are never set. Perl sets its +numerical variables from any such patterns that are matched before the +assertion fails to match something (thereby succeeding), but only if the +negative lookahead assertion contains just one branch. +</P> +<P> +4. Though binary zero characters are supported in the subject string, they are +not allowed in a pattern string because it is passed as a normal C string, +terminated by zero. The escape sequence "\0" can be used in the pattern to +represent a binary zero. +</P> +<P> +5. The following Perl escape sequences are not supported: \l, \u, \L, +\U, \P, \p, \N, and \X. In fact these are implemented by Perl's general +string-handling and are not part of its pattern matching engine. If any of +these are encountered by PCRE, an error is generated. +</P> +<P> +6. PCRE does support the \Q...\E escape for quoting substrings. Characters in +between are treated as literals. This is slightly different from Perl in that $ +and @ are also handled as literals inside the quotes. In Perl, they cause +variable interpolation (but of course PCRE does not have variables). Note the +following examples: +</P> +<P> +<pre> + Pattern PCRE matches Perl matches +</PRE> +</P> +<P> +<pre> + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz +</PRE> +</P> +<P> +The \Q...\E sequence is recognized both inside and outside character classes. +</P> +<P> +7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) +constructions. However, there is some experimental support for recursive +patterns using the non-Perl items (?R), (?number) and (?P>name). Also, the PCRE +"callout" feature allows an external function to be called during pattern +matching. +</P> +<P> +8. There are some differences that are concerned with the settings of captured +strings when part of a pattern is repeated. For example, matching "aba" against +the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b". +</P> +<P> +9. PCRE provides some extensions to the Perl regular expression facilities: +</P> +<P> +(a) Although lookbehind assertions must match fixed length strings, each +alternative branch of a lookbehind assertion can match a different length of +string. Perl requires them all to have the same length. +</P> +<P> +(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ +meta-character matches only at the very end of the string. +</P> +<P> +© If PCRE_EXTRA is set, a backslash followed by a letter with no special +meaning is faulted. +</P> +<P> +(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is +inverted, that is, by default they are not greedy, but if followed by a +question mark they are. +</P> +<P> +(e) PCRE_ANCHORED can be used to force a pattern to be tried only at the first +matching position in the subject string. +</P> +<P> +(f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAPTURE +options for <b>pcre_exec()</b> have no Perl equivalents. +</P> +<P> +(g) The (?R), (?number), and (?P>name) constructs allows for recursive pattern +matching (Perl can do this using the (?p{code}) construct, which PCRE cannot +support.) +</P> +<P> +(h) PCRE supports named capturing substrings, using the Python syntax. +</P> +<P> +(i) PCRE supports the possessive quantifier "++" syntax, taken from Sun's Java +package. +</P> +<P> +(j) The (R) condition, for testing recursion, is a PCRE extension. +</P> +<P> +(k) The callout facility is PCRE-specific. +</P> +<P> +Last updated: 09 December 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcregrep.html b/external-libs/pcre/doc/html/pcregrep.html new file mode 100644 index 00000000..a76cac21 --- /dev/null +++ b/external-libs/pcre/doc/html/pcregrep.html @@ -0,0 +1,153 @@ +<html> +<head> +<title>pcregrep specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">OPTIONS</a> +<li><a name="TOC4" href="#SEC4">LONG OPTIONS</a> +<li><a name="TOC5" href="#SEC5">DIAGNOSTICS</a> +<li><a name="TOC6" href="#SEC6">AUTHOR</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>pcregrep [-Vcfhilnrsuvx] [long options] [pattern] [file1 file2 ...]</b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +<b>pcregrep</b> searches files for character patterns, in the same way as other +grep commands do, but it uses the PCRE regular expression library to support +patterns that are compatible with the regular expressions of Perl 5. See +<a href="pcrepattern.html"><b>pcrepattern</b></a> +for a full description of syntax and semantics of the regular expressions that +PCRE supports. +</P> +<P> +A pattern must be specified on the command line unless the <b>-f</b> option is +used (see below). +</P> +<P> +If no files are specified, <b>pcregrep</b> reads the standard input. By default, +each line that matches the pattern is copied to the standard output, and if +there is more than one file, the file name is printed before each line of +output. However, there are options that can change how <b>pcregrep</b> behaves. +</P> +<P> +Lines are limited to BUFSIZ characters. BUFSIZ is defined in <b><stdio.h></b>. +The newline character is removed from the end of each line before it is matched +against the pattern. +</P> +<br><a name="SEC3" href="#TOC1">OPTIONS</a><br> +<P> +<b>-V</b> +Write the version number of the PCRE library being used to the standard error +stream. +</P> +<P> +<b>-c</b> +Do not print individual lines; instead just print a count of the number of +lines that would otherwise have been printed. If several files are given, a +count is printed for each of them. +</P> +<P> +<b>-f</b><i>filename</i> +Read a number of patterns from the file, one per line, and match all of them +against each line of input. A line is output if any of the patterns match it. +When <b>-f</b> is used, no pattern is taken from the command line; all arguments +are treated as file names. There is a maximum of 100 patterns. Trailing white +space is removed, and blank lines are ignored. An empty file contains no +patterns and therefore matches nothing. +</P> +<P> +<b>-h</b> +Suppress printing of filenames when searching multiple files. +</P> +<P> +<b>-i</b> +Ignore upper/lower case distinctions during comparisons. +</P> +<P> +<b>-l</b> +Instead of printing lines from the files, just print the names of the files +containing lines that would have been printed. Each file name is printed +once, on a separate line. +</P> +<P> +<b>-n</b> +Precede each line by its line number in the file. +</P> +<P> +<b>-r</b> +If any file is a directory, recursively scan the files it contains. Without +<b>-r</b> a directory is scanned as a normal file. +</P> +<P> +<b>-s</b> +Work silently, that is, display nothing except error messages. +The exit status indicates whether any matches were found. +</P> +<P> +<b>-u</b> +Operate in UTF-8 mode. This option is available only if PCRE has been compiled +with UTF-8 support. Both the pattern and each subject line are assumed to be +valid strings of UTF-8 characters. +</P> +<P> +<b>-v</b> +Invert the sense of the match, so that lines which do <i>not</i> match the +pattern are now the ones that are found. +</P> +<P> +<b>-x</b> +Force the pattern to be anchored (it must start matching at the beginning of +the line) and in addition, require it to match the entire line. This is +equivalent to having ^ and $ characters at the start and end of each +alternative branch in the regular expression. +</P> +<br><a name="SEC4" href="#TOC1">LONG OPTIONS</a><br> +<P> +Long forms of all the options are available, as in GNU grep. They are shown in +the following table: +</P> +<P> +<pre> + -c --count + -h --no-filename + -i --ignore-case + -l --files-with-matches + -n --line-number + -r --recursive + -s --no-messages + -u --utf-8 + -V --version + -v --invert-match + -x --line-regex + -x --line-regexp +</PRE> +</P> +<P> +In addition, --file=<i>filename</i> is equivalent to -f<i>filename</i>, and +--help shows the list of options and then exits. +</P> +<br><a name="SEC5" href="#TOC1">DIAGNOSTICS</a><br> +<P> +Exit status is 0 if any matches were found, 1 if no matches were found, and 2 +for syntax errors or inacessible files (even if matches were found). +</P> +<br><a name="SEC6" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel <ph10@cam.ac.uk> +<br> +University Computing Service +<br> +Cambridge CB2 3QG, England. +</P> +<P> +Last updated: 03 February 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcrepattern.html b/external-libs/pcre/doc/html/pcrepattern.html new file mode 100644 index 00000000..65abcc21 --- /dev/null +++ b/external-libs/pcre/doc/html/pcrepattern.html @@ -0,0 +1,1607 @@ +<html> +<head> +<title>pcrepattern specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE REGULAR EXPRESSION DETAILS</a> +<li><a name="TOC2" href="#SEC2">BACKSLASH</a> +<li><a name="TOC3" href="#SEC3">CIRCUMFLEX AND DOLLAR</a> +<li><a name="TOC4" href="#SEC4">FULL STOP (PERIOD, DOT)</a> +<li><a name="TOC5" href="#SEC5">MATCHING A SINGLE BYTE</a> +<li><a name="TOC6" href="#SEC6">SQUARE BRACKETS</a> +<li><a name="TOC7" href="#SEC7">POSIX CHARACTER CLASSES</a> +<li><a name="TOC8" href="#SEC8">VERTICAL BAR</a> +<li><a name="TOC9" href="#SEC9">INTERNAL OPTION SETTING</a> +<li><a name="TOC10" href="#SEC10">SUBPATTERNS</a> +<li><a name="TOC11" href="#SEC11">NAMED SUBPATTERNS</a> +<li><a name="TOC12" href="#SEC12">REPETITION</a> +<li><a name="TOC13" href="#SEC13">ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS</a> +<li><a name="TOC14" href="#SEC14">BACK REFERENCES</a> +<li><a name="TOC15" href="#SEC15">ASSERTIONS</a> +<li><a name="TOC16" href="#SEC16">CONDITIONAL SUBPATTERNS</a> +<li><a name="TOC17" href="#SEC17">COMMENTS</a> +<li><a name="TOC18" href="#SEC18">RECURSIVE PATTERNS</a> +<li><a name="TOC19" href="#SEC19">SUBPATTERNS AS SUBROUTINES</a> +<li><a name="TOC20" href="#SEC20">CALLOUTS</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION DETAILS</a><br> +<P> +The syntax and semantics of the regular expressions supported by PCRE are +described below. Regular expressions are also described in the Perl +documentation and in a number of other books, some of which have copious +examples. Jeffrey Friedl's "Mastering Regular Expressions", published by +O'Reilly, covers them in great detail. The description here is intended as +reference documentation. +</P> +<P> +The basic operation of PCRE is on strings of bytes. However, there is also +support for UTF-8 character strings. To use this support you must build PCRE to +include UTF-8 support, and then call <b>pcre_compile()</b> with the PCRE_UTF8 +option. How this affects the pattern matching is mentioned in several places +below. There is also a summary of UTF-8 features in the +<a href="pcre.html#utf8support">section on UTF-8 support</a> +in the main +<a href="pcre.html"><b>pcre</b></a> +page. +</P> +<P> +A regular expression is a pattern that is matched against a subject string from +left to right. Most characters stand for themselves in a pattern, and match the +corresponding characters in the subject. As a trivial example, the pattern +</P> +<P> +<pre> + The quick brown fox +</PRE> +</P> +<P> +matches a portion of a subject string that is identical to itself. The power of +regular expressions comes from the ability to include alternatives and +repetitions in the pattern. These are encoded in the pattern by the use of +<i>meta-characters</i>, which do not stand for themselves but instead are +interpreted in some special way. +</P> +<P> +There are two different sets of meta-characters: those that are recognized +anywhere in the pattern except within square brackets, and those that are +recognized in square brackets. Outside square brackets, the meta-characters are +as follows: +</P> +<P> +<pre> + \ general escape character with several uses + ^ assert start of string (or line, in multiline mode) + $ assert end of string (or line, in multiline mode) + . match any character except newline (by default) + [ start character class definition + | start of alternative branch + ( start subpattern + ) end subpattern + ? extends the meaning of ( + also 0 or 1 quantifier + also quantifier minimizer + * 0 or more quantifier + + 1 or more quantifier + also "possessive quantifier" + { start min/max quantifier +</PRE> +</P> +<P> +Part of a pattern that is in square brackets is called a "character class". In +a character class the only meta-characters are: +</P> +<P> +<pre> + \ general escape character + ^ negate the class, but only if the first character + - indicates character range + [ POSIX character class (only if followed by POSIX + syntax) + ] terminates the character class +</PRE> +</P> +<P> +The following sections describe the use of each of the meta-characters. +</P> +<br><a name="SEC2" href="#TOC1">BACKSLASH</a><br> +<P> +The backslash character has several uses. Firstly, if it is followed by a +non-alphameric character, it takes away any special meaning that character may +have. This use of backslash as an escape character applies both inside and +outside character classes. +</P> +<P> +For example, if you want to match a * character, you write \* in the pattern. +This escaping action applies whether or not the following character would +otherwise be interpreted as a meta-character, so it is always safe to precede a +non-alphameric with backslash to specify that it stands for itself. In +particular, if you want to match a backslash, you write \\. +</P> +<P> +If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the +pattern (other than in a character class) and characters between a # outside +a character class and the next newline character are ignored. An escaping +backslash can be used to include a whitespace or # character as part of the +pattern. +</P> +<P> +If you want to remove the special meaning from a sequence of characters, you +can do so by putting them between \Q and \E. This is different from Perl in +that $ and @ are handled as literals in \Q...\E sequences in PCRE, whereas in +Perl, $ and @ cause variable interpolation. Note the following examples: +</P> +<P> +<pre> + Pattern PCRE matches Perl matches +</PRE> +</P> +<P> +<pre> + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz +</PRE> +</P> +<P> +The \Q...\E sequence is recognized both inside and outside character classes. +</P> +<P> +A second use of backslash provides a way of encoding non-printing characters +in patterns in a visible manner. There is no restriction on the appearance of +non-printing characters, apart from the binary zero that terminates a pattern, +but when a pattern is being prepared by text editing, it is usually easier to +use one of the following escape sequences than the binary character it +represents: +</P> +<P> +<pre> + \a alarm, that is, the BEL character (hex 07) + \cx "control-x", where x is any character + \e escape (hex 1B) + \f formfeed (hex 0C) + \n newline (hex 0A) + \r carriage return (hex 0D) + \t tab (hex 09) + \ddd character with octal code ddd, or backreference + \xhh character with hex code hh + \x{hhh..} character with hex code hhh... (UTF-8 mode only) +</PRE> +</P> +<P> +The precise effect of \cx is as follows: if x is a lower case letter, it +is converted to upper case. Then bit 6 of the character (hex 40) is inverted. +Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c; becomes hex +7B. +</P> +<P> +After \x, from zero to two hexadecimal digits are read (letters can be in +upper or lower case). In UTF-8 mode, any number of hexadecimal digits may +appear between \x{ and }, but the value of the character code must be less +than 2**31 (that is, the maximum hexadecimal value is 7FFFFFFF). If characters +other than hexadecimal digits appear between \x{ and }, or if there is no +terminating }, this form of escape is not recognized. Instead, the initial +\x will be interpreted as a basic hexadecimal escape, with no following +digits, giving a byte whose value is zero. +</P> +<P> +Characters whose value is less than 256 can be defined by either of the two +syntaxes for \x when PCRE is in UTF-8 mode. There is no difference in the +way they are handled. For example, \xdc is exactly the same as \x{dc}. +</P> +<P> +After \0 up to two further octal digits are read. In both cases, if there +are fewer than two digits, just those that are present are used. Thus the +sequence \0\x\07 specifies two binary zeros followed by a BEL character +(code value 7). Make sure you supply two digits after the initial zero if the +character that follows is itself an octal digit. +</P> +<P> +The handling of a backslash followed by a digit other than 0 is complicated. +Outside a character class, PCRE reads it and any following digits as a decimal +number. If the number is less than 10, or if there have been at least that many +previous capturing left parentheses in the expression, the entire sequence is +taken as a <i>back reference</i>. A description of how this works is given +later, following the discussion of parenthesized subpatterns. +</P> +<P> +Inside a character class, or if the decimal number is greater than 9 and there +have not been that many capturing subpatterns, PCRE re-reads up to three octal +digits following the backslash, and generates a single byte from the least +significant 8 bits of the value. Any subsequent digits stand for themselves. +For example: +</P> +<P> +<pre> + \040 is another way of writing a space + \40 is the same, provided there are fewer than 40 + previous capturing subpatterns + \7 is always a back reference + \11 might be a back reference, or another way of + writing a tab + \011 is always a tab + \0113 is a tab followed by the character "3" + \113 might be a back reference, otherwise the + character with octal code 113 + \377 might be a back reference, otherwise + the byte consisting entirely of 1 bits + \81 is either a back reference, or a binary zero + followed by the two characters "8" and "1" +</PRE> +</P> +<P> +Note that octal values of 100 or greater must not be introduced by a leading +zero, because no more than three octal digits are ever read. +</P> +<P> +All the sequences that define a single byte value or a single UTF-8 character +(in UTF-8 mode) can be used both inside and outside character classes. In +addition, inside a character class, the sequence \b is interpreted as the +backspace character (hex 08). Outside a character class it has a different +meaning (see below). +</P> +<P> +The third use of backslash is for specifying generic character types: +</P> +<P> +<pre> + \d any decimal digit + \D any character that is not a decimal digit + \s any whitespace character + \S any character that is not a whitespace character + \w any "word" character + \W any "non-word" character +</PRE> +</P> +<P> +Each pair of escape sequences partitions the complete set of characters into +two disjoint sets. Any given character matches one, and only one, of each pair. +</P> +<P> +In UTF-8 mode, characters with values greater than 255 never match \d, \s, or +\w, and always match \D, \S, and \W. +</P> +<P> +For compatibility with Perl, \s does not match the VT character (code 11). +This makes it different from the the POSIX "space" class. The \s characters +are HT (9), LF (10), FF (12), CR (13), and space (32). +</P> +<P> +A "word" character is any letter or digit or the underscore character, that is, +any character which can be part of a Perl "word". The definition of letters and +digits is controlled by PCRE's character tables, and may vary if locale- +specific matching is taking place (see +<a href="pcreapi.html#localesupport">"Locale support"</a> +in the +<a href="pcreapi.html"><b>pcreapi</b></a> +page). For example, in the "fr" (French) locale, some character codes greater +than 128 are used for accented letters, and these are matched by \w. +</P> +<P> +These character type sequences can appear both inside and outside character +classes. They each match one character of the appropriate type. If the current +matching point is at the end of the subject string, all of them fail, since +there is no character to match. +</P> +<P> +The fourth use of backslash is for certain simple assertions. An assertion +specifies a condition that has to be met at a particular point in a match, +without consuming any characters from the subject string. The use of +subpatterns for more complicated assertions is described below. The backslashed +assertions are +</P> +<P> +<pre> + \b matches at a word boundary + \B matches when not at a word boundary + \A matches at start of subject + \Z matches at end of subject or before newline at end + \z matches at end of subject + \G matches at first matching position in subject +</PRE> +</P> +<P> +These assertions may not appear in character classes (but note that \b has a +different meaning, namely the backspace character, inside a character class). +</P> +<P> +A word boundary is a position in the subject string where the current character +and the previous character do not both match \w or \W (i.e. one matches +\w and the other matches \W), or the start or end of the string if the +first or last character matches \w, respectively. +</P> +<P> +The \A, \Z, and \z assertions differ from the traditional circumflex and +dollar (described below) in that they only ever match at the very start and end +of the subject string, whatever options are set. Thus, they are independent of +multiline mode. +</P> +<P> +They are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options. If the +<i>startoffset</i> argument of <b>pcre_exec()</b> is non-zero, indicating that +matching is to start at a point other than the beginning of the subject, \A +can never match. The difference between \Z and \z is that \Z matches before +a newline that is the last character of the string as well as at the end of the +string, whereas \z matches only at the end. +</P> +<P> +The \G assertion is true only when the current matching position is at the +start point of the match, as specified by the <i>startoffset</i> argument of +<b>pcre_exec()</b>. It differs from \A when the value of <i>startoffset</i> is +non-zero. By calling <b>pcre_exec()</b> multiple times with appropriate +arguments, you can mimic Perl's /g option, and it is in this kind of +implementation where \G can be useful. +</P> +<P> +Note, however, that PCRE's interpretation of \G, as the start of the current +match, is subtly different from Perl's, which defines it as the end of the +previous match. In Perl, these can be different when the previously matched +string was empty. Because PCRE does just one match at a time, it cannot +reproduce this behaviour. +</P> +<P> +If all the alternatives of a pattern begin with \G, the expression is anchored +to the starting match position, and the "anchored" flag is set in the compiled +regular expression. +</P> +<br><a name="SEC3" href="#TOC1">CIRCUMFLEX AND DOLLAR</a><br> +<P> +Outside a character class, in the default matching mode, the circumflex +character is an assertion which is true only if the current matching point is +at the start of the subject string. If the <i>startoffset</i> argument of +<b>pcre_exec()</b> is non-zero, circumflex can never match if the PCRE_MULTILINE +option is unset. Inside a character class, circumflex has an entirely different +meaning (see below). +</P> +<P> +Circumflex need not be the first character of the pattern if a number of +alternatives are involved, but it should be the first thing in each alternative +in which it appears if the pattern is ever to match that branch. If all +possible alternatives start with a circumflex, that is, if the pattern is +constrained to match only at the start of the subject, it is said to be an +"anchored" pattern. (There are also other constructs that can cause a pattern +to be anchored.) +</P> +<P> +A dollar character is an assertion which is true only if the current matching +point is at the end of the subject string, or immediately before a newline +character that is the last character in the string (by default). Dollar need +not be the last character of the pattern if a number of alternatives are +involved, but it should be the last item in any branch in which it appears. +Dollar has no special meaning in a character class. +</P> +<P> +The meaning of dollar can be changed so that it matches only at the very end of +the string, by setting the PCRE_DOLLAR_ENDONLY option at compile time. This +does not affect the \Z assertion. +</P> +<P> +The meanings of the circumflex and dollar characters are changed if the +PCRE_MULTILINE option is set. When this is the case, they match immediately +after and immediately before an internal newline character, respectively, in +addition to matching at the start and end of the subject string. For example, +the pattern /^abc$/ matches the subject string "def\nabc" in multiline mode, +but not otherwise. Consequently, patterns that are anchored in single line mode +because all branches start with ^ are not anchored in multiline mode, and a +match for circumflex is possible when the <i>startoffset</i> argument of +<b>pcre_exec()</b> is non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if +PCRE_MULTILINE is set. +</P> +<P> +Note that the sequences \A, \Z, and \z can be used to match the start and +end of the subject in both modes, and if all branches of a pattern start with +\A it is always anchored, whether PCRE_MULTILINE is set or not. +</P> +<br><a name="SEC4" href="#TOC1">FULL STOP (PERIOD, DOT)</a><br> +<P> +Outside a character class, a dot in the pattern matches any one character in +the subject, including a non-printing character, but not (by default) newline. +In UTF-8 mode, a dot matches any UTF-8 character, which might be more than one +byte long, except (by default) for newline. If the PCRE_DOTALL option is set, +dots match newlines as well. The handling of dot is entirely independent of the +handling of circumflex and dollar, the only relationship being that they both +involve newline characters. Dot has no special meaning in a character class. +</P> +<br><a name="SEC5" href="#TOC1">MATCHING A SINGLE BYTE</a><br> +<P> +Outside a character class, the escape sequence \C matches any one byte, both +in and out of UTF-8 mode. Unlike a dot, it always matches a newline. The +feature is provided in Perl in order to match individual bytes in UTF-8 mode. +Because it breaks up UTF-8 characters into individual bytes, what remains in +the string may be a malformed UTF-8 string. For this reason it is best avoided. +</P> +<P> +PCRE does not allow \C to appear in lookbehind assertions (see below), because +in UTF-8 mode it makes it impossible to calculate the length of the lookbehind. +</P> +<br><a name="SEC6" href="#TOC1">SQUARE BRACKETS</a><br> +<P> +An opening square bracket introduces a character class, terminated by a closing +square bracket. A closing square bracket on its own is not special. If a +closing square bracket is required as a member of the class, it should be the +first data character in the class (after an initial circumflex, if present) or +escaped with a backslash. +</P> +<P> +A character class matches a single character in the subject. In UTF-8 mode, the +character may occupy more than one byte. A matched character must be in the set +of characters defined by the class, unless the first character in the class +definition is a circumflex, in which case the subject character must not be in +the set defined by the class. If a circumflex is actually required as a member +of the class, ensure it is not the first character, or escape it with a +backslash. +</P> +<P> +For example, the character class [aeiou] matches any lower case vowel, while +[^aeiou] matches any character that is not a lower case vowel. Note that a +circumflex is just a convenient notation for specifying the characters which +are in the class by enumerating those that are not. It is not an assertion: it +still consumes a character from the subject string, and fails if the current +pointer is at the end of the string. +</P> +<P> +In UTF-8 mode, characters with values greater than 255 can be included in a +class as a literal string of bytes, or by using the \x{ escaping mechanism. +</P> +<P> +When caseless matching is set, any letters in a class represent both their +upper case and lower case versions, so for example, a caseless [aeiou] matches +"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a +caseful version would. PCRE does not support the concept of case for characters +with values greater than 255. +</P> +<P> +The newline character is never treated in any special way in character classes, +whatever the setting of the PCRE_DOTALL or PCRE_MULTILINE options is. A class +such as [^a] will always match a newline. +</P> +<P> +The minus (hyphen) character can be used to specify a range of characters in a +character class. For example, [d-m] matches any letter between d and m, +inclusive. If a minus character is required in a class, it must be escaped with +a backslash or appear in a position where it cannot be interpreted as +indicating a range, typically as the first or last character in the class. +</P> +<P> +It is not possible to have the literal character "]" as the end character of a +range. A pattern such as [W-]46] is interpreted as a class of two characters +("W" and "-") followed by a literal string "46]", so it would match "W46]" or +"-46]". However, if the "]" is escaped with a backslash it is interpreted as +the end of range, so [W-\]46] is interpreted as a single class containing a +range followed by two separate characters. The octal or hexadecimal +representation of "]" can also be used to end a range. +</P> +<P> +Ranges operate in the collating sequence of character values. They can also be +used for characters specified numerically, for example [\000-\037]. In UTF-8 +mode, ranges can include characters whose values are greater than 255, for +example [\x{100}-\x{2ff}]. +</P> +<P> +If a range that includes letters is used when caseless matching is set, it +matches the letters in either case. For example, [W-c] is equivalent to +[][\^_`wxyzabc], matched caselessly, and if character tables for the "fr" +locale are in use, [\xc8-\xcb] matches accented E characters in both cases. +</P> +<P> +The character types \d, \D, \s, \S, \w, and \W may also appear in a +character class, and add the characters that they match to the class. For +example, [\dABCDEF] matches any hexadecimal digit. A circumflex can +conveniently be used with the upper case character types to specify a more +restricted set of characters than the matching lower case type. For example, +the class [^\W_] matches any letter or digit, but not underscore. +</P> +<P> +All non-alphameric characters other than \, -, ^ (at the start) and the +terminating ] are non-special in character classes, but it does no harm if they +are escaped. +</P> +<br><a name="SEC7" href="#TOC1">POSIX CHARACTER CLASSES</a><br> +<P> +Perl supports the POSIX notation for character classes, which uses names +enclosed by [: and :] within the enclosing square brackets. PCRE also supports +this notation. For example, +</P> +<P> +<pre> + [01[:alpha:]%] +</PRE> +</P> +<P> +matches "0", "1", any alphabetic character, or "%". The supported class names +are +</P> +<P> +<pre> + alnum letters and digits + alpha letters + ascii character codes 0 - 127 + blank space or tab only + cntrl control characters + digit decimal digits (same as \d) + graph printing characters, excluding space + lower lower case letters + print printing characters, including space + punct printing characters, excluding letters and digits + space white space (not quite the same as \s) + upper upper case letters + word "word" characters (same as \w) + xdigit hexadecimal digits +</PRE> +</P> +<P> +The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), and +space (32). Notice that this list includes the VT character (code 11). This +makes "space" different to \s, which does not include VT (for Perl +compatibility). +</P> +<P> +The name "word" is a Perl extension, and "blank" is a GNU extension from Perl +5.8. Another Perl extension is negation, which is indicated by a ^ character +after the colon. For example, +</P> +<P> +<pre> + [12[:^digit:]] +</PRE> +</P> +<P> +matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the POSIX +syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not +supported, and an error is given if they are encountered. +</P> +<P> +In UTF-8 mode, characters with values greater than 255 do not match any of +the POSIX character classes. +</P> +<br><a name="SEC8" href="#TOC1">VERTICAL BAR</a><br> +<P> +Vertical bar characters are used to separate alternative patterns. For example, +the pattern +</P> +<P> +<pre> + gilbert|sullivan +</PRE> +</P> +<P> +matches either "gilbert" or "sullivan". Any number of alternatives may appear, +and an empty alternative is permitted (matching the empty string). +The matching process tries each alternative in turn, from left to right, +and the first one that succeeds is used. If the alternatives are within a +subpattern (defined below), "succeeds" means matching the rest of the main +pattern as well as the alternative in the subpattern. +</P> +<br><a name="SEC9" href="#TOC1">INTERNAL OPTION SETTING</a><br> +<P> +The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and +PCRE_EXTENDED options can be changed from within the pattern by a sequence of +Perl option letters enclosed between "(?" and ")". The option letters are +</P> +<P> +<pre> + i for PCRE_CASELESS + m for PCRE_MULTILINE + s for PCRE_DOTALL + x for PCRE_EXTENDED +</PRE> +</P> +<P> +For example, (?im) sets caseless, multiline matching. It is also possible to +unset these options by preceding the letter with a hyphen, and a combined +setting and unsetting such as (?im-sx), which sets PCRE_CASELESS and +PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, is also +permitted. If a letter appears both before and after the hyphen, the option is +unset. +</P> +<P> +When an option change occurs at top level (that is, not inside subpattern +parentheses), the change applies to the remainder of the pattern that follows. +If the change is placed right at the start of a pattern, PCRE extracts it into +the global options (and it will therefore show up in data extracted by the +<b>pcre_fullinfo()</b> function). +</P> +<P> +An option change within a subpattern affects only that part of the current +pattern that follows it, so +</P> +<P> +<pre> + (a(?i)b)c +</PRE> +</P> +<P> +matches abc and aBc and no other strings (assuming PCRE_CASELESS is not used). +By this means, options can be made to have different settings in different +parts of the pattern. Any changes made in one alternative do carry on +into subsequent branches within the same subpattern. For example, +</P> +<P> +<pre> + (a(?i)b|c) +</PRE> +</P> +<P> +matches "ab", "aB", "c", and "C", even though when matching "C" the first +branch is abandoned before the option setting. This is because the effects of +option settings happen at compile time. There would be some very weird +behaviour otherwise. +</P> +<P> +The PCRE-specific options PCRE_UNGREEDY and PCRE_EXTRA can be changed in the +same way as the Perl-compatible options by using the characters U and X +respectively. The (?X) flag setting is special in that it must always occur +earlier in the pattern than any of the additional features it turns on, even +when it is at top level. It is best put at the start. +</P> +<br><a name="SEC10" href="#TOC1">SUBPATTERNS</a><br> +<P> +Subpatterns are delimited by parentheses (round brackets), which can be nested. +Marking part of a pattern as a subpattern does two things: +</P> +<P> +1. It localizes a set of alternatives. For example, the pattern +</P> +<P> +<pre> + cat(aract|erpillar|) +</PRE> +</P> +<P> +matches one of the words "cat", "cataract", or "caterpillar". Without the +parentheses, it would match "cataract", "erpillar" or the empty string. +</P> +<P> +2. It sets up the subpattern as a capturing subpattern (as defined above). +When the whole pattern matches, that portion of the subject string that matched +the subpattern is passed back to the caller via the <i>ovector</i> argument of +<b>pcre_exec()</b>. Opening parentheses are counted from left to right (starting +from 1) to obtain the numbers of the capturing subpatterns. +</P> +<P> +For example, if the string "the red king" is matched against the pattern +</P> +<P> +<pre> + the ((red|white) (king|queen)) +</PRE> +</P> +<P> +the captured substrings are "red king", "red", and "king", and are numbered 1, +2, and 3, respectively. +</P> +<P> +The fact that plain parentheses fulfil two functions is not always helpful. +There are often times when a grouping subpattern is required without a +capturing requirement. If an opening parenthesis is followed by a question mark +and a colon, the subpattern does not do any capturing, and is not counted when +computing the number of any subsequent capturing subpatterns. For example, if +the string "the white queen" is matched against the pattern +</P> +<P> +<pre> + the ((?:red|white) (king|queen)) +</PRE> +</P> +<P> +the captured substrings are "white queen" and "queen", and are numbered 1 and +2. The maximum number of capturing subpatterns is 65535, and the maximum depth +of nesting of all subpatterns, both capturing and non-capturing, is 200. +</P> +<P> +As a convenient shorthand, if any option settings are required at the start of +a non-capturing subpattern, the option letters may appear between the "?" and +the ":". Thus the two patterns +</P> +<P> +<pre> + (?i:saturday|sunday) + (?:(?i)saturday|sunday) +</PRE> +</P> +<P> +match exactly the same set of strings. Because alternative branches are tried +from left to right, and options are not reset until the end of the subpattern +is reached, an option setting in one branch does affect subsequent branches, so +the above patterns match "SUNDAY" as well as "Saturday". +</P> +<br><a name="SEC11" href="#TOC1">NAMED SUBPATTERNS</a><br> +<P> +Identifying capturing parentheses by number is simple, but it can be very hard +to keep track of the numbers in complicated regular expressions. Furthermore, +if an expression is modified, the numbers may change. To help with the +difficulty, PCRE supports the naming of subpatterns, something that Perl does +not provide. The Python syntax (?P<name>...) is used. Names consist of +alphanumeric characters and underscores, and must be unique within a pattern. +</P> +<P> +Named capturing parentheses are still allocated numbers as well as names. The +PCRE API provides function calls for extracting the name-to-number translation +table from a compiled pattern. For further details see the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<br><a name="SEC12" href="#TOC1">REPETITION</a><br> +<P> +Repetition is specified by quantifiers, which can follow any of the following +items: +</P> +<P> +<pre> + a literal data character + the . metacharacter + the \C escape sequence + escapes such as \d that match single characters + a character class + a back reference (see next section) + a parenthesized subpattern (unless it is an assertion) +</PRE> +</P> +<P> +The general repetition quantifier specifies a minimum and maximum number of +permitted matches, by giving the two numbers in curly brackets (braces), +separated by a comma. The numbers must be less than 65536, and the first must +be less than or equal to the second. For example: +</P> +<P> +<pre> + z{2,4} +</PRE> +</P> +<P> +matches "zz", "zzz", or "zzzz". A closing brace on its own is not a special +character. If the second number is omitted, but the comma is present, there is +no upper limit; if the second number and the comma are both omitted, the +quantifier specifies an exact number of required matches. Thus +</P> +<P> +<pre> + [aeiou]{3,} +</PRE> +</P> +<P> +matches at least 3 successive vowels, but may match many more, while +</P> +<P> +<pre> + \d{8} +</PRE> +</P> +<P> +matches exactly 8 digits. An opening curly bracket that appears in a position +where a quantifier is not allowed, or one that does not match the syntax of a +quantifier, is taken as a literal character. For example, {,6} is not a +quantifier, but a literal string of four characters. +</P> +<P> +In UTF-8 mode, quantifiers apply to UTF-8 characters rather than to individual +bytes. Thus, for example, \x{100}{2} matches two UTF-8 characters, each of +which is represented by a two-byte sequence. +</P> +<P> +The quantifier {0} is permitted, causing the expression to behave as if the +previous item and the quantifier were not present. +</P> +<P> +For convenience (and historical compatibility) the three most common +quantifiers have single-character abbreviations: +</P> +<P> +<pre> + * is equivalent to {0,} + + is equivalent to {1,} + ? is equivalent to {0,1} +</PRE> +</P> +<P> +It is possible to construct infinite loops by following a subpattern that can +match no characters with a quantifier that has no upper limit, for example: +</P> +<P> +<pre> + (a?)* +</PRE> +</P> +<P> +Earlier versions of Perl and PCRE used to give an error at compile time for +such patterns. However, because there are cases where this can be useful, such +patterns are now accepted, but if any repetition of the subpattern does in fact +match no characters, the loop is forcibly broken. +</P> +<P> +By default, the quantifiers are "greedy", that is, they match as much as +possible (up to the maximum number of permitted times), without causing the +rest of the pattern to fail. The classic example of where this gives problems +is in trying to match comments in C programs. These appear between the +sequences /* and */ and within the sequence, individual * and / characters may +appear. An attempt to match C comments by applying the pattern +</P> +<P> +<pre> + /\*.*\*/ +</PRE> +</P> +<P> +to the string +</P> +<P> +<pre> + /* first command */ not comment /* second comment */ +</PRE> +</P> +<P> +fails, because it matches the entire string owing to the greediness of the .* +item. +</P> +<P> +However, if a quantifier is followed by a question mark, it ceases to be +greedy, and instead matches the minimum number of times possible, so the +pattern +</P> +<P> +<pre> + /\*.*?\*/ +</PRE> +</P> +<P> +does the right thing with the C comments. The meaning of the various +quantifiers is not otherwise changed, just the preferred number of matches. +Do not confuse this use of question mark with its use as a quantifier in its +own right. Because it has two uses, it can sometimes appear doubled, as in +</P> +<P> +<pre> + \d??\d +</PRE> +</P> +<P> +which matches one digit by preference, but can match two if that is the only +way the rest of the pattern matches. +</P> +<P> +If the PCRE_UNGREEDY option is set (an option which is not available in Perl), +the quantifiers are not greedy by default, but individual ones can be made +greedy by following them with a question mark. In other words, it inverts the +default behaviour. +</P> +<P> +When a parenthesized subpattern is quantified with a minimum repeat count that +is greater than 1 or with a limited maximum, more store is required for the +compiled pattern, in proportion to the size of the minimum or maximum. +</P> +<P> +If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent +to Perl's /s) is set, thus allowing the . to match newlines, the pattern is +implicitly anchored, because whatever follows will be tried against every +character position in the subject string, so there is no point in retrying the +overall match at any position after the first. PCRE normally treats such a +pattern as though it were preceded by \A. +</P> +<P> +In cases where it is known that the subject string contains no newlines, it is +worth setting PCRE_DOTALL in order to obtain this optimization, or +alternatively using ^ to indicate anchoring explicitly. +</P> +<P> +However, there is one situation where the optimization cannot be used. When .* +is inside capturing parentheses that are the subject of a backreference +elsewhere in the pattern, a match at the start may fail, and a later one +succeed. Consider, for example: +</P> +<P> +<pre> + (.*)abc\1 +</PRE> +</P> +<P> +If the subject is "xyz123abc123" the match point is the fourth character. For +this reason, such a pattern is not implicitly anchored. +</P> +<P> +When a capturing subpattern is repeated, the value captured is the substring +that matched the final iteration. For example, after +</P> +<P> +<pre> + (tweedle[dume]{3}\s*)+ +</PRE> +</P> +<P> +has matched "tweedledum tweedledee" the value of the captured substring is +"tweedledee". However, if there are nested capturing subpatterns, the +corresponding captured values may have been set in previous iterations. For +example, after +</P> +<P> +<pre> + /(a|(b))+/ +</PRE> +</P> +<P> +matches "aba" the value of the second captured substring is "b". +</P> +<br><a name="SEC13" href="#TOC1">ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS</a><br> +<P> +With both maximizing and minimizing repetition, failure of what follows +normally causes the repeated item to be re-evaluated to see if a different +number of repeats allows the rest of the pattern to match. Sometimes it is +useful to prevent this, either to change the nature of the match, or to cause +it fail earlier than it otherwise might, when the author of the pattern knows +there is no point in carrying on. +</P> +<P> +Consider, for example, the pattern \d+foo when applied to the subject line +</P> +<P> +<pre> + 123456bar +</PRE> +</P> +<P> +After matching all 6 digits and then failing to match "foo", the normal +action of the matcher is to try again with only 5 digits matching the \d+ +item, and then with 4, and so on, before ultimately failing. "Atomic grouping" +(a term taken from Jeffrey Friedl's book) provides the means for specifying +that once a subpattern has matched, it is not to be re-evaluated in this way. +</P> +<P> +If we use atomic grouping for the previous example, the matcher would give up +immediately on failing to match "foo" the first time. The notation is a kind of +special parenthesis, starting with (?> as in this example: +</P> +<P> +<pre> + (?>\d+)foo +</PRE> +</P> +<P> +This kind of parenthesis "locks up" the part of the pattern it contains once +it has matched, and a failure further into the pattern is prevented from +backtracking into it. Backtracking past it to previous items, however, works as +normal. +</P> +<P> +An alternative description is that a subpattern of this type matches the string +of characters that an identical standalone pattern would match, if anchored at +the current point in the subject string. +</P> +<P> +Atomic grouping subpatterns are not capturing subpatterns. Simple cases such as +the above example can be thought of as a maximizing repeat that must swallow +everything it can. So, while both \d+ and \d+? are prepared to adjust the +number of digits they match in order to make the rest of the pattern match, +(?>\d+) can only match an entire sequence of digits. +</P> +<P> +Atomic groups in general can of course contain arbitrarily complicated +subpatterns, and can be nested. However, when the subpattern for an atomic +group is just a single repeated item, as in the example above, a simpler +notation, called a "possessive quantifier" can be used. This consists of an +additional + character following a quantifier. Using this notation, the +previous example can be rewritten as +</P> +<P> +<pre> + \d++bar +</PRE> +</P> +<P> +Possessive quantifiers are always greedy; the setting of the PCRE_UNGREEDY +option is ignored. They are a convenient notation for the simpler forms of +atomic group. However, there is no difference in the meaning or processing of a +possessive quantifier and the equivalent atomic group. +</P> +<P> +The possessive quantifier syntax is an extension to the Perl syntax. It +originates in Sun's Java package. +</P> +<P> +When a pattern contains an unlimited repeat inside a subpattern that can itself +be repeated an unlimited number of times, the use of an atomic group is the +only way to avoid some failing matches taking a very long time indeed. The +pattern +</P> +<P> +<pre> + (\D+|<\d+>)*[!?] +</PRE> +</P> +<P> +matches an unlimited number of substrings that either consist of non-digits, or +digits enclosed in <>, followed by either ! or ?. When it matches, it runs +quickly. However, if it is applied to +</P> +<P> +<pre> + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +</PRE> +</P> +<P> +it takes a long time before reporting failure. This is because the string can +be divided between the two repeats in a large number of ways, and all have to +be tried. (The example used [!?] rather than a single character at the end, +because both PCRE and Perl have an optimization that allows for fast failure +when a single character is used. They remember the last single character that +is required for a match, and fail early if it is not present in the string.) +If the pattern is changed to +</P> +<P> +<pre> + ((?>\D+)|<\d+>)*[!?] +</PRE> +</P> +<P> +sequences of non-digits cannot be broken, and failure happens quickly. +</P> +<br><a name="SEC14" href="#TOC1">BACK REFERENCES</a><br> +<P> +Outside a character class, a backslash followed by a digit greater than 0 (and +possibly further digits) is a back reference to a capturing subpattern earlier +(that is, to its left) in the pattern, provided there have been that many +previous capturing left parentheses. +</P> +<P> +However, if the decimal number following the backslash is less than 10, it is +always taken as a back reference, and causes an error only if there are not +that many capturing left parentheses in the entire pattern. In other words, the +parentheses that are referenced need not be to the left of the reference for +numbers less than 10. See the section entitled "Backslash" above for further +details of the handling of digits following a backslash. +</P> +<P> +A back reference matches whatever actually matched the capturing subpattern in +the current subject string, rather than anything matching the subpattern +itself (see +<a href="#subpatternsassubroutines">"Subpatterns as subroutines"</a> +below for a way of doing that). So the pattern +</P> +<P> +<pre> + (sens|respons)e and \1ibility +</PRE> +</P> +<P> +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If caseful matching is in force at the time of the +back reference, the case of letters is relevant. For example, +</P> +<P> +<pre> + ((?i)rah)\s+\1 +</PRE> +</P> +<P> +matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original +capturing subpattern is matched caselessly. +</P> +<P> +Back references to named subpatterns use the Python syntax (?P=name). We could +rewrite the above example as follows: +</P> +<P> +<pre> + (?<p1>(?i)rah)\s+(?P=p1) +</PRE> +</P> +<P> +There may be more than one back reference to the same subpattern. If a +subpattern has not actually been used in a particular match, any back +references to it always fail. For example, the pattern +</P> +<P> +<pre> + (a|(bc))\2 +</PRE> +</P> +<P> +always fails if it starts to match "a" rather than "bc". Because there may be +many capturing parentheses in a pattern, all digits following the backslash are +taken as part of a potential back reference number. If the pattern continues +with a digit character, some delimiter must be used to terminate the back +reference. If the PCRE_EXTENDED option is set, this can be whitespace. +Otherwise an empty comment can be used. +</P> +<P> +A back reference that occurs inside the parentheses to which it refers fails +when the subpattern is first used, so, for example, (a\1) never matches. +However, such references can be useful inside repeated subpatterns. For +example, the pattern +</P> +<P> +<pre> + (a|b\1)+ +</PRE> +</P> +<P> +matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration of +the subpattern, the back reference matches the character string corresponding +to the previous iteration. In order for this to work, the pattern must be such +that the first iteration does not need to match the back reference. This can be +done using alternation, as in the example above, or by a quantifier with a +minimum of zero. +</P> +<br><a name="SEC15" href="#TOC1">ASSERTIONS</a><br> +<P> +An assertion is a test on the characters following or preceding the current +matching point that does not actually consume any characters. The simple +assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described above. +More complicated assertions are coded as subpatterns. There are two kinds: +those that look ahead of the current position in the subject string, and those +that look behind it. +</P> +<P> +An assertion subpattern is matched in the normal way, except that it does not +cause the current matching position to be changed. Lookahead assertions start +with (?= for positive assertions and (?! for negative assertions. For example, +</P> +<P> +<pre> + \w+(?=;) +</PRE> +</P> +<P> +matches a word followed by a semicolon, but does not include the semicolon in +the match, and +</P> +<P> +<pre> + foo(?!bar) +</PRE> +</P> +<P> +matches any occurrence of "foo" that is not followed by "bar". Note that the +apparently similar pattern +</P> +<P> +<pre> + (?!foo)bar +</PRE> +</P> +<P> +does not find an occurrence of "bar" that is preceded by something other than +"foo"; it finds any occurrence of "bar" whatsoever, because the assertion +(?!foo) is always true when the next three characters are "bar". A +lookbehind assertion is needed to achieve this effect. +</P> +<P> +If you want to force a matching failure at some point in a pattern, the most +convenient way to do it is with (?!) because an empty string always matches, so +an assertion that requires there not to be an empty string must always fail. +</P> +<P> +Lookbehind assertions start with (?<= for positive assertions and (?<! for +negative assertions. For example, +</P> +<P> +<pre> + (?<!foo)bar +</PRE> +</P> +<P> +does find an occurrence of "bar" that is not preceded by "foo". The contents of +a lookbehind assertion are restricted such that all the strings it matches must +have a fixed length. However, if there are several alternatives, they do not +all have to have the same fixed length. Thus +</P> +<P> +<pre> + (?<=bullock|donkey) +</PRE> +</P> +<P> +is permitted, but +</P> +<P> +<pre> + (?<!dogs?|cats?) +</PRE> +</P> +<P> +causes an error at compile time. Branches that match different length strings +are permitted only at the top level of a lookbehind assertion. This is an +extension compared with Perl (at least for 5.8), which requires all branches to +match the same length of string. An assertion such as +</P> +<P> +<pre> + (?<=ab(c|de)) +</PRE> +</P> +<P> +is not permitted, because its single top-level branch can match two different +lengths, but it is acceptable if rewritten to use two top-level branches: +</P> +<P> +<pre> + (?<=abc|abde) +</PRE> +</P> +<P> +The implementation of lookbehind assertions is, for each alternative, to +temporarily move the current position back by the fixed width and then try to +match. If there are insufficient characters before the current position, the +match is deemed to fail. +</P> +<P> +PCRE does not allow the \C escape (which matches a single byte in UTF-8 mode) +to appear in lookbehind assertions, because it makes it impossible to calculate +the length of the lookbehind. +</P> +<P> +Atomic groups can be used in conjunction with lookbehind assertions to specify +efficient matching at the end of the subject string. Consider a simple pattern +such as +</P> +<P> +<pre> + abcd$ +</PRE> +</P> +<P> +when applied to a long string that does not match. Because matching proceeds +from left to right, PCRE will look for each "a" in the subject and then see if +what follows matches the rest of the pattern. If the pattern is specified as +</P> +<P> +<pre> + ^.*abcd$ +</PRE> +</P> +<P> +the initial .* matches the entire string at first, but when this fails (because +there is no following "a"), it backtracks to match all but the last character, +then all but the last two characters, and so on. Once again the search for "a" +covers the entire string, from right to left, so we are no better off. However, +if the pattern is written as +</P> +<P> +<pre> + ^(?>.*)(?<=abcd) +</PRE> +</P> +<P> +or, equivalently, +</P> +<P> +<pre> + ^.*+(?<=abcd) +</PRE> +</P> +<P> +there can be no backtracking for the .* item; it can match only the entire +string. The subsequent lookbehind assertion does a single test on the last four +characters. If it fails, the match fails immediately. For long strings, this +approach makes a significant difference to the processing time. +</P> +<P> +Several assertions (of any sort) may occur in succession. For example, +</P> +<P> +<pre> + (?<=\d{3})(?<!999)foo +</PRE> +</P> +<P> +matches "foo" preceded by three digits that are not "999". Notice that each of +the assertions is applied independently at the same point in the subject +string. First there is a check that the previous three characters are all +digits, and then there is a check that the same three characters are not "999". +This pattern does <i>not</i> match "foo" preceded by six characters, the first +of which are digits and the last three of which are not "999". For example, it +doesn't match "123abcfoo". A pattern to do that is +</P> +<P> +<pre> + (?<=\d{3}...)(?<!999)foo +</PRE> +</P> +<P> +This time the first assertion looks at the preceding six characters, checking +that the first three are digits, and then the second assertion checks that the +preceding three characters are not "999". +</P> +<P> +Assertions can be nested in any combination. For example, +</P> +<P> +<pre> + (?<=(?<!foo)bar)baz +</PRE> +</P> +<P> +matches an occurrence of "baz" that is preceded by "bar" which in turn is not +preceded by "foo", while +</P> +<P> +<pre> + (?<=\d{3}(?!999)...)foo +</PRE> +</P> +<P> +is another pattern which matches "foo" preceded by three digits and any three +characters that are not "999". +</P> +<P> +Assertion subpatterns are not capturing subpatterns, and may not be repeated, +because it makes no sense to assert the same thing several times. If any kind +of assertion contains capturing subpatterns within it, these are counted for +the purposes of numbering the capturing subpatterns in the whole pattern. +However, substring capturing is carried out only for positive assertions, +because it does not make sense for negative assertions. +</P> +<br><a name="SEC16" href="#TOC1">CONDITIONAL SUBPATTERNS</a><br> +<P> +It is possible to cause the matching process to obey a subpattern +conditionally or to choose between two alternative subpatterns, depending on +the result of an assertion, or whether a previous capturing subpattern matched +or not. The two possible forms of conditional subpattern are +</P> +<P> +<pre> + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) +</PRE> +</P> +<P> +If the condition is satisfied, the yes-pattern is used; otherwise the +no-pattern (if present) is used. If there are more than two alternatives in the +subpattern, a compile-time error occurs. +</P> +<P> +There are three kinds of condition. If the text between the parentheses +consists of a sequence of digits, the condition is satisfied if the capturing +subpattern of that number has previously matched. The number must be greater +than zero. Consider the following pattern, which contains non-significant white +space to make it more readable (assume the PCRE_EXTENDED option) and to divide +it into three parts for ease of discussion: +</P> +<P> +<pre> + ( \( )? [^()]+ (?(1) \) ) +</PRE> +</P> +<P> +The first part matches an optional opening parenthesis, and if that +character is present, sets it as the first captured substring. The second part +matches one or more characters that are not parentheses. The third part is a +conditional subpattern that tests whether the first set of parentheses matched +or not. If they did, that is, if subject started with an opening parenthesis, +the condition is true, and so the yes-pattern is executed and a closing +parenthesis is required. Otherwise, since no-pattern is not present, the +subpattern matches nothing. In other words, this pattern matches a sequence of +non-parentheses, optionally enclosed in parentheses. +</P> +<P> +If the condition is the string (R), it is satisfied if a recursive call to the +pattern or subpattern has been made. At "top level", the condition is false. +This is a PCRE extension. Recursive patterns are described in the next section. +</P> +<P> +If the condition is not a sequence of digits or (R), it must be an assertion. +This may be a positive or negative lookahead or lookbehind assertion. Consider +this pattern, again containing non-significant white space, and with the two +alternatives on the second line: +</P> +<P> +<pre> + (?(?=[^a-z]*[a-z]) + \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) +</PRE> +</P> +<P> +The condition is a positive lookahead assertion that matches an optional +sequence of non-letters followed by a letter. In other words, it tests for the +presence of at least one letter in the subject. If a letter is found, the +subject is matched against the first alternative; otherwise it is matched +against the second. This pattern matches strings in one of the two forms +dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. +</P> +<br><a name="SEC17" href="#TOC1">COMMENTS</a><br> +<P> +The sequence (?# marks the start of a comment which continues up to the next +closing parenthesis. Nested parentheses are not permitted. The characters +that make up a comment play no part in the pattern matching at all. +</P> +<P> +If the PCRE_EXTENDED option is set, an unescaped # character outside a +character class introduces a comment that continues up to the next newline +character in the pattern. +</P> +<br><a name="SEC18" href="#TOC1">RECURSIVE PATTERNS</a><br> +<P> +Consider the problem of matching a string in parentheses, allowing for +unlimited nested parentheses. Without the use of recursion, the best that can +be done is to use a pattern that matches up to some fixed depth of nesting. It +is not possible to handle an arbitrary nesting depth. Perl has provided an +experimental facility that allows regular expressions to recurse (amongst other +things). It does this by interpolating Perl code in the expression at run time, +and the code can refer to the expression itself. A Perl pattern to solve the +parentheses problem can be created like this: +</P> +<P> +<pre> + $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; +</PRE> +</P> +<P> +The (?p{...}) item interpolates Perl code at run time, and in this case refers +recursively to the pattern in which it appears. Obviously, PCRE cannot support +the interpolation of Perl code. Instead, it supports some special syntax for +recursion of the entire pattern, and also for individual subpattern recursion. +</P> +<P> +The special item that consists of (? followed by a number greater than zero and +a closing parenthesis is a recursive call of the subpattern of the given +number, provided that it occurs inside that subpattern. (If not, it is a +"subroutine" call, which is described in the next section.) The special item +(?R) is a recursive call of the entire regular expression. +</P> +<P> +For example, this PCRE pattern solves the nested parentheses problem (assume +the PCRE_EXTENDED option is set so that white space is ignored): +</P> +<P> +<pre> + \( ( (?>[^()]+) | (?R) )* \) +</PRE> +</P> +<P> +First it matches an opening parenthesis. Then it matches any number of +substrings which can either be a sequence of non-parentheses, or a recursive +match of the pattern itself (that is a correctly parenthesized substring). +Finally there is a closing parenthesis. +</P> +<P> +If this were part of a larger pattern, you would not want to recurse the entire +pattern, so instead you could use this: +</P> +<P> +<pre> + ( \( ( (?>[^()]+) | (?1) )* \) ) +</PRE> +</P> +<P> +We have put the pattern into parentheses, and caused the recursion to refer to +them instead of the whole pattern. In a larger pattern, keeping track of +parenthesis numbers can be tricky. It may be more convenient to use named +parentheses instead. For this, PCRE uses (?P>name), which is an extension to +the Python syntax that PCRE uses for named parentheses (Perl does not provide +named parentheses). We could rewrite the above example as follows: +</P> +<P> +<pre> + (?P<pn> \( ( (?>[^()]+) | (?P>pn) )* \) ) +</PRE> +</P> +<P> +This particular example pattern contains nested unlimited repeats, and so the +use of atomic grouping for matching strings of non-parentheses is important +when applying the pattern to strings that do not match. For example, when this +pattern is applied to +</P> +<P> +<pre> + (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() +</PRE> +</P> +<P> +it yields "no match" quickly. However, if atomic grouping is not used, +the match runs for a very long time indeed because there are so many different +ways the + and * repeats can carve up the subject, and all have to be tested +before failure can be reported. +</P> +<P> +At the end of a match, the values set for any capturing subpatterns are those +from the outermost level of the recursion at which the subpattern value is set. +If you want to obtain intermediate values, a callout function can be used (see +below and the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation). If the pattern above is matched against +</P> +<P> +<pre> + (ab(cd)ef) +</PRE> +</P> +<P> +the value for the capturing parentheses is "ef", which is the last value taken +on at the top level. If additional parentheses are added, giving +</P> +<P> +<pre> + \( ( ( (?>[^()]+) | (?R) )* ) \) + ^ ^ + ^ ^ +</PRE> +</P> +<P> +the string they capture is "ab(cd)ef", the contents of the top level +parentheses. If there are more than 15 capturing parentheses in a pattern, PCRE +has to obtain extra memory to store data during a recursion, which it does by +using <b>pcre_malloc</b>, freeing it via <b>pcre_free</b> afterwards. If no +memory can be obtained, the match fails with the PCRE_ERROR_NOMEMORY error. +</P> +<P> +Do not confuse the (?R) item with the condition (R), which tests for recursion. +Consider this pattern, which matches text in angle brackets, allowing for +arbitrary nesting. Only digits are allowed in nested brackets (that is, when +recursing), whereas any characters are permitted at the outer level. +</P> +<P> +<pre> + < (?: (?(R) \d++ | [^<>]*+) | (?R)) * > +</PRE> +</P> +<P> +In this pattern, (?(R) is the start of a conditional subpattern, with two +different alternatives for the recursive and non-recursive cases. The (?R) item +is the actual recursive call. +</P> +<a name="subpatternsassubroutines"></a><br><a name="SEC19" href="#TOC1">SUBPATTERNS AS SUBROUTINES</a><br> +<P> +If the syntax for a recursive subpattern reference (either by number or by +name) is used outside the parentheses to which it refers, it operates like a +subroutine in a programming language. An earlier example pointed out that the +pattern +</P> +<P> +<pre> + (sens|respons)e and \1ibility +</PRE> +</P> +<P> +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If instead the pattern +</P> +<P> +<pre> + (sens|respons)e and (?1)ibility +</PRE> +</P> +<P> +is used, it does match "sense and responsibility" as well as the other two +strings. Such references must, however, follow the subpattern to which they +refer. +</P> +<br><a name="SEC20" href="#TOC1">CALLOUTS</a><br> +<P> +Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl +code to be obeyed in the middle of matching a regular expression. This makes it +possible, amongst other things, to extract different substrings that match the +same pair of parentheses when there is a repetition. +</P> +<P> +PCRE provides a similar feature, but of course it cannot obey arbitrary Perl +code. The feature is called "callout". The caller of PCRE provides an external +function by putting its entry point in the global variable <i>pcre_callout</i>. +By default, this variable contains NULL, which disables all calling out. +</P> +<P> +Within a regular expression, (?C) indicates the points at which the external +function is to be called. If you want to identify different callout points, you +can put a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: +</P> +<P> +<pre> + (?C1)\dabc(?C2)def +</PRE> +</P> +<P> +During matching, when PCRE reaches a callout point (and <i>pcre_callout</i> is +set), the external function is called. It is provided with the number of the +callout, and, optionally, one item of data originally supplied by the caller of +<b>pcre_exec()</b>. The callout function may cause matching to backtrack, or to +fail altogether. A complete description of the interface to the callout +function is given in the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +Last updated: 03 February 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcreperform.html b/external-libs/pcre/doc/html/pcreperform.html new file mode 100644 index 00000000..418ac6d4 --- /dev/null +++ b/external-libs/pcre/doc/html/pcreperform.html @@ -0,0 +1,93 @@ +<html> +<head> +<title>pcreperform specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE PERFORMANCE</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE PERFORMANCE</a><br> +<P> +Certain items that may appear in regular expression patterns are more efficient +than others. It is more efficient to use a character class like [aeiou] than a +set of alternatives such as (a|e|i|o|u). In general, the simplest construction +that provides the required behaviour is usually the most efficient. Jeffrey +Friedl's book contains a lot of discussion about optimizing regular expressions +for efficient performance. +</P> +<P> +When a pattern begins with .* not in parentheses, or in parentheses that are +not the subject of a backreference, and the PCRE_DOTALL option is set, the +pattern is implicitly anchored by PCRE, since it can match only at the start of +a subject string. However, if PCRE_DOTALL is not set, PCRE cannot make this +optimization, because the . metacharacter does not then match a newline, and if +the subject string contains newlines, the pattern may match from the character +immediately following one of them instead of from the very start. For example, +the pattern +</P> +<P> +<pre> + .*second +</PRE> +</P> +<P> +matches the subject "first\nand second" (where \n stands for a newline +character), with the match starting at the seventh character. In order to do +this, PCRE has to retry the match starting after every newline in the subject. +</P> +<P> +If you are using such a pattern with subject strings that do not contain +newlines, the best performance is obtained by setting PCRE_DOTALL, or starting +the pattern with ^.* to indicate explicit anchoring. That saves PCRE from +having to scan along the subject looking for a newline to restart at. +</P> +<P> +Beware of patterns that contain nested indefinite repeats. These can take a +long time to run when applied to a string that does not match. Consider the +pattern fragment +</P> +<P> +<pre> + (a+)* +</PRE> +</P> +<P> +This can match "aaaa" in 33 different ways, and this number increases very +rapidly as the string gets longer. (The * repeat can match 0, 1, 2, 3, or 4 +times, and for each of those cases other than 0, the + repeats can match +different numbers of times.) When the remainder of the pattern is such that the +entire match is going to fail, PCRE has in principle to try every possible +variation, and this can take an extremely long time. +</P> +<P> +An optimization catches some of the more simple cases such as +</P> +<P> +<pre> + (a+)*b +</PRE> +</P> +<P> +where a literal character follows. Before embarking on the standard matching +procedure, PCRE checks that there is a "b" later in the subject string, and if +there is not, it fails the match immediately. However, when there is no +following literal this optimization cannot be used. You can see the difference +by comparing the behaviour of +</P> +<P> +<pre> + (a+)*\d +</PRE> +</P> +<P> +with the pattern above. The former gives a failure almost instantly when +applied to a whole line of "a" characters, whereas the latter takes an +appreciable time with strings longer than about 20 characters. +</P> +<P> +Last updated: 03 February 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcreposix.html b/external-libs/pcre/doc/html/pcreposix.html new file mode 100644 index 00000000..d0a5e127 --- /dev/null +++ b/external-libs/pcre/doc/html/pcreposix.html @@ -0,0 +1,237 @@ +<html> +<head> +<title>pcreposix specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS OF POSIX API</a> +<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> +<li><a name="TOC3" href="#SEC3">COMPILING A PATTERN</a> +<li><a name="TOC4" href="#SEC4">MATCHING NEWLINE CHARACTERS</a> +<li><a name="TOC5" href="#SEC5">MATCHING A PATTERN</a> +<li><a name="TOC6" href="#SEC6">ERROR MESSAGES</a> +<li><a name="TOC7" href="#SEC7">STORAGE</a> +<li><a name="TOC8" href="#SEC8">AUTHOR</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS OF POSIX API</a><br> +<P> +<b>#include <pcreposix.h></b> +</P> +<P> +<b>int regcomp(regex_t *<i>preg</i>, const char *<i>pattern</i>,</b> +<b>int <i>cflags</i>);</b> +</P> +<P> +<b>int regexec(regex_t *<i>preg</i>, const char *<i>string</i>,</b> +<b>size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b> +</P> +<P> +<b>size_t regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b> +<b>char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b> +</P> +<P> +<b>void regfree(regex_t *<i>preg</i>);</b> +</P> +<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> +<P> +This set of functions provides a POSIX-style API to the PCRE regular expression +package. See the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation for a description of the native API, which contains additional +functionality. +</P> +<P> +The functions described here are just wrapper functions that ultimately call +the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b> +header file, and on Unix systems the library itself is called +<b>pcreposix.a</b>, so can be accessed by adding <b>-lpcreposix</b> to the +command for linking an application which uses them. Because the POSIX functions +call the native ones, it is also necessary to add \fR-lpcre\fR. +</P> +<P> +I have implemented only those option bits that can be reasonably mapped to PCRE +native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined +with the value zero. They have no effect, but since programs that are written +to the POSIX interface often use them, this makes it easier to slot in PCRE as +a replacement library. Other POSIX options are not even defined. +</P> +<P> +When PCRE is called via these functions, it is only the API that is POSIX-like +in style. The syntax and semantics of the regular expressions themselves are +still those of Perl, subject to the setting of various PCRE options, as +described below. "POSIX-like in style" means that the API approximates to the +POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding +domains it is probably even less compatible. +</P> +<P> +The header for these functions is supplied as <b>pcreposix.h</b> to avoid any +potential clash with other POSIX libraries. It can, of course, be renamed or +aliased as <b>regex.h</b>, which is the "correct" name. It provides two +structure types, <i>regex_t</i> for compiled internal forms, and +<i>regmatch_t</i> for returning captured substrings. It also defines some +constants whose names start with "REG_"; these are used for setting options and +identifying error codes. +</P> +<br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br> +<P> +The function <b>regcomp()</b> is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer +to a regex_t structure which is used as a base for storing information about +the compiled expression. +</P> +<P> +The argument <i>cflags</i> is either zero, or contains one or more of the bits +defined by the following macros: +</P> +<P> +<pre> + REG_ICASE +</PRE> +</P> +<P> +The PCRE_CASELESS option is set when the expression is passed for compilation +to the native function. +</P> +<P> +<pre> + REG_NEWLINE +</PRE> +</P> +<P> +The PCRE_MULTILINE option is set when the expression is passed for compilation +to the native function. Note that this does <i>not</i> mimic the defined POSIX +behaviour for REG_NEWLINE (see the following section). +</P> +<P> +In the absence of these flags, no options are passed to the native function. +This means the the regex is compiled with PCRE default semantics. In +particular, the way it handles newline characters in the subject string is the +Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only +<i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way +newlines are matched by . (they aren't) or by a negative class such as [^a] +(they are). +</P> +<P> +The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The +<i>preg</i> structure is filled in on success, and one member of the structure +is public: <i>re_nsub</i> contains the number of capturing subpatterns in +the regular expression. Various error codes are defined in the header file. +</P> +<br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br> +<P> +This area is not simple, because POSIX and Perl take different views of things. +It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never +intended to be a POSIX engine. The following table lists the different +possibilities for matching newline characters in PCRE: +</P> +<P> +<pre> + Default Change with +</PRE> +</P> +<P> +<pre> + . matches newline no PCRE_DOTALL + newline matches [^a] yes not changeable + $ matches \n at end yes PCRE_DOLLARENDONLY + $ matches \n in middle no PCRE_MULTILINE + ^ matches \n in middle no PCRE_MULTILINE +</PRE> +</P> +<P> +This is the equivalent table for POSIX: +</P> +<P> +<pre> + Default Change with +</PRE> +</P> +<P> +<pre> + . matches newline yes REG_NEWLINE + newline matches [^a] yes REG_NEWLINE + $ matches \n at end no REG_NEWLINE + $ matches \n in middle no REG_NEWLINE + ^ matches \n in middle no REG_NEWLINE +</PRE> +</P> +<P> +PCRE's behaviour is the same as Perl's, except that there is no equivalent for +PCRE_DOLLARENDONLY in Perl. In both PCRE and Perl, there is no way to stop +newline from matching [^a]. +</P> +<P> +The default POSIX newline handling can be obtained by setting PCRE_DOTALL and +PCRE_DOLLARENDONLY, but there is no way to make PCRE behave exactly as for the +REG_NEWLINE action. +</P> +<br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br> +<P> +The function <b>regexec()</b> is called to match a pre-compiled pattern +<i>preg</i> against a given <i>string</i>, which is terminated by a zero byte, +subject to the options in <i>eflags</i>. These can be: +</P> +<P> +<pre> + REG_NOTBOL +</PRE> +</P> +<P> +The PCRE_NOTBOL option is set when calling the underlying PCRE matching +function. +</P> +<P> +<pre> + REG_NOTEOL +</PRE> +</P> +<P> +The PCRE_NOTEOL option is set when calling the underlying PCRE matching +function. +</P> +<P> +The portion of the string that was matched, and also any captured substrings, +are returned via the <i>pmatch</i> argument, which points to an array of +<i>nmatch</i> structures of type <i>regmatch_t</i>, containing the members +<i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first character of +each substring and the offset to the first character after the end of each +substring, respectively. The 0th element of the vector relates to the entire +portion of <i>string</i> that was matched; subsequent elements relate to the +capturing subpatterns of the regular expression. Unused entries in the array +have both structure members set to -1. +</P> +<P> +A successful match yields a zero return; various error codes are defined in the +header file, of which REG_NOMATCH is the "expected" failure code. +</P> +<br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br> +<P> +The <b>regerror()</b> function maps a non-zero errorcode from either +<b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not +NULL, the error should have arisen from the use of that structure. A message +terminated by a binary zero is placed in <i>errbuf</i>. The length of the +message, including the zero, is limited to <i>errbuf_size</i>. The yield of the +function is the size of buffer needed to hold the whole message. +</P> +<br><a name="SEC7" href="#TOC1">STORAGE</a><br> +<P> +Compiling a regular expression causes memory to be allocated and associated +with the <i>preg</i> structure. The function <b>regfree()</b> frees all such +memory, after which <i>preg</i> may no longer be used as a compiled expression. +</P> +<br><a name="SEC8" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel <ph10@cam.ac.uk> +<br> +University Computing Service, +<br> +Cambridge CB2 3QG, England. +</P> +<P> +Last updated: 03 February 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcresample.html b/external-libs/pcre/doc/html/pcresample.html new file mode 100644 index 00000000..fed41f62 --- /dev/null +++ b/external-libs/pcre/doc/html/pcresample.html @@ -0,0 +1,79 @@ +<html> +<head> +<title>pcresample specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">PCRE SAMPLE PROGRAM</a> +</ul> +<br><a name="SEC1" href="#TOC1">PCRE SAMPLE PROGRAM</a><br> +<P> +A simple, complete demonstration program, to get you started with using PCRE, +is supplied in the file <i>pcredemo.c</i> in the PCRE distribution. +</P> +<P> +The program compiles the regular expression that is its first argument, and +matches it against the subject string in its second argument. No PCRE options +are set, and default character tables are used. If matching succeeds, the +program outputs the portion of the subject that matched, together with the +contents of any captured substrings. +</P> +<P> +If the -g option is given on the command line, the program then goes on to +check for further matches of the same regular expression in the same subject +string. The logic is a little bit tricky because of the possibility of matching +an empty string. Comments in the code explain what is going on. +</P> +<P> +On a Unix system that has PCRE installed in <i>/usr/local</i>, you can compile +the demonstration program using a command like this: +</P> +<P> +<pre> + gcc -o pcredemo pcredemo.c -I/usr/local/include \ + -L/usr/local/lib -lpcre +</PRE> +</P> +<P> +Then you can run simple tests like this: +</P> +<P> +<pre> + ./pcredemo 'cat|dog' 'the cat sat on the mat' + ./pcredemo -g 'cat|dog' 'the dog sat on the cat' +</PRE> +</P> +<P> +Note that there is a much more comprehensive test program, called +<b>pcretest</b>, which supports many more facilities for testing regular +expressions and the PCRE library. The <b>pcredemo</b> program is provided as a +simple coding example. +</P> +<P> +On some operating systems (e.g. Solaris) you may get an error like this when +you try to run <b>pcredemo</b>: +</P> +<P> +<pre> + ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory +</PRE> +</P> +<P> +This is caused by the way shared library support works on those systems. You +need to add +</P> +<P> +<pre> + -R/usr/local/lib +</PRE> +</P> +<P> +to the compile command to get round this problem. +</P> +<P> +Last updated: 28 January 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/html/pcretest.html b/external-libs/pcre/doc/html/pcretest.html new file mode 100644 index 00000000..2ba9893d --- /dev/null +++ b/external-libs/pcre/doc/html/pcretest.html @@ -0,0 +1,443 @@ +<html> +<head> +<title>pcretest specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">SYNOPSIS</a> +<li><a name="TOC2" href="#SEC2">OPTIONS</a> +<li><a name="TOC3" href="#SEC3">DESCRIPTION</a> +<li><a name="TOC4" href="#SEC4">PATTERN MODIFIERS</a> +<li><a name="TOC5" href="#SEC5">CALLOUTS</a> +<li><a name="TOC6" href="#SEC6">DATA LINES</a> +<li><a name="TOC7" href="#SEC7">OUTPUT FROM PCRETEST</a> +<li><a name="TOC8" href="#SEC8">AUTHOR</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</a><br> +<P> +<b>pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]</b> +</P> +<P> +<b>pcretest</b> was written as a test program for the PCRE regular expression +library itself, but it can also be used for experimenting with regular +expressions. This document describes the features of the test program; for +details of the regular expressions themselves, see the +<a href="pcrepattern.html"><b>pcrepattern</b></a> +documentation. For details of PCRE and its options, see the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation. +</P> +<br><a name="SEC2" href="#TOC1">OPTIONS</a><br> +<P> +<b>-C</b> +Output the version number of the PCRE library, and all available information +about the optional features that are included, and then exit. +</P> +<P> +<b>-d</b> +Behave as if each regex had the <b>/D</b> modifier (see below); the internal +form is output after compilation. +</P> +<P> +<b>-i</b> +Behave as if each regex had the <b>/I</b> modifier; information about the +compiled pattern is given after compilation. +</P> +<P> +<b>-m</b> +Output the size of each compiled pattern after it has been compiled. This is +equivalent to adding /M to each regular expression. For compatibility with +earlier versions of pcretest, <b>-s</b> is a synonym for <b>-m</b>. +</P> +<P> +<b>-o</b> <i>osize</i> +Set the number of elements in the output vector that is used when calling PCRE +to be <i>osize</i>. The default value is 45, which is enough for 14 capturing +subexpressions. The vector size can be changed for individual matching calls by +including \O in the data line (see below). +</P> +<P> +<b>-p</b> +Behave as if each regex has <b>/P</b> modifier; the POSIX wrapper API is used +to call PCRE. None of the other options has any effect when <b>-p</b> is set. +</P> +<P> +<b>-t</b> +Run each compile, study, and match many times with a timer, and output +resulting time per compile or match (in milliseconds). Do not set <b>-t</b> with +<b>-m</b>, because you will then get the size output 20000 times and the timing +will be distorted. +</P> +<br><a name="SEC3" href="#TOC1">DESCRIPTION</a><br> +<P> +If <b>pcretest</b> is given two filename arguments, it reads from the first and +writes to the second. If it is given only one filename argument, it reads from +that file and writes to stdout. Otherwise, it reads from stdin and writes to +stdout, and prompts for each line of input, using "re>" to prompt for regular +expressions, and "data>" to prompt for data lines. +</P> +<P> +The program handles any number of sets of input on a single input file. Each +set starts with a regular expression, and continues with any number of data +lines to be matched against the pattern. +</P> +<P> +Each line is matched separately and independently. If you want to do +multiple-line matches, you have to use the \n escape sequence in a single line +of input to encode the newline characters. The maximum length of data line is +30,000 characters. +</P> +<P> +An empty line signals the end of the data lines, at which point a new regular +expression is read. The regular expressions are given enclosed in any +non-alphameric delimiters other than backslash, for example +</P> +<P> +<pre> + /(a|bc)x+yz/ +</PRE> +</P> +<P> +White space before the initial delimiter is ignored. A regular expression may +be continued over several input lines, in which case the newline characters are +included within it. It is possible to include the delimiter within the pattern +by escaping it, for example +</P> +<P> +<pre> + /abc\/def/ +</PRE> +</P> +<P> +If you do so, the escape and the delimiter form part of the pattern, but since +delimiters are always non-alphameric, this does not affect its interpretation. +If the terminating delimiter is immediately followed by a backslash, for +example, +</P> +<P> +<pre> + /abc/\ +</PRE> +</P> +<P> +then a backslash is added to the end of the pattern. This is done to provide a +way of testing the error condition that arises if a pattern finishes with a +backslash, because +</P> +<P> +<pre> + /abc\/ +</PRE> +</P> +<P> +is interpreted as the first line of a pattern that starts with "abc/", causing +pcretest to read the next line as a continuation of the regular expression. +</P> +<br><a name="SEC4" href="#TOC1">PATTERN MODIFIERS</a><br> +<P> +The pattern may be followed by <b>i</b>, <b>m</b>, <b>s</b>, or <b>x</b> to set the +PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, +respectively. For example: +</P> +<P> +<pre> + /caseless/i +</PRE> +</P> +<P> +These modifier letters have the same effect as they do in Perl. There are +others that set PCRE options that do not correspond to anything in Perl: +<b>/A</b>, <b>/E</b>, <b>/N</b>, <b>/U</b>, and <b>/X</b> set PCRE_ANCHORED, +PCRE_DOLLAR_ENDONLY, PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, and PCRE_EXTRA +respectively. +</P> +<P> +Searching for all possible matches within each subject string can be requested +by the <b>/g</b> or <b>/G</b> modifier. After finding a match, PCRE is called +again to search the remainder of the subject string. The difference between +<b>/g</b> and <b>/G</b> is that the former uses the <i>startoffset</i> argument to +<b>pcre_exec()</b> to start searching at a new point within the entire string +(which is in effect what Perl does), whereas the latter passes over a shortened +substring. This makes a difference to the matching process if the pattern +begins with a lookbehind assertion (including \b or \B). +</P> +<P> +If any call to <b>pcre_exec()</b> in a <b>/g</b> or <b>/G</b> sequence matches an +empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED +flags set in order to search for another, non-empty, match at the same point. +If this second match fails, the start offset is advanced by one, and the normal +match is retried. This imitates the way Perl handles such cases when using the +<b>/g</b> modifier or the <b>split()</b> function. +</P> +<P> +There are a number of other modifiers for controlling the way <b>pcretest</b> +operates. +</P> +<P> +The <b>/+</b> modifier requests that as well as outputting the substring that +matched the entire pattern, pcretest should in addition output the remainder of +the subject string. This is useful for tests where the subject contains +multiple copies of the same substring. +</P> +<P> +The <b>/L</b> modifier must be followed directly by the name of a locale, for +example, +</P> +<P> +<pre> + /pattern/Lfr +</PRE> +</P> +<P> +For this reason, it must be the last modifier letter. The given locale is set, +<b>pcre_maketables()</b> is called to build a set of character tables for the +locale, and this is then passed to <b>pcre_compile()</b> when compiling the +regular expression. Without an <b>/L</b> modifier, NULL is passed as the tables +pointer; that is, <b>/L</b> applies only to the expression on which it appears. +</P> +<P> +The <b>/I</b> modifier requests that <b>pcretest</b> output information about the +compiled expression (whether it is anchored, has a fixed first character, and +so on). It does this by calling <b>pcre_fullinfo()</b> after compiling an +expression, and outputting the information it gets back. If the pattern is +studied, the results of that are also output. +</P> +<P> +The <b>/D</b> modifier is a PCRE debugging feature, which also assumes <b>/I</b>. +It causes the internal form of compiled regular expressions to be output after +compilation. If the pattern was studied, the information returned is also +output. +</P> +<P> +The <b>/S</b> modifier causes <b>pcre_study()</b> to be called after the +expression has been compiled, and the results used when the expression is +matched. +</P> +<P> +The <b>/M</b> modifier causes the size of memory block used to hold the compiled +pattern to be output. +</P> +<P> +The <b>/P</b> modifier causes <b>pcretest</b> to call PCRE via the POSIX wrapper +API rather than its native API. When this is done, all other modifiers except +<b>/i</b>, <b>/m</b>, and <b>/+</b> are ignored. REG_ICASE is set if <b>/i</b> is +present, and REG_NEWLINE is set if <b>/m</b> is present. The wrapper functions +force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set. +</P> +<P> +The <b>/8</b> modifier causes <b>pcretest</b> to call PCRE with the PCRE_UTF8 +option set. This turns on support for UTF-8 character handling in PCRE, +provided that it was compiled with this support enabled. This modifier also +causes any non-printing characters in output strings to be printed using the +\x{hh...} notation if they are valid UTF-8 sequences. +</P> +<P> +If the <b>/?</b> modifier is used with <b>/8</b>, it causes <b>pcretest</b> to +call <b>pcre_compile()</b> with the PCRE_NO_UTF8_CHECK option, to suppress the +checking of the string for UTF-8 validity. +</P> +<br><a name="SEC5" href="#TOC1">CALLOUTS</a><br> +<P> +If the pattern contains any callout requests, <b>pcretest</b>'s callout function +will be called. By default, it displays the callout number, and the start and +current positions in the text at the callout time. For example, the output +</P> +<P> +<pre> + --->pqrabcdef + 0 ^ ^ +</PRE> +</P> +<P> +indicates that callout number 0 occurred for a match attempt starting at the +fourth character of the subject string, when the pointer was at the seventh +character. The callout function returns zero (carry on matching) by default. +</P> +<P> +Inserting callouts may be helpful when using <b>pcretest</b> to check +complicated regular expressions. For further information about callouts, see +the +<a href="pcrecallout.html"><b>pcrecallout</b></a> +documentation. +</P> +<P> +For testing the PCRE library, additional control of callout behaviour is +available via escape sequences in the data, as described in the following +section. In particular, it is possible to pass in a number as callout data (the +default is zero). If the callout function receives a non-zero number, it +returns that value instead of zero. +</P> +<br><a name="SEC6" href="#TOC1">DATA LINES</a><br> +<P> +Before each data line is passed to <b>pcre_exec()</b>, leading and trailing +whitespace is removed, and it is then scanned for \ escapes. Some of these are +pretty esoteric features, intended for checking out some of the more +complicated features of PCRE. If you are just testing "ordinary" regular +expressions, you probably don't need any of these. The following escapes are +recognized: +</P> +<P> +<pre> + \a alarm (= BEL) + \b backspace + \e escape + \f formfeed + \n newline + \r carriage return + \t tab + \v vertical tab + \nnn octal character (up to 3 octal digits) + \xhh hexadecimal character (up to 2 hex digits) + \x{hh...} hexadecimal character, any number of digits + in UTF-8 mode + \A pass the PCRE_ANCHORED option to <b>pcre_exec()</b> + \B pass the PCRE_NOTBOL option to <b>pcre_exec()</b> + \Cdd call pcre_copy_substring() for substring dd + after a successful match (any decimal number + less than 32) + \Cname call pcre_copy_named_substring() for substring + "name" after a successful match (name termin- + ated by next non alphanumeric character) + \C+ show the current captured substrings at callout + time + \C- do not supply a callout function + \C!n return 1 instead of 0 when callout number n is + reached + \C!n!m return 1 instead of 0 when callout number n is + reached for the nth time + \C*n pass the number n (may be negative) as callout + data + \Gdd call pcre_get_substring() for substring dd + after a successful match (any decimal number + less than 32) + \Gname call pcre_get_named_substring() for substring + "name" after a successful match (name termin- + ated by next non-alphanumeric character) + \L call pcre_get_substringlist() after a + successful match + \M discover the minimum MATCH_LIMIT setting + \N pass the PCRE_NOTEMPTY option to <b>pcre_exec()</b> + \Odd set the size of the output vector passed to + <b>pcre_exec()</b> to dd (any number of decimal + digits) + \S output details of memory get/free calls during matching + \Z pass the PCRE_NOTEOL option to <b>pcre_exec()</b> + \? pass the PCRE_NO_UTF8_CHECK option to + <b>pcre_exec()</b> +</PRE> +</P> +<P> +If \M is present, <b>pcretest</b> calls <b>pcre_exec()</b> several times, with +different values in the <i>match_limit</i> field of the <b>pcre_extra</b> data +structure, until it finds the minimum number that is needed for +<b>pcre_exec()</b> to complete. This number is a measure of the amount of +recursion and backtracking that takes place, and checking it out can be +instructive. For most simple matches, the number is quite small, but for +patterns with very large numbers of matching possibilities, it can become large +very quickly with increasing length of subject string. +</P> +<P> +When \O is used, it may be higher or lower than the size set by the <b>-O</b> +option (or defaulted to 45); \O applies only to the call of <b>pcre_exec()</b> +for the line in which it appears. +</P> +<P> +A backslash followed by anything else just escapes the anything else. If the +very last character is a backslash, it is ignored. This gives a way of passing +an empty line as data, since a real empty line terminates the data input. +</P> +<P> +If <b>/P</b> was present on the regex, causing the POSIX wrapper API to be used, +only <b>\B</b>, and <b>\Z</b> have any effect, causing REG_NOTBOL and REG_NOTEOL +to be passed to <b>regexec()</b> respectively. +</P> +<P> +The use of \x{hh...} to represent UTF-8 characters is not dependent on the use +of the <b>/8</b> modifier on the pattern. It is recognized always. There may be +any number of hexadecimal digits inside the braces. The result is from one to +six bytes, encoded according to the UTF-8 rules. +</P> +<br><a name="SEC7" href="#TOC1">OUTPUT FROM PCRETEST</a><br> +<P> +When a match succeeds, pcretest outputs the list of captured substrings that +<b>pcre_exec()</b> returns, starting with number 0 for the string that matched +the whole pattern. Here is an example of an interactive pcretest run. +</P> +<P> +<pre> + $ pcretest + PCRE version 4.00 08-Jan-2003 +</PRE> +</P> +<P> +<pre> + re> /^abc(\d+)/ + data> abc123 + 0: abc123 + 1: 123 + data> xyz + No match +</PRE> +</P> +<P> +If the strings contain any non-printing characters, they are output as \0x +escapes, or as \x{...} escapes if the <b>/8</b> modifier was present on the +pattern. If the pattern has the <b>/+</b> modifier, then the output for +substring 0 is followed by the the rest of the subject string, identified by +"0+" like this: +</P> +<P> +<pre> + re> /cat/+ + data> cataract + 0: cat + 0+ aract +</PRE> +</P> +<P> +If the pattern has the <b>/g</b> or <b>/G</b> modifier, the results of successive +matching attempts are output in sequence, like this: +</P> +<P> +<pre> + re> /\Bi(\w\w)/g + data> Mississippi + 0: iss + 1: ss + 0: iss + 1: ss + 0: ipp + 1: pp +</PRE> +</P> +<P> +"No match" is output only if the first match attempt fails. +</P> +<P> +If any of the sequences <b>\C</b>, <b>\G</b>, or <b>\L</b> are present in a +data line that is successfully matched, the substrings extracted by the +convenience functions are output with C, G, or L after the string number +instead of a colon. This is in addition to the normal full list. The string +length (that is, the return from the extraction function) is given in +parentheses after each string for <b>\C</b> and <b>\G</b>. +</P> +<P> +Note that while patterns can be continued over several lines (a plain ">" +prompt is used for continuations), data lines may not. However newlines can be +included in data by means of the \n escape. +</P> +<br><a name="SEC8" href="#TOC1">AUTHOR</a><br> +<P> +Philip Hazel <ph10@cam.ac.uk> +<br> +University Computing Service, +<br> +Cambridge CB2 3QG, England. +</P> +<P> +Last updated: 09 December 2003 +<br> +Copyright © 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcre.3 b/external-libs/pcre/doc/pcre.3 new file mode 100644 index 00000000..c0c71419 --- /dev/null +++ b/external-libs/pcre/doc/pcre.3 @@ -0,0 +1,174 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH DESCRIPTION +.rs +.sp +The PCRE library is a set of functions that implement regular expression +pattern matching using the same syntax and semantics as Perl, with just a few +differences. The current implementation of PCRE (release 4.x) corresponds +approximately with Perl 5.8, including support for UTF-8 encoded strings. +However, this support has to be explicitly enabled; it is not the default. + +PCRE is written in C and released as a C library. However, a number of people +have written wrappers and interfaces of various kinds. A C++ class is included +in these contributions, which can be found in the \fIContrib\fR directory at +the primary FTP site, which is: + +.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre"> +.\" </a> +ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre + +Details of exactly which Perl regular expression features are and are not +supported by PCRE are given in separate documents. See the +.\" HREF +\fBpcrepattern\fR +.\" +and +.\" HREF +\fBpcrecompat\fR +.\" +pages. + +Some features of PCRE can be included, excluded, or changed when the library is +built. The +.\" HREF +\fBpcre_config()\fR +.\" +function makes it possible for a client to discover which features are +available. Documentation about building PCRE for various operating systems can +be found in the \fBREADME\fR file in the source distribution. + +.SH USER DOCUMENTATION +.rs +.sp +The user documentation for PCRE has been split up into a number of different +sections. In the "man" format, each of these is a separate "man page". In the +HTML format, each is a separate page, linked from the index page. In the plain +text format, all the sections are concatenated, for ease of searching. The +sections are as follows: + + pcre this document + pcreapi details of PCRE's native API + pcrebuild options for building PCRE + pcrecallout details of the callout feature + pcrecompat discussion of Perl compatibility + pcregrep description of the \fBpcregrep\fR command + pcrepattern syntax and semantics of supported + regular expressions + pcreperform discussion of performance issues + pcreposix the POSIX-compatible API + pcresample discussion of the sample program + pcretest the \fBpcretest\fR testing command + +In addition, in the "man" and HTML formats, there is a short page for each +library function, listing its arguments and results. + +.SH LIMITATIONS +.rs +.sp +There are some size limitations in PCRE but it is hoped that they will never in +practice be relevant. + +The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE is +compiled with the default internal linkage size of 2. If you want to process +regular expressions that are truly enormous, you can compile PCRE with an +internal linkage size of 3 or 4 (see the \fBREADME\fR file in the source +distribution and the +.\" HREF +\fBpcrebuild\fR +.\" +documentation for details). If these cases the limit is substantially larger. +However, the speed of execution will be slower. + +All values in repeating quantifiers must be less than 65536. +The maximum number of capturing subpatterns is 65535. + +There is no limit to the number of non-capturing subpatterns, but the maximum +depth of nesting of all kinds of parenthesized subpattern, including capturing +subpatterns, assertions, and other types of subpattern, is 200. + +The maximum length of a subject string is the largest positive number that an +integer variable can hold. However, PCRE uses recursion to handle subpatterns +and indefinite repetition. This means that the available stack space may limit +the size of a subject string that can be processed by certain patterns. + +.\" HTML <a name="utf8support"></a> +.SH UTF-8 SUPPORT +.rs +.sp +Starting at release 3.3, PCRE has had some support for character strings +encoded in the UTF-8 format. For release 4.0 this has been greatly extended to +cover most common requirements. + +In order process UTF-8 strings, you must build PCRE to include UTF-8 support in +the code, and, in addition, you must call +.\" HREF +\fBpcre_compile()\fR +.\" +with the PCRE_UTF8 option flag. When you do this, both the pattern and any +subject strings that are matched against it are treated as UTF-8 strings +instead of just strings of bytes. + +If you compile PCRE with UTF-8 support, but do not use it at run time, the +library will be a bit bigger, but the additional run time overhead is limited +to testing the PCRE_UTF8 flag in several places, so should not be very large. + +The following comments apply when PCRE is running in UTF-8 mode: + +1. When you set the PCRE_UTF8 flag, the strings passed as patterns and subjects +are checked for validity on entry to the relevant functions. If an invalid +UTF-8 string is passed, an error return is given. In some situations, you may +already know that your strings are valid, and therefore want to skip these +checks in order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag +at compile time or at run time, PCRE assumes that the pattern or subject it +is given (respectively) contains only valid UTF-8 codes. In this case, it does +not diagnose an invalid UTF-8 string. If you pass an invalid UTF-8 string to +PCRE when PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program +may crash. + +2. In a pattern, the escape sequence \\x{...}, where the contents of the braces +is a string of hexadecimal digits, is interpreted as a UTF-8 character whose +code number is the given hexadecimal number, for example: \\x{1234}. If a +non-hexadecimal digit appears between the braces, the item is not recognized. +This escape sequence can be used either as a literal, or within a character +class. + +3. The original hexadecimal escape sequence, \\xhh, matches a two-byte UTF-8 +character if the value is greater than 127. + +4. Repeat quantifiers apply to complete UTF-8 characters, not to individual +bytes, for example: \\x{100}{3}. + +5. The dot metacharacter matches one UTF-8 character instead of a single byte. + +6. The escape sequence \\C can be used to match a single byte in UTF-8 mode, +but its use can lead to some strange effects. + +7. The character escapes \\b, \\B, \\d, \\D, \\s, \\S, \\w, and \\W correctly +test characters of any code value, but the characters that PCRE recognizes as +digits, spaces, or word characters remain the same set as before, all with +values less than 256. + +8. Case-insensitive matching applies only to characters whose values are less +than 256. PCRE does not support the notion of "case" for higher-valued +characters. + +9. PCRE does not support the use of Unicode tables and properties or the Perl +escapes \\p, \\P, and \\X. + +.SH AUTHOR +.rs +.sp +Philip Hazel <ph10@cam.ac.uk> +.br +University Computing Service, +.br +Cambridge CB2 3QG, England. +.br +Phone: +44 1223 334714 + +.in 0 +Last updated: 20 August 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcre.txt b/external-libs/pcre/doc/pcre.txt new file mode 100644 index 00000000..698baa52 --- /dev/null +++ b/external-libs/pcre/doc/pcre.txt @@ -0,0 +1,3169 @@ +This file contains a concatenation of the PCRE man pages, converted to plain +text format for ease of searching with a text editor, or for use on systems +that do not have a man page processor. The small individual files that give +synopses of each function in the library have not been included. There are +separate text files for the pcregrep and pcretest commands. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +DESCRIPTION + + The PCRE library is a set of functions that implement regular expres- + sion pattern matching using the same syntax and semantics as Perl, with + just a few differences. The current implementation of PCRE (release + 4.x) corresponds approximately with Perl 5.8, including support for + UTF-8 encoded strings. However, this support has to be explicitly + enabled; it is not the default. + + PCRE is written in C and released as a C library. However, a number of + people have written wrappers and interfaces of various kinds. A C++ + class is included in these contributions, which can be found in the + Contrib directory at the primary FTP site, which is: + + ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre + + Details of exactly which Perl regular expression features are and are + not supported by PCRE are given in separate documents. See the pcrepat- + tern and pcrecompat pages. + + Some features of PCRE can be included, excluded, or changed when the + library is built. The pcre_config() function makes it possible for a + client to discover which features are available. Documentation about + building PCRE for various operating systems can be found in the README + file in the source distribution. + + +USER DOCUMENTATION + + The user documentation for PCRE has been split up into a number of dif- + ferent sections. In the "man" format, each of these is a separate "man + page". In the HTML format, each is a separate page, linked from the + index page. In the plain text format, all the sections are concate- + nated, for ease of searching. The sections are as follows: + + pcre this document + pcreapi details of PCRE's native API + pcrebuild options for building PCRE + pcrecallout details of the callout feature + pcrecompat discussion of Perl compatibility + pcregrep description of the pcregrep command + pcrepattern syntax and semantics of supported + regular expressions + pcreperform discussion of performance issues + pcreposix the POSIX-compatible API + pcresample discussion of the sample program + pcretest the pcretest testing command + + In addition, in the "man" and HTML formats, there is a short page for + each library function, listing its arguments and results. + + +LIMITATIONS + + There are some size limitations in PCRE but it is hoped that they will + never in practice be relevant. + + The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE + is compiled with the default internal linkage size of 2. If you want to + process regular expressions that are truly enormous, you can compile + PCRE with an internal linkage size of 3 or 4 (see the README file in + the source distribution and the pcrebuild documentation for details). + If these cases the limit is substantially larger. However, the speed + of execution will be slower. + + All values in repeating quantifiers must be less than 65536. The maxi- + mum number of capturing subpatterns is 65535. + + There is no limit to the number of non-capturing subpatterns, but the + maximum depth of nesting of all kinds of parenthesized subpattern, + including capturing subpatterns, assertions, and other types of subpat- + tern, is 200. + + The maximum length of a subject string is the largest positive number + that an integer variable can hold. However, PCRE uses recursion to han- + dle subpatterns and indefinite repetition. This means that the avail- + able stack space may limit the size of a subject string that can be + processed by certain patterns. + + +UTF-8 SUPPORT + + Starting at release 3.3, PCRE has had some support for character + strings encoded in the UTF-8 format. For release 4.0 this has been + greatly extended to cover most common requirements. + + In order process UTF-8 strings, you must build PCRE to include UTF-8 + support in the code, and, in addition, you must call pcre_compile() + with the PCRE_UTF8 option flag. When you do this, both the pattern and + any subject strings that are matched against it are treated as UTF-8 + strings instead of just strings of bytes. + + If you compile PCRE with UTF-8 support, but do not use it at run time, + the library will be a bit bigger, but the additional run time overhead + is limited to testing the PCRE_UTF8 flag in several places, so should + not be very large. + + The following comments apply when PCRE is running in UTF-8 mode: + + 1. When you set the PCRE_UTF8 flag, the strings passed as patterns and + subjects are checked for validity on entry to the relevant functions. + If an invalid UTF-8 string is passed, an error return is given. In some + situations, you may already know that your strings are valid, and + therefore want to skip these checks in order to improve performance. If + you set the PCRE_NO_UTF8_CHECK flag at compile time or at run time, + PCRE assumes that the pattern or subject it is given (respectively) + contains only valid UTF-8 codes. In this case, it does not diagnose an + invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE when + PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program may + crash. + + 2. In a pattern, the escape sequence \x{...}, where the contents of the + braces is a string of hexadecimal digits, is interpreted as a UTF-8 + character whose code number is the given hexadecimal number, for exam- + ple: \x{1234}. If a non-hexadecimal digit appears between the braces, + the item is not recognized. This escape sequence can be used either as + a literal, or within a character class. + + 3. The original hexadecimal escape sequence, \xhh, matches a two-byte + UTF-8 character if the value is greater than 127. + + 4. Repeat quantifiers apply to complete UTF-8 characters, not to indi- + vidual bytes, for example: \x{100}{3}. + + 5. The dot metacharacter matches one UTF-8 character instead of a + single byte. + + 6. The escape sequence \C can be used to match a single byte in UTF-8 + mode, but its use can lead to some strange effects. + + 7. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly + test characters of any code value, but the characters that PCRE recog- + nizes as digits, spaces, or word characters remain the same set as + before, all with values less than 256. + + 8. Case-insensitive matching applies only to characters whose values + are less than 256. PCRE does not support the notion of "case" for + higher-valued characters. + + 9. PCRE does not support the use of Unicode tables and properties or + the Perl escapes \p, \P, and \X. + + +AUTHOR + + Philip Hazel <ph10@cam.ac.uk> + University Computing Service, + Cambridge CB2 3QG, England. + Phone: +44 1223 334714 + +Last updated: 20 August 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE BUILD-TIME OPTIONS + + This document describes the optional features of PCRE that can be + selected when the library is compiled. They are all selected, or dese- + lected, by providing options to the configure script which is run + before the make command. The complete list of options for configure + (which includes the standard ones such as the selection of the instal- + lation directory) can be obtained by running + + ./configure --help + + The following sections describe certain options whose names begin with + --enable or --disable. These settings specify changes to the defaults + for the configure command. Because of the way that configure works, + --enable and --disable always come in pairs, so the complementary + option always exists as well, but as it specifies the default, it is + not described. + + +UTF-8 SUPPORT + + To build PCRE with support for UTF-8 character strings, add + + --enable-utf8 + + to the configure command. Of itself, this does not make PCRE treat + strings as UTF-8. As well as compiling PCRE with this option, you also + have have to set the PCRE_UTF8 option when you call the pcre_compile() + function. + + +CODE VALUE OF NEWLINE + + By default, PCRE treats character 10 (linefeed) as the newline charac- + ter. This is the normal newline character on Unix-like systems. You can + compile PCRE to use character 13 (carriage return) instead by adding + + --enable-newline-is-cr + + to the configure command. For completeness there is also a --enable- + newline-is-lf option, which explicitly specifies linefeed as the new- + line character. + + +BUILDING SHARED AND STATIC LIBRARIES + + The PCRE building process uses libtool to build both shared and static + Unix libraries by default. You can suppress one of these by adding one + of + + --disable-shared + --disable-static + + to the configure command, as required. + + +POSIX MALLOC USAGE + + When PCRE is called through the POSIX interface (see the pcreposix + documentation), additional working storage is required for holding the + pointers to capturing substrings because PCRE requires three integers + per substring, whereas the POSIX interface provides only two. If the + number of expected substrings is small, the wrapper function uses space + on the stack, because this is faster than using malloc() for each call. + The default threshold above which the stack is no longer used is 10; it + can be changed by adding a setting such as + + --with-posix-malloc-threshold=20 + + to the configure command. + + +LIMITING PCRE RESOURCE USAGE + + Internally, PCRE has a function called match() which it calls repeat- + edly (possibly recursively) when performing a matching operation. By + limiting the number of times this function may be called, a limit can + be placed on the resources used by a single call to pcre_exec(). The + limit can be changed at run time, as described in the pcreapi documen- + tation. The default is 10 million, but this can be changed by adding a + setting such as + + --with-match-limit=500000 + + to the configure command. + + +HANDLING VERY LARGE PATTERNS + + Within a compiled pattern, offset values are used to point from one + part to another (for example, from an opening parenthesis to an alter- + nation metacharacter). By default two-byte values are used for these + offsets, leading to a maximum size for a compiled pattern of around + 64K. This is sufficient to handle all but the most gigantic patterns. + Nevertheless, some people do want to process enormous patterns, so it + is possible to compile PCRE to use three-byte or four-byte offsets by + adding a setting such as + + --with-link-size=3 + + to the configure command. The value given must be 2, 3, or 4. Using + longer offsets slows down the operation of PCRE because it has to load + additional bytes when handling them. + + If you build PCRE with an increased link size, test 2 (and test 5 if + you are using UTF-8) will fail. Part of the output of these tests is a + representation of the compiled pattern, and this changes with the link + size. + + +AVOIDING EXCESSIVE STACK USAGE + + PCRE implements backtracking while matching by making recursive calls + to an internal function called match(). In environments where the size + of the stack is limited, this can severely limit PCRE's operation. (The + Unix environment does not usually suffer from this problem.) An alter- + native approach that uses memory from the heap to remember data, + instead of using recursive function calls, has been implemented to work + round this problem. If you want to build a version of PCRE that works + this way, add + + --disable-stack-for-recursion + + to the configure command. With this configuration, PCRE will use the + pcre_stack_malloc and pcre_stack_free variables to call memory + management functions. Separate functions are provided because the usage + is very predictable: the block sizes requested are always the same, and + the blocks are always freed in reverse order. A calling program might + be able to implement optimized functions that perform better than the + standard malloc() and free() functions. PCRE runs noticeably more + slowly when built in this way. + + +USING EBCDIC CODE + + PCRE assumes by default that it will run in an environment where the + character code is ASCII (or UTF-8, which is a superset of ASCII). PCRE + can, however, be compiled to run in an EBCDIC environment by adding + + --enable-ebcdic + + to the configure command. + +Last updated: 09 December 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +SYNOPSIS OF PCRE API + + #include <pcre.h> + + pcre *pcre_compile(const char *pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + pcre_extra *pcre_study(const pcre *code, int options, + const char **errptr); + + int pcre_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + int pcre_copy_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + char *buffer, int buffersize); + + int pcre_copy_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, char *buffer, + int buffersize); + + int pcre_get_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + const char **stringptr); + + int pcre_get_stringnumber(const pcre *code, + const char *name); + + int pcre_get_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, + const char **stringptr); + + int pcre_get_substring_list(const char *subject, + int *ovector, int stringcount, const char ***listptr); + + void pcre_free_substring(const char *stringptr); + + void pcre_free_substring_list(const char **stringptr); + + const unsigned char *pcre_maketables(void); + + int pcre_fullinfo(const pcre *code, const pcre_extra *extra, + int what, void *where); + + int pcre_info(const pcre *code, int *optptr, int *firstcharptr); + + int pcre_config(int what, void *where); + + char *pcre_version(void); + + void *(*pcre_malloc)(size_t); + + void (*pcre_free)(void *); + + void *(*pcre_stack_malloc)(size_t); + + void (*pcre_stack_free)(void *); + + int (*pcre_callout)(pcre_callout_block *); + + +PCRE API + + PCRE has its own native API, which is described in this document. There + is also a set of wrapper functions that correspond to the POSIX regular + expression API. These are described in the pcreposix documentation. + + The native API function prototypes are defined in the header file + pcre.h, and on Unix systems the library itself is called libpcre.a, so + can be accessed by adding -lpcre to the command for linking an applica- + tion which calls it. The header file defines the macros PCRE_MAJOR and + PCRE_MINOR to contain the major and minor release numbers for the + library. Applications can use these to include support for different + releases. + + The functions pcre_compile(), pcre_study(), and pcre_exec() are used + for compiling and matching regular expressions. A sample program that + demonstrates the simplest way of using them is given in the file pcre- + demo.c. The pcresample documentation describes how to run it. + + There are convenience functions for extracting captured substrings from + a matched subject string. They are: + + pcre_copy_substring() + pcre_copy_named_substring() + pcre_get_substring() + pcre_get_named_substring() + pcre_get_substring_list() + + pcre_free_substring() and pcre_free_substring_list() are also provided, + to free the memory used for extracted strings. + + The function pcre_maketables() is used (optionally) to build a set of + character tables in the current locale for passing to pcre_compile(). + + The function pcre_fullinfo() is used to find out information about a + compiled pattern; pcre_info() is an obsolete version which returns only + some of the available information, but is retained for backwards com- + patibility. The function pcre_version() returns a pointer to a string + containing the version of PCRE and its date of release. + + The global variables pcre_malloc and pcre_free initially contain the + entry points of the standard malloc() and free() functions respec- + tively. PCRE calls the memory management functions via these variables, + so a calling program can replace them if it wishes to intercept the + calls. This should be done before calling any PCRE functions. + + The global variables pcre_stack_malloc and pcre_stack_free are also + indirections to memory management functions. These special functions + are used only when PCRE is compiled to use the heap for remembering + data, instead of recursive function calls. This is a non-standard way + of building PCRE, for use in environments that have limited stacks. + Because of the greater use of memory management, it runs more slowly. + Separate functions are provided so that special-purpose external code + can be used for this case. When used, these functions are always called + in a stack-like manner (last obtained, first freed), and always for + memory blocks of the same size. + + The global variable pcre_callout initially contains NULL. It can be set + by the caller to a "callout" function, which PCRE will then call at + specified points during a matching operation. Details are given in the + pcrecallout documentation. + + +MULTITHREADING + + The PCRE functions can be used in multi-threading applications, with + the proviso that the memory management functions pointed to by + pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the + callout function pointed to by pcre_callout, are shared by all threads. + + The compiled form of a regular expression is not altered during match- + ing, so the same compiled pattern can safely be used by several threads + at once. + + +CHECKING BUILD-TIME OPTIONS + + int pcre_config(int what, void *where); + + The function pcre_config() makes it possible for a PCRE client to dis- + cover which optional features have been compiled into the PCRE library. + The pcrebuild documentation has more details about these optional fea- + tures. + + The first argument for pcre_config() is an integer, specifying which + information is required; the second argument is a pointer to a variable + into which the information is placed. The following information is + available: + + PCRE_CONFIG_UTF8 + + The output is an integer that is set to one if UTF-8 support is avail- + able; otherwise it is set to zero. + + PCRE_CONFIG_NEWLINE + + The output is an integer that is set to the value of the code that is + used for the newline character. It is either linefeed (10) or carriage + return (13), and should normally be the standard character for your + operating system. + + PCRE_CONFIG_LINK_SIZE + + The output is an integer that contains the number of bytes used for + internal linkage in compiled regular expressions. The value is 2, 3, or + 4. Larger values allow larger regular expressions to be compiled, at + the expense of slower matching. The default value of 2 is sufficient + for all but the most massive patterns, since it allows the compiled + pattern to be up to 64K in size. + + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + + The output is an integer that contains the threshold above which the + POSIX interface uses malloc() for output vectors. Further details are + given in the pcreposix documentation. + + PCRE_CONFIG_MATCH_LIMIT + + The output is an integer that gives the default limit for the number of + internal matching function calls in a pcre_exec() execution. Further + details are given with pcre_exec() below. + + PCRE_CONFIG_STACKRECURSE + + The output is an integer that is set to one if internal recursion is + implemented by recursive function calls that use the stack to remember + their state. This is the usual way that PCRE is compiled. The output is + zero if PCRE was compiled to use blocks of data on the heap instead of + recursive function calls. In this case, pcre_stack_malloc and + pcre_stack_free are called to manage memory blocks on the heap, thus + avoiding the use of the stack. + + +COMPILING A PATTERN + + pcre *pcre_compile(const char *pattern, int options, + const char **errptr, int *erroffset, + const unsigned char *tableptr); + + + The function pcre_compile() is called to compile a pattern into an + internal form. The pattern is a C string terminated by a binary zero, + and is passed in the argument pattern. A pointer to a single block of + memory that is obtained via pcre_malloc is returned. This contains the + compiled code and related data. The pcre type is defined for the + returned block; this is a typedef for a structure whose contents are + not externally defined. It is up to the caller to free the memory when + it is no longer required. + + Although the compiled code of a PCRE regex is relocatable, that is, it + does not depend on memory location, the complete pcre data block is not + fully relocatable, because it contains a copy of the tableptr argument, + which is an address (see below). + + The options argument contains independent bits that affect the compila- + tion. It should be zero if no options are required. Some of the + options, in particular, those that are compatible with Perl, can also + be set and unset from within the pattern (see the detailed description + of regular expressions in the pcrepattern documentation). For these + options, the contents of the options argument specifies their initial + settings at the start of compilation and execution. The PCRE_ANCHORED + option can be set at the time of matching as well as at compile time. + + If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise, + if compilation of a pattern fails, pcre_compile() returns NULL, and + sets the variable pointed to by errptr to point to a textual error mes- + sage. The offset from the start of the pattern to the character where + the error was discovered is placed in the variable pointed to by + erroffset, which must not be NULL. If it is, an immediate error is + given. + + If the final argument, tableptr, is NULL, PCRE uses a default set of + character tables which are built when it is compiled, using the default + C locale. Otherwise, tableptr must be the result of a call to + pcre_maketables(). See the section on locale support below. + + This code fragment shows a typical straightforward call to pcre_com- + pile(): + + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ + + The following option bits are defined: + + PCRE_ANCHORED + + If this bit is set, the pattern is forced to be "anchored", that is, it + is constrained to match only at the first matching point in the string + which is being searched (the "subject string"). This effect can also be + achieved by appropriate constructs in the pattern itself, which is the + only way to do it in Perl. + + PCRE_CASELESS + + If this bit is set, letters in the pattern match both upper and lower + case letters. It is equivalent to Perl's /i option, and it can be + changed within a pattern by a (?i) option setting. + + PCRE_DOLLAR_ENDONLY + + If this bit is set, a dollar metacharacter in the pattern matches only + at the end of the subject string. Without this option, a dollar also + matches immediately before the final character if it is a newline (but + not before any other newlines). The PCRE_DOLLAR_ENDONLY option is + ignored if PCRE_MULTILINE is set. There is no equivalent to this option + in Perl, and no way to set it within a pattern. + + PCRE_DOTALL + + If this bit is set, a dot metacharater in the pattern matches all char- + acters, including newlines. Without it, newlines are excluded. This + option is equivalent to Perl's /s option, and it can be changed within + a pattern by a (?s) option setting. A negative class such as [^a] + always matches a newline character, independent of the setting of this + option. + + PCRE_EXTENDED + + If this bit is set, whitespace data characters in the pattern are + totally ignored except when escaped or inside a character class. + Whitespace does not include the VT character (code 11). In addition, + characters between an unescaped # outside a character class and the + next newline character, inclusive, are also ignored. This is equivalent + to Perl's /x option, and it can be changed within a pattern by a (?x) + option setting. + + This option makes it possible to include comments inside complicated + patterns. Note, however, that this applies only to data characters. + Whitespace characters may never appear within special character + sequences in a pattern, for example within the sequence (?( which + introduces a conditional subpattern. + + PCRE_EXTRA + + This option was invented in order to turn on additional functionality + of PCRE that is incompatible with Perl, but it is currently of very + little use. When set, any backslash in a pattern that is followed by a + letter that has no special meaning causes an error, thus reserving + these combinations for future expansion. By default, as in Perl, a + backslash followed by a letter with no special meaning is treated as a + literal. There are at present no other features controlled by this + option. It can also be set by a (?X) option setting within a pattern. + + PCRE_MULTILINE + + By default, PCRE treats the subject string as consisting of a single + "line" of characters (even if it actually contains several newlines). + The "start of line" metacharacter (^) matches only at the start of the + string, while the "end of line" metacharacter ($) matches only at the + end of the string, or before a terminating newline (unless PCRE_DOL- + LAR_ENDONLY is set). This is the same as Perl. + + When PCRE_MULTILINE it is set, the "start of line" and "end of line" + constructs match immediately following or immediately before any new- + line in the subject string, respectively, as well as at the very start + and end. This is equivalent to Perl's /m option, and it can be changed + within a pattern by a (?m) option setting. If there are no "\n" charac- + ters in a subject string, or no occurrences of ^ or $ in a pattern, + setting PCRE_MULTILINE has no effect. + + PCRE_NO_AUTO_CAPTURE + + If this option is set, it disables the use of numbered capturing paren- + theses in the pattern. Any opening parenthesis that is not followed by + ? behaves as if it were followed by ?: but named parentheses can still + be used for capturing (and they acquire numbers in the usual way). + There is no equivalent of this option in Perl. + + PCRE_UNGREEDY + + This option inverts the "greediness" of the quantifiers so that they + are not greedy by default, but become greedy if followed by "?". It is + not compatible with Perl. It can also be set by a (?U) option setting + within the pattern. + + PCRE_UTF8 + + This option causes PCRE to regard both the pattern and the subject as + strings of UTF-8 characters instead of single-byte character strings. + However, it is available only if PCRE has been built to include UTF-8 + support. If not, the use of this option provokes an error. Details of + how this option changes the behaviour of PCRE are given in the section + on UTF-8 support in the main pcre page. + + PCRE_NO_UTF8_CHECK + + When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is + automatically checked. If an invalid UTF-8 sequence of bytes is found, + pcre_compile() returns an error. If you already know that your pattern + is valid, and you want to skip this check for performance reasons, you + can set the PCRE_NO_UTF8_CHECK option. When it is set, the effect of + passing an invalid UTF-8 string as a pattern is undefined. It may cause + your program to crash. Note that there is a similar option for sup- + pressing the checking of subject strings passed to pcre_exec(). + + + +STUDYING A PATTERN + + pcre_extra *pcre_study(const pcre *code, int options, + const char **errptr); + + When a pattern is going to be used several times, it is worth spending + more time analyzing it in order to speed up the time taken for match- + ing. The function pcre_study() takes a pointer to a compiled pattern as + its first argument. If studing the pattern produces additional informa- + tion that will help speed up matching, pcre_study() returns a pointer + to a pcre_extra block, in which the study_data field points to the + results of the study. + + The returned value from a pcre_study() can be passed directly to + pcre_exec(). However, the pcre_extra block also contains other fields + that can be set by the caller before the block is passed; these are + described below. If studying the pattern does not produce any addi- + tional information, pcre_study() returns NULL. In that circumstance, if + the calling program wants to pass some of the other fields to + pcre_exec(), it must set up its own pcre_extra block. + + The second argument contains option bits. At present, no options are + defined for pcre_study(), and this argument should always be zero. + + The third argument for pcre_study() is a pointer for an error message. + If studying succeeds (even if no data is returned), the variable it + points to is set to NULL. Otherwise it points to a textual error mes- + sage. You should therefore test the error pointer for NULL after call- + ing pcre_study(), to be sure that it has run successfully. + + This is a typical call to pcre_study(): + + pcre_extra *pe; + pe = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options exist */ + &error); /* set to NULL or points to a message */ + + At present, studying a pattern is useful only for non-anchored patterns + that do not have a single fixed starting character. A bitmap of possi- + ble starting characters is created. + + +LOCALE SUPPORT + + PCRE handles caseless matching, and determines whether characters are + letters, digits, or whatever, by reference to a set of tables. When + running in UTF-8 mode, this applies only to characters with codes less + than 256. The library contains a default set of tables that is created + in the default C locale when PCRE is compiled. This is used when the + final argument of pcre_compile() is NULL, and is sufficient for many + applications. + + An alternative set of tables can, however, be supplied. Such tables are + built by calling the pcre_maketables() function, which has no argu- + ments, in the relevant locale. The result can then be passed to + pcre_compile() as often as necessary. For example, to build and use + tables that are appropriate for the French locale (where accented char- + acters with codes greater than 128 are treated as letters), the follow- + ing code could be used: + + setlocale(LC_CTYPE, "fr"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); + + The tables are built in memory that is obtained via pcre_malloc. The + pointer that is passed to pcre_compile is saved with the compiled pat- + tern, and the same tables are used via this pointer by pcre_study() and + pcre_exec(). Thus, for any single pattern, compilation, studying and + matching all happen in the same locale, but different patterns can be + compiled in different locales. It is the caller's responsibility to + ensure that the memory containing the tables remains available for as + long as it is needed. + + +INFORMATION ABOUT A PATTERN + + int pcre_fullinfo(const pcre *code, const pcre_extra *extra, + int what, void *where); + + The pcre_fullinfo() function returns information about a compiled pat- + tern. It replaces the obsolete pcre_info() function, which is neverthe- + less retained for backwards compability (and is documented below). + + The first argument for pcre_fullinfo() is a pointer to the compiled + pattern. The second argument is the result of pcre_study(), or NULL if + the pattern was not studied. The third argument specifies which piece + of information is required, and the fourth argument is a pointer to a + variable to receive the data. The yield of the function is zero for + success, or one of the following negative numbers: + + PCRE_ERROR_NULL the argument code was NULL + the argument where was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of what was invalid + + Here is a typical call of pcre_fullinfo(), to obtain the length of the + compiled pattern: + + int rc; + unsigned long int length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + pe, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ + + The possible values for the third argument are defined in pcre.h, and + are as follows: + + PCRE_INFO_BACKREFMAX + + Return the number of the highest back reference in the pattern. The + fourth argument should point to an int variable. Zero is returned if + there are no back references. + + PCRE_INFO_CAPTURECOUNT + + Return the number of capturing subpatterns in the pattern. The fourth + argument should point to an int variable. + + PCRE_INFO_FIRSTBYTE + + Return information about the first byte of any matched string, for a + non-anchored pattern. (This option used to be called + PCRE_INFO_FIRSTCHAR; the old name is still recognized for backwards + compatibility.) + + If there is a fixed first byte, e.g. from a pattern such as + (cat|cow|coyote), it is returned in the integer pointed to by where. + Otherwise, if either + + (a) the pattern was compiled with the PCRE_MULTILINE option, and every + branch starts with "^", or + + (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not + set (if it were set, the pattern would be anchored), + + -1 is returned, indicating that the pattern matches only at the start + of a subject string or after any newline within the string. Otherwise + -2 is returned. For anchored patterns, -2 is returned. + + PCRE_INFO_FIRSTTABLE + + If the pattern was studied, and this resulted in the construction of a + 256-bit table indicating a fixed set of bytes for the first byte in any + matching string, a pointer to the table is returned. Otherwise NULL is + returned. The fourth argument should point to an unsigned char * vari- + able. + + PCRE_INFO_LASTLITERAL + + Return the value of the rightmost literal byte that must exist in any + matched string, other than at its start, if such a byte has been + recorded. The fourth argument should point to an int variable. If there + is no such byte, -1 is returned. For anchored patterns, a last literal + byte is recorded only if it follows something of variable length. For + example, for the pattern /^a\d+z\d+/ the returned value is "z", but for + /^a\dz\d/ the returned value is -1. + + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE + + PCRE supports the use of named as well as numbered capturing parenthe- + ses. The names are just an additional way of identifying the parenthe- + ses, which still acquire a number. A caller that wants to extract data + from a named subpattern must convert the name to a number in order to + access the correct pointers in the output vector (described with + pcre_exec() below). In order to do this, it must first use these three + values to obtain the name-to-number mapping table for the pattern. + + The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT + gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size + of each entry; both of these return an int value. The entry size + depends on the length of the longest name. PCRE_INFO_NAMETABLE returns + a pointer to the first entry of the table (a pointer to char). The + first two bytes of each entry are the number of the capturing parenthe- + sis, most significant byte first. The rest of the entry is the corre- + sponding name, zero terminated. The names are in alphabetical order. + For example, consider the following pattern (assume PCRE_EXTENDED is + set, so white space - including newlines - is ignored): + + (?P<date> (?P<year>(\d\d)?\d\d) - + (?P<month>\d\d) - (?P<day>\d\d) ) + + There are four named subpatterns, so the table has four entries, and + each entry in the table is eight bytes long. The table is as follows, + with non-printing bytes shows in hex, and undefined bytes shown as ??: + + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? + + When writing code to extract data from named subpatterns, remember that + the length of each entry may be different for each compiled pattern. + + PCRE_INFO_OPTIONS + + Return a copy of the options with which the pattern was compiled. The + fourth argument should point to an unsigned long int variable. These + option bits are those specified in the call to pcre_compile(), modified + by any top-level option settings within the pattern itself. + + A pattern is automatically anchored by PCRE if all of its top-level + alternatives begin with one of the following: + + ^ unless PCRE_MULTILINE is set + \A always + \G always + .* if PCRE_DOTALL is set and there are no back + references to the subpattern in which .* appears + + For such patterns, the PCRE_ANCHORED bit is set in the options returned + by pcre_fullinfo(). + + PCRE_INFO_SIZE + + Return the size of the compiled pattern, that is, the value that was + passed as the argument to pcre_malloc() when PCRE was getting memory in + which to place the compiled data. The fourth argument should point to a + size_t variable. + + PCRE_INFO_STUDYSIZE + + Returns the size of the data block pointed to by the study_data field + in a pcre_extra block. That is, it is the value that was passed to + pcre_malloc() when PCRE was getting memory into which to place the data + created by pcre_study(). The fourth argument should point to a size_t + variable. + + +OBSOLETE INFO FUNCTION + + int pcre_info(const pcre *code, int *optptr, int *firstcharptr); + + The pcre_info() function is now obsolete because its interface is too + restrictive to return all the available data about a compiled pattern. + New programs should use pcre_fullinfo() instead. The yield of + pcre_info() is the number of capturing subpatterns, or one of the fol- + lowing negative numbers: + + PCRE_ERROR_NULL the argument code was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + + If the optptr argument is not NULL, a copy of the options with which + the pattern was compiled is placed in the integer it points to (see + PCRE_INFO_OPTIONS above). + + If the pattern is not anchored and the firstcharptr argument is not + NULL, it is used to pass back information about the first character of + any matched string (see PCRE_INFO_FIRSTBYTE above). + + +MATCHING A PATTERN + + int pcre_exec(const pcre *code, const pcre_extra *extra, + const char *subject, int length, int startoffset, + int options, int *ovector, int ovecsize); + + The function pcre_exec() is called to match a subject string against a + pre-compiled pattern, which is passed in the code argument. If the pat- + tern has been studied, the result of the study should be passed in the + extra argument. + + Here is an example of a simple call to pcre_exec(): + + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector for substring information */ + 30); /* number of elements in the vector */ + + If the extra argument is not NULL, it must point to a pcre_extra data + block. The pcre_study() function returns such a block (when it doesn't + return NULL), but you can also create one for yourself, and pass addi- + tional information in it. The fields in the block are as follows: + + unsigned long int flags; + void *study_data; + unsigned long int match_limit; + void *callout_data; + + The flags field is a bitmap that specifies which of the other fields + are set. The flag bits are: + + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_CALLOUT_DATA + + Other flag bits should be set to zero. The study_data field is set in + the pcre_extra block that is returned by pcre_study(), together with + the appropriate flag bit. You should not set this yourself, but you can + add to the block by setting the other fields. + + The match_limit field provides a means of preventing PCRE from using up + a vast amount of resources when running patterns that are not going to + match, but which have a very large number of possibilities in their + search trees. The classic example is the use of nested unlimited + repeats. Internally, PCRE uses a function called match() which it calls + repeatedly (sometimes recursively). The limit is imposed on the number + of times this function is called during a match, which has the effect + of limiting the amount of recursion and backtracking that can take + place. For patterns that are not anchored, the count starts from zero + for each position in the subject string. + + The default limit for the library can be set when PCRE is built; the + default default is 10 million, which handles all but the most extreme + cases. You can reduce the default by suppling pcre_exec() with a + pcre_extra block in which match_limit is set to a smaller value, and + PCRE_EXTRA_MATCH_LIMIT is set in the flags field. If the limit is + exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT. + + The pcre_callout field is used in conjunction with the "callout" fea- + ture, which is described in the pcrecallout documentation. + + The PCRE_ANCHORED option can be passed in the options argument, whose + unused bits must be zero. This limits pcre_exec() to matching at the + first matching position. However, if a pattern was compiled with + PCRE_ANCHORED, or turned out to be anchored by virtue of its contents, + it cannot be made unachored at matching time. + + When PCRE_UTF8 was set at compile time, the validity of the subject as + a UTF-8 string is automatically checked, and the value of startoffset + is also checked to ensure that it points to the start of a UTF-8 char- + acter. If an invalid UTF-8 sequence of bytes is found, pcre_exec() + returns the error PCRE_ERROR_BADUTF8. If startoffset contains an + invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned. + + If you already know that your subject is valid, and you want to skip + these checks for performance reasons, you can set the + PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might want to + do this for the second and subsequent calls to pcre_exec() if you are + making repeated calls to find all the matches in a single subject + string. However, you should be sure that the value of startoffset + points to the start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is + set, the effect of passing an invalid UTF-8 string as a subject, or a + value of startoffset that does not point to the start of a UTF-8 char- + acter, is undefined. Your program may crash. + + There are also three further options that can be set only at matching + time: + + PCRE_NOTBOL + + The first character of the string is not the beginning of a line, so + the circumflex metacharacter should not match before it. Setting this + without PCRE_MULTILINE (at compile time) causes circumflex never to + match. + + PCRE_NOTEOL + + The end of the string is not the end of a line, so the dollar metachar- + acter should not match it nor (except in multiline mode) a newline + immediately before it. Setting this without PCRE_MULTILINE (at compile + time) causes dollar never to match. + + PCRE_NOTEMPTY + + An empty string is not considered to be a valid match if this option is + set. If there are alternatives in the pattern, they are tried. If all + the alternatives match the empty string, the entire match fails. For + example, if the pattern + + a?b? + + is applied to a string not beginning with "a" or "b", it matches the + empty string at the start of the subject. With PCRE_NOTEMPTY set, this + match is not valid, so PCRE searches further into the string for occur- + rences of "a" or "b". + + Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe- + cial case of a pattern match of the empty string within its split() + function, and when using the /g modifier. It is possible to emulate + Perl's behaviour after matching a null string by first trying the match + again at the same offset with PCRE_NOTEMPTY set, and then if that fails + by advancing the starting offset (see below) and trying an ordinary + match again. + + The subject string is passed to pcre_exec() as a pointer in subject, a + length in length, and a starting byte offset in startoffset. Unlike the + pattern string, the subject may contain binary zero bytes. When the + starting offset is zero, the search for a match starts at the beginning + of the subject, and this is by far the most common case. + + If the pattern was compiled with the PCRE_UTF8 option, the subject must + be a sequence of bytes that is a valid UTF-8 string, and the starting + offset must point to the beginning of a UTF-8 character. If an invalid + UTF-8 string or offset is passed, an error (either PCRE_ERROR_BADUTF8 + or PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option + PCRE_NO_UTF8_CHECK is set, in which case PCRE's behaviour is not + defined. + + A non-zero starting offset is useful when searching for another match + in the same subject by calling pcre_exec() again after a previous suc- + cess. Setting startoffset differs from just passing over a shortened + string and setting PCRE_NOTBOL in the case of a pattern that begins + with any kind of lookbehind. For example, consider the pattern + + \Biss\B + + which finds occurrences of "iss" in the middle of words. (\B matches + only if the current position in the subject is not a word boundary.) + When applied to the string "Mississipi" the first call to pcre_exec() + finds the first occurrence. If pcre_exec() is called again with just + the remainder of the subject, namely "issipi", it does not match, + because \B is always false at the start of the subject, which is deemed + to be a word boundary. However, if pcre_exec() is passed the entire + string again, but with startoffset set to 4, it finds the second + occurrence of "iss" because it is able to look behind the starting + point to discover that it is preceded by a letter. + + If a non-zero starting offset is passed when the pattern is anchored, + one attempt to match at the given offset is tried. This can only suc- + ceed if the pattern does not require the match to be at the start of + the subject. + + In general, a pattern matches a certain portion of the subject, and in + addition, further substrings from the subject may be picked out by + parts of the pattern. Following the usage in Jeffrey Friedl's book, + this is called "capturing" in what follows, and the phrase "capturing + subpattern" is used for a fragment of a pattern that picks out a sub- + string. PCRE supports several other kinds of parenthesized subpattern + that do not cause substrings to be captured. + + Captured substrings are returned to the caller via a vector of integer + offsets whose address is passed in ovector. The number of elements in + the vector is passed in ovecsize. The first two-thirds of the vector is + used to pass back captured substrings, each substring using a pair of + integers. The remaining third of the vector is used as workspace by + pcre_exec() while matching capturing subpatterns, and is not available + for passing back information. The length passed in ovecsize should + always be a multiple of three. If it is not, it is rounded down. + + When a match has been successful, information about captured substrings + is returned in pairs of integers, starting at the beginning of ovector, + and continuing up to two-thirds of its length at the most. The first + element of a pair is set to the offset of the first character in a sub- + string, and the second is set to the offset of the first character + after the end of a substring. The first pair, ovector[0] and ovec- + tor[1], identify the portion of the subject string matched by the + entire pattern. The next pair is used for the first capturing subpat- + tern, and so on. The value returned by pcre_exec() is the number of + pairs that have been set. If there are no capturing subpatterns, the + return value from a successful match is 1, indicating that just the + first pair of offsets has been set. + + Some convenience functions are provided for extracting the captured + substrings as separate strings. These are described in the following + section. + + It is possible for an capturing subpattern number n+1 to match some + part of the subject when subpattern n has not been used at all. For + example, if the string "abc" is matched against the pattern (a|(z))(bc) + subpatterns 1 and 3 are matched, but 2 is not. When this happens, both + offset values corresponding to the unused subpattern are set to -1. + + If a capturing subpattern is matched repeatedly, it is the last portion + of the string that it matched that gets returned. + + If the vector is too small to hold all the captured substrings, it is + used as far as possible (up to two-thirds of its length), and the func- + tion returns a value of zero. In particular, if the substring offsets + are not of interest, pcre_exec() may be called with ovector passed as + NULL and ovecsize as zero. However, if the pattern contains back refer- + ences and the ovector isn't big enough to remember the related sub- + strings, PCRE has to get additional memory for use during matching. + Thus it is usually advisable to supply an ovector. + + Note that pcre_info() can be used to find out how many capturing sub- + patterns there are in a compiled pattern. The smallest size for ovector + that will allow for n captured substrings, in addition to the offsets + of the substring matched by the whole pattern, is (n+1)*3. + + If pcre_exec() fails, it returns a negative number. The following are + defined in the header file: + + PCRE_ERROR_NOMATCH (-1) + + The subject string did not match the pattern. + + PCRE_ERROR_NULL (-2) + + Either code or subject was passed as NULL, or ovector was NULL and + ovecsize was not zero. + + PCRE_ERROR_BADOPTION (-3) + + An unrecognized bit was set in the options argument. + + PCRE_ERROR_BADMAGIC (-4) + + PCRE stores a 4-byte "magic number" at the start of the compiled code, + to catch the case when it is passed a junk pointer. This is the error + it gives when the magic number isn't present. + + PCRE_ERROR_UNKNOWN_NODE (-5) + + While running the pattern match, an unknown item was encountered in the + compiled pattern. This error could be caused by a bug in PCRE or by + overwriting of the compiled pattern. + + PCRE_ERROR_NOMEMORY (-6) + + If a pattern contains back references, but the ovector that is passed + to pcre_exec() is not big enough to remember the referenced substrings, + PCRE gets a block of memory at the start of matching to use for this + purpose. If the call via pcre_malloc() fails, this error is given. The + memory is freed at the end of matching. + + PCRE_ERROR_NOSUBSTRING (-7) + + This error is used by the pcre_copy_substring(), pcre_get_substring(), + and pcre_get_substring_list() functions (see below). It is never + returned by pcre_exec(). + + PCRE_ERROR_MATCHLIMIT (-8) + + The recursion and backtracking limit, as specified by the match_limit + field in a pcre_extra structure (or defaulted) was reached. See the + description above. + + PCRE_ERROR_CALLOUT (-9) + + This error is never generated by pcre_exec() itself. It is provided for + use by callout functions that want to yield a distinctive error code. + See the pcrecallout documentation for details. + + PCRE_ERROR_BADUTF8 (-10) + + A string that contains an invalid UTF-8 byte sequence was passed as a + subject. + + PCRE_ERROR_BADUTF8_OFFSET (-11) + + The UTF-8 byte sequence that was passed as a subject was valid, but the + value of startoffset did not point to the beginning of a UTF-8 charac- + ter. + + +EXTRACTING CAPTURED SUBSTRINGS BY NUMBER + + int pcre_copy_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, char *buffer, + int buffersize); + + int pcre_get_substring(const char *subject, int *ovector, + int stringcount, int stringnumber, + const char **stringptr); + + int pcre_get_substring_list(const char *subject, + int *ovector, int stringcount, const char ***listptr); + + Captured substrings can be accessed directly by using the offsets + returned by pcre_exec() in ovector. For convenience, the functions + pcre_copy_substring(), pcre_get_substring(), and pcre_get_sub- + string_list() are provided for extracting captured substrings as new, + separate, zero-terminated strings. These functions identify substrings + by number. The next section describes functions for extracting named + substrings. A substring that contains a binary zero is correctly + extracted and has a further zero added on the end, but the result is + not, of course, a C string. + + The first three arguments are the same for all three of these func- + tions: subject is the subject string which has just been successfully + matched, ovector is a pointer to the vector of integer offsets that was + passed to pcre_exec(), and stringcount is the number of substrings that + were captured by the match, including the substring that matched the + entire regular expression. This is the value returned by pcre_exec if + it is greater than zero. If pcre_exec() returned zero, indicating that + it ran out of space in ovector, the value passed as stringcount should + be the size of the vector divided by three. + + The functions pcre_copy_substring() and pcre_get_substring() extract a + single substring, whose number is given as stringnumber. A value of + zero extracts the substring that matched the entire pattern, while + higher values extract the captured substrings. For pcre_copy_sub- + string(), the string is placed in buffer, whose length is given by + buffersize, while for pcre_get_substring() a new block of memory is + obtained via pcre_malloc, and its address is returned via stringptr. + The yield of the function is the length of the string, not including + the terminating zero, or one of + + PCRE_ERROR_NOMEMORY (-6) + + The buffer was too small for pcre_copy_substring(), or the attempt to + get memory failed for pcre_get_substring(). + + PCRE_ERROR_NOSUBSTRING (-7) + + There is no substring whose number is stringnumber. + + The pcre_get_substring_list() function extracts all available sub- + strings and builds a list of pointers to them. All this is done in a + single block of memory which is obtained via pcre_malloc. The address + of the memory block is returned via listptr, which is also the start of + the list of string pointers. The end of the list is marked by a NULL + pointer. The yield of the function is zero if all went well, or + + PCRE_ERROR_NOMEMORY (-6) + + if the attempt to get the memory block failed. + + When any of these functions encounter a substring that is unset, which + can happen when capturing subpattern number n+1 matches some part of + the subject, but subpattern n has not been used at all, they return an + empty string. This can be distinguished from a genuine zero-length sub- + string by inspecting the appropriate offset in ovector, which is nega- + tive for unset substrings. + + The two convenience functions pcre_free_substring() and + pcre_free_substring_list() can be used to free the memory returned by a + previous call of pcre_get_substring() or pcre_get_substring_list(), + respectively. They do nothing more than call the function pointed to by + pcre_free, which of course could be called directly from a C program. + However, PCRE is used in some situations where it is linked via a spe- + cial interface to another programming language which cannot use + pcre_free directly; it is for these cases that the functions are pro- + vided. + + +EXTRACTING CAPTURED SUBSTRINGS BY NAME + + int pcre_copy_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + char *buffer, int buffersize); + + int pcre_get_stringnumber(const pcre *code, + const char *name); + + int pcre_get_named_substring(const pcre *code, + const char *subject, int *ovector, + int stringcount, const char *stringname, + const char **stringptr); + + To extract a substring by name, you first have to find associated num- + ber. This can be done by calling pcre_get_stringnumber(). The first + argument is the compiled pattern, and the second is the name. For exam- + ple, for this pattern + + ab(?<xxx>\d+)... + + the number of the subpattern called "xxx" is 1. Given the number, you + can then extract the substring directly, or use one of the functions + described in the previous section. For convenience, there are also two + functions that do the whole job. + + Most of the arguments of pcre_copy_named_substring() and + pcre_get_named_substring() are the same as those for the functions that + extract by number, and so are not re-described here. There are just two + differences. + + First, instead of a substring number, a substring name is given. Sec- + ond, there is an extra argument, given at the start, which is a pointer + to the compiled pattern. This is needed in order to gain access to the + name-to-number translation table. + + These functions call pcre_get_stringnumber(), and if it succeeds, they + then call pcre_copy_substring() or pcre_get_substring(), as appropri- + ate. + +Last updated: 09 December 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE CALLOUTS + + int (*pcre_callout)(pcre_callout_block *); + + PCRE provides a feature called "callout", which is a means of temporar- + ily passing control to the caller of PCRE in the middle of pattern + matching. The caller of PCRE provides an external function by putting + its entry point in the global variable pcre_callout. By default, this + variable contains NULL, which disables all calling out. + + Within a regular expression, (?C) indicates the points at which the + external function is to be called. Different callout points can be + identified by putting a number less than 256 after the letter C. The + default value is zero. For example, this pattern has two callout + points: + + (?C1)abc(?C2)def + + During matching, when PCRE reaches a callout point (and pcre_callout is + set), the external function is called. Its only argument is a pointer + to a pcre_callout block. This contains the following variables: + + int version; + int callout_number; + int *offset_vector; + const char *subject; + int subject_length; + int start_match; + int current_position; + int capture_top; + int capture_last; + void *callout_data; + + The version field is an integer containing the version number of the + block format. The current version is zero. The version number may + change in future if additional fields are added, but the intention is + never to remove any of the existing fields. + + The callout_number field contains the number of the callout, as com- + piled into the pattern (that is, the number after ?C). + + The offset_vector field is a pointer to the vector of offsets that was + passed by the caller to pcre_exec(). The contents can be inspected in + order to extract substrings that have been matched so far, in the same + way as for extracting substrings after a match has completed. + + The subject and subject_length fields contain copies the values that + were passed to pcre_exec(). + + The start_match field contains the offset within the subject at which + the current match attempt started. If the pattern is not anchored, the + callout function may be called several times for different starting + points. + + The current_position field contains the offset within the subject of + the current match pointer. + + The capture_top field contains one more than the number of the highest + numbered captured substring so far. If no substrings have been + captured, the value of capture_top is one. + + The capture_last field contains the number of the most recently cap- + tured substring. + + The callout_data field contains a value that is passed to pcre_exec() + by the caller specifically so that it can be passed back in callouts. + It is passed in the pcre_callout field of the pcre_extra data struc- + ture. If no such data was passed, the value of callout_data in a + pcre_callout block is NULL. There is a description of the pcre_extra + structure in the pcreapi documentation. + + + +RETURN VALUES + + The callout function returns an integer. If the value is zero, matching + proceeds as normal. If the value is greater than zero, matching fails + at the current point, but backtracking to test other possibilities goes + ahead, just as if a lookahead assertion had failed. If the value is + less than zero, the match is abandoned, and pcre_exec() returns the + value. + + Negative values should normally be chosen from the set of + PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan- + dard "no match" failure. The error number PCRE_ERROR_CALLOUT is + reserved for use by callout functions; it will never be used by PCRE + itself. + +Last updated: 21 January 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +DIFFERENCES FROM PERL + + This document describes the differences in the ways that PCRE and Perl + handle regular expressions. The differences described here are with + respect to Perl 5.8. + + 1. PCRE does not have full UTF-8 support. Details of what it does have + are given in the section on UTF-8 support in the main pcre page. + + 2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl + permits them, but they do not mean what you might think. For example, + (?!a){3} does not assert that the next three characters are not "a". It + just asserts that the next character is not "a" three times. + + 3. Capturing subpatterns that occur inside negative lookahead asser- + tions are counted, but their entries in the offsets vector are never + set. Perl sets its numerical variables from any such patterns that are + matched before the assertion fails to match something (thereby succeed- + ing), but only if the negative lookahead assertion contains just one + branch. + + 4. Though binary zero characters are supported in the subject string, + they are not allowed in a pattern string because it is passed as a nor- + mal C string, terminated by zero. The escape sequence "\0" can be used + in the pattern to represent a binary zero. + + 5. The following Perl escape sequences are not supported: \l, \u, \L, + \U, \P, \p, \N, and \X. In fact these are implemented by Perl's general + string-handling and are not part of its pattern matching engine. If any + of these are encountered by PCRE, an error is generated. + + 6. PCRE does support the \Q...\E escape for quoting substrings. Charac- + ters in between are treated as literals. This is slightly different + from Perl in that $ and @ are also handled as literals inside the + quotes. In Perl, they cause variable interpolation (but of course PCRE + does not have variables). Note the following examples: + + Pattern PCRE matches Perl matches + + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz + + The \Q...\E sequence is recognized both inside and outside character + classes. + + 7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) + constructions. However, there is some experimental support for recur- + sive patterns using the non-Perl items (?R), (?number) and (?P>name). + Also, the PCRE "callout" feature allows an external function to be + called during pattern matching. + + 8. There are some differences that are concerned with the settings of + captured strings when part of a pattern is repeated. For example, + matching "aba" against the pattern /^(a(b)?)+$/ in Perl leaves $2 + unset, but in PCRE it is set to "b". + + 9. PCRE provides some extensions to the Perl regular expression + facilities: + + (a) Although lookbehind assertions must match fixed length strings, + each alternative branch of a lookbehind assertion can match a different + length of string. Perl requires them all to have the same length. + + (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ + meta-character matches only at the very end of the string. + + (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe- + cial meaning is faulted. + + (d) If PCRE_UNGREEDY is set, the greediness of the repetition quanti- + fiers is inverted, that is, by default they are not greedy, but if fol- + lowed by a question mark they are. + + (e) PCRE_ANCHORED can be used to force a pattern to be tried only at + the first matching position in the subject string. + + (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP- + TURE options for pcre_exec() have no Perl equivalents. + + (g) The (?R), (?number), and (?P>name) constructs allows for recursive + pattern matching (Perl can do this using the (?p{code}) construct, + which PCRE cannot support.) + + (h) PCRE supports named capturing substrings, using the Python syntax. + + (i) PCRE supports the possessive quantifier "++" syntax, taken from + Sun's Java package. + + (j) The (R) condition, for testing recursion, is a PCRE extension. + + (k) The callout facility is PCRE-specific. + +Last updated: 09 December 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE REGULAR EXPRESSION DETAILS + + The syntax and semantics of the regular expressions supported by PCRE + are described below. Regular expressions are also described in the Perl + documentation and in a number of other books, some of which have copi- + ous examples. Jeffrey Friedl's "Mastering Regular Expressions", pub- + lished by O'Reilly, covers them in great detail. The description here + is intended as reference documentation. + + The basic operation of PCRE is on strings of bytes. However, there is + also support for UTF-8 character strings. To use this support you must + build PCRE to include UTF-8 support, and then call pcre_compile() with + the PCRE_UTF8 option. How this affects the pattern matching is men- + tioned in several places below. There is also a summary of UTF-8 fea- + tures in the section on UTF-8 support in the main pcre page. + + A regular expression is a pattern that is matched against a subject + string from left to right. Most characters stand for themselves in a + pattern, and match the corresponding characters in the subject. As a + trivial example, the pattern + + The quick brown fox + + matches a portion of a subject string that is identical to itself. The + power of regular expressions comes from the ability to include alterna- + tives and repetitions in the pattern. These are encoded in the pattern + by the use of meta-characters, which do not stand for themselves but + instead are interpreted in some special way. + + There are two different sets of meta-characters: those that are recog- + nized anywhere in the pattern except within square brackets, and those + that are recognized in square brackets. Outside square brackets, the + meta-characters are as follows: + + \ general escape character with several uses + ^ assert start of string (or line, in multiline mode) + $ assert end of string (or line, in multiline mode) + . match any character except newline (by default) + [ start character class definition + | start of alternative branch + ( start subpattern + ) end subpattern + ? extends the meaning of ( + also 0 or 1 quantifier + also quantifier minimizer + * 0 or more quantifier + + 1 or more quantifier + also "possessive quantifier" + { start min/max quantifier + + Part of a pattern that is in square brackets is called a "character + class". In a character class the only meta-characters are: + + \ general escape character + ^ negate the class, but only if the first character + - indicates character range + [ POSIX character class (only if followed by POSIX + syntax) + ] terminates the character class + + The following sections describe the use of each of the meta-characters. + + +BACKSLASH + + The backslash character has several uses. Firstly, if it is followed by + a non-alphameric character, it takes away any special meaning that + character may have. This use of backslash as an escape character + applies both inside and outside character classes. + + For example, if you want to match a * character, you write \* in the + pattern. This escaping action applies whether or not the following + character would otherwise be interpreted as a meta-character, so it is + always safe to precede a non-alphameric with backslash to specify that + it stands for itself. In particular, if you want to match a backslash, + you write \\. + + If a pattern is compiled with the PCRE_EXTENDED option, whitespace in + the pattern (other than in a character class) and characters between a + # outside a character class and the next newline character are ignored. + An escaping backslash can be used to include a whitespace or # charac- + ter as part of the pattern. + + If you want to remove the special meaning from a sequence of charac- + ters, you can do so by putting them between \Q and \E. This is differ- + ent from Perl in that $ and @ are handled as literals in \Q...\E + sequences in PCRE, whereas in Perl, $ and @ cause variable interpola- + tion. Note the following examples: + + Pattern PCRE matches Perl matches + + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz + + The \Q...\E sequence is recognized both inside and outside character + classes. + + A second use of backslash provides a way of encoding non-printing char- + acters in patterns in a visible manner. There is no restriction on the + appearance of non-printing characters, apart from the binary zero that + terminates a pattern, but when a pattern is being prepared by text + editing, it is usually easier to use one of the following escape + sequences than the binary character it represents: + + \a alarm, that is, the BEL character (hex 07) + \cx "control-x", where x is any character + \e escape (hex 1B) + \f formfeed (hex 0C) + \n newline (hex 0A) + \r carriage return (hex 0D) + \t tab (hex 09) + \ddd character with octal code ddd, or backreference + \xhh character with hex code hh + \x{hhh..} character with hex code hhh... (UTF-8 mode only) + + The precise effect of \cx is as follows: if x is a lower case letter, + it is converted to upper case. Then bit 6 of the character (hex 40) is + inverted. Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c; + becomes hex 7B. + + After \x, from zero to two hexadecimal digits are read (letters can be + in upper or lower case). In UTF-8 mode, any number of hexadecimal dig- + its may appear between \x{ and }, but the value of the character code + must be less than 2**31 (that is, the maximum hexadecimal value is + 7FFFFFFF). If characters other than hexadecimal digits appear between + \x{ and }, or if there is no terminating }, this form of escape is not + recognized. Instead, the initial \x will be interpreted as a basic hex- + adecimal escape, with no following digits, giving a byte whose value is + zero. + + Characters whose value is less than 256 can be defined by either of the + two syntaxes for \x when PCRE is in UTF-8 mode. There is no difference + in the way they are handled. For example, \xdc is exactly the same as + \x{dc}. + + After \0 up to two further octal digits are read. In both cases, if + there are fewer than two digits, just those that are present are used. + Thus the sequence \0\x\07 specifies two binary zeros followed by a BEL + character (code value 7). Make sure you supply two digits after the + initial zero if the character that follows is itself an octal digit. + + The handling of a backslash followed by a digit other than 0 is compli- + cated. Outside a character class, PCRE reads it and any following dig- + its as a decimal number. If the number is less than 10, or if there + have been at least that many previous capturing left parentheses in the + expression, the entire sequence is taken as a back reference. A + description of how this works is given later, following the discussion + of parenthesized subpatterns. + + Inside a character class, or if the decimal number is greater than 9 + and there have not been that many capturing subpatterns, PCRE re-reads + up to three octal digits following the backslash, and generates a sin- + gle byte from the least significant 8 bits of the value. Any subsequent + digits stand for themselves. For example: + + \040 is another way of writing a space + \40 is the same, provided there are fewer than 40 + previous capturing subpatterns + \7 is always a back reference + \11 might be a back reference, or another way of + writing a tab + \011 is always a tab + \0113 is a tab followed by the character "3" + \113 might be a back reference, otherwise the + character with octal code 113 + \377 might be a back reference, otherwise + the byte consisting entirely of 1 bits + \81 is either a back reference, or a binary zero + followed by the two characters "8" and "1" + + Note that octal values of 100 or greater must not be introduced by a + leading zero, because no more than three octal digits are ever read. + + All the sequences that define a single byte value or a single UTF-8 + character (in UTF-8 mode) can be used both inside and outside character + classes. In addition, inside a character class, the sequence \b is + interpreted as the backspace character (hex 08). Outside a character + class it has a different meaning (see below). + + The third use of backslash is for specifying generic character types: + + \d any decimal digit + \D any character that is not a decimal digit + \s any whitespace character + \S any character that is not a whitespace character + \w any "word" character + \W any "non-word" character + + Each pair of escape sequences partitions the complete set of characters + into two disjoint sets. Any given character matches one, and only one, + of each pair. + + In UTF-8 mode, characters with values greater than 255 never match \d, + \s, or \w, and always match \D, \S, and \W. + + For compatibility with Perl, \s does not match the VT character (code + 11). This makes it different from the the POSIX "space" class. The \s + characters are HT (9), LF (10), FF (12), CR (13), and space (32). + + A "word" character is any letter or digit or the underscore character, + that is, any character which can be part of a Perl "word". The defini- + tion of letters and digits is controlled by PCRE's character tables, + and may vary if locale- specific matching is taking place (see "Locale + support" in the pcreapi page). For example, in the "fr" (French) + locale, some character codes greater than 128 are used for accented + letters, and these are matched by \w. + + These character type sequences can appear both inside and outside char- + acter classes. They each match one character of the appropriate type. + If the current matching point is at the end of the subject string, all + of them fail, since there is no character to match. + + The fourth use of backslash is for certain simple assertions. An asser- + tion specifies a condition that has to be met at a particular point in + a match, without consuming any characters from the subject string. The + use of subpatterns for more complicated assertions is described below. + The backslashed assertions are + + \b matches at a word boundary + \B matches when not at a word boundary + \A matches at start of subject + \Z matches at end of subject or before newline at end + \z matches at end of subject + \G matches at first matching position in subject + + These assertions may not appear in character classes (but note that \b + has a different meaning, namely the backspace character, inside a char- + acter class). + + A word boundary is a position in the subject string where the current + character and the previous character do not both match \w or \W (i.e. + one matches \w and the other matches \W), or the start or end of the + string if the first or last character matches \w, respectively. + + The \A, \Z, and \z assertions differ from the traditional circumflex + and dollar (described below) in that they only ever match at the very + start and end of the subject string, whatever options are set. Thus, + they are independent of multiline mode. + + They are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options. If the + startoffset argument of pcre_exec() is non-zero, indicating that match- + ing is to start at a point other than the beginning of the subject, \A + can never match. The difference between \Z and \z is that \Z matches + before a newline that is the last character of the string as well as at + the end of the string, whereas \z matches only at the end. + + The \G assertion is true only when the current matching position is at + the start point of the match, as specified by the startoffset argument + of pcre_exec(). It differs from \A when the value of startoffset is + non-zero. By calling pcre_exec() multiple times with appropriate argu- + ments, you can mimic Perl's /g option, and it is in this kind of imple- + mentation where \G can be useful. + + Note, however, that PCRE's interpretation of \G, as the start of the + current match, is subtly different from Perl's, which defines it as the + end of the previous match. In Perl, these can be different when the + previously matched string was empty. Because PCRE does just one match + at a time, it cannot reproduce this behaviour. + + If all the alternatives of a pattern begin with \G, the expression is + anchored to the starting match position, and the "anchored" flag is set + in the compiled regular expression. + + +CIRCUMFLEX AND DOLLAR + + Outside a character class, in the default matching mode, the circumflex + character is an assertion which is true only if the current matching + point is at the start of the subject string. If the startoffset argu- + ment of pcre_exec() is non-zero, circumflex can never match if the + PCRE_MULTILINE option is unset. Inside a character class, circumflex + has an entirely different meaning (see below). + + Circumflex need not be the first character of the pattern if a number + of alternatives are involved, but it should be the first thing in each + alternative in which it appears if the pattern is ever to match that + branch. If all possible alternatives start with a circumflex, that is, + if the pattern is constrained to match only at the start of the sub- + ject, it is said to be an "anchored" pattern. (There are also other + constructs that can cause a pattern to be anchored.) + + A dollar character is an assertion which is true only if the current + matching point is at the end of the subject string, or immediately + before a newline character that is the last character in the string (by + default). Dollar need not be the last character of the pattern if a + number of alternatives are involved, but it should be the last item in + any branch in which it appears. Dollar has no special meaning in a + character class. + + The meaning of dollar can be changed so that it matches only at the + very end of the string, by setting the PCRE_DOLLAR_ENDONLY option at + compile time. This does not affect the \Z assertion. + + The meanings of the circumflex and dollar characters are changed if the + PCRE_MULTILINE option is set. When this is the case, they match immedi- + ately after and immediately before an internal newline character, + respectively, in addition to matching at the start and end of the sub- + ject string. For example, the pattern /^abc$/ matches the subject + string "def\nabc" in multiline mode, but not otherwise. Consequently, + patterns that are anchored in single line mode because all branches + start with ^ are not anchored in multiline mode, and a match for cir- + cumflex is possible when the startoffset argument of pcre_exec() is + non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE + is set. + + Note that the sequences \A, \Z, and \z can be used to match the start + and end of the subject in both modes, and if all branches of a pattern + start with \A it is always anchored, whether PCRE_MULTILINE is set or + not. + + +FULL STOP (PERIOD, DOT) + + Outside a character class, a dot in the pattern matches any one charac- + ter in the subject, including a non-printing character, but not (by + default) newline. In UTF-8 mode, a dot matches any UTF-8 character, + which might be more than one byte long, except (by default) for new- + line. If the PCRE_DOTALL option is set, dots match newlines as well. + The handling of dot is entirely independent of the handling of circum- + flex and dollar, the only relationship being that they both involve + newline characters. Dot has no special meaning in a character class. + + +MATCHING A SINGLE BYTE + + Outside a character class, the escape sequence \C matches any one byte, + both in and out of UTF-8 mode. Unlike a dot, it always matches a new- + line. The feature is provided in Perl in order to match individual + bytes in UTF-8 mode. Because it breaks up UTF-8 characters into indi- + vidual bytes, what remains in the string may be a malformed UTF-8 + string. For this reason it is best avoided. + + PCRE does not allow \C to appear in lookbehind assertions (see below), + because in UTF-8 mode it makes it impossible to calculate the length of + the lookbehind. + + +SQUARE BRACKETS + + An opening square bracket introduces a character class, terminated by a + closing square bracket. A closing square bracket on its own is not spe- + cial. If a closing square bracket is required as a member of the class, + it should be the first data character in the class (after an initial + circumflex, if present) or escaped with a backslash. + + A character class matches a single character in the subject. In UTF-8 + mode, the character may occupy more than one byte. A matched character + must be in the set of characters defined by the class, unless the first + character in the class definition is a circumflex, in which case the + subject character must not be in the set defined by the class. If a + circumflex is actually required as a member of the class, ensure it is + not the first character, or escape it with a backslash. + + For example, the character class [aeiou] matches any lower case vowel, + while [^aeiou] matches any character that is not a lower case vowel. + Note that a circumflex is just a convenient notation for specifying the + characters which are in the class by enumerating those that are not. It + is not an assertion: it still consumes a character from the subject + string, and fails if the current pointer is at the end of the string. + + In UTF-8 mode, characters with values greater than 255 can be included + in a class as a literal string of bytes, or by using the \x{ escaping + mechanism. + + When caseless matching is set, any letters in a class represent both + their upper case and lower case versions, so for example, a caseless + [aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not + match "A", whereas a caseful version would. PCRE does not support the + concept of case for characters with values greater than 255. + + The newline character is never treated in any special way in character + classes, whatever the setting of the PCRE_DOTALL or PCRE_MULTILINE + options is. A class such as [^a] will always match a newline. + + The minus (hyphen) character can be used to specify a range of charac- + ters in a character class. For example, [d-m] matches any letter + between d and m, inclusive. If a minus character is required in a + class, it must be escaped with a backslash or appear in a position + where it cannot be interpreted as indicating a range, typically as the + first or last character in the class. + + It is not possible to have the literal character "]" as the end charac- + ter of a range. A pattern such as [W-]46] is interpreted as a class of + two characters ("W" and "-") followed by a literal string "46]", so it + would match "W46]" or "-46]". However, if the "]" is escaped with a + backslash it is interpreted as the end of range, so [W-\]46] is inter- + preted as a single class containing a range followed by two separate + characters. The octal or hexadecimal representation of "]" can also be + used to end a range. + + Ranges operate in the collating sequence of character values. They can + also be used for characters specified numerically, for example + [\000-\037]. In UTF-8 mode, ranges can include characters whose values + are greater than 255, for example [\x{100}-\x{2ff}]. + + If a range that includes letters is used when caseless matching is set, + it matches the letters in either case. For example, [W-c] is equivalent + to [][\^_`wxyzabc], matched caselessly, and if character tables for the + "fr" locale are in use, [\xc8-\xcb] matches accented E characters in + both cases. + + The character types \d, \D, \s, \S, \w, and \W may also appear in a + character class, and add the characters that they match to the class. + For example, [\dABCDEF] matches any hexadecimal digit. A circumflex can + conveniently be used with the upper case character types to specify a + more restricted set of characters than the matching lower case type. + For example, the class [^\W_] matches any letter or digit, but not + underscore. + + All non-alphameric characters other than \, -, ^ (at the start) and the + terminating ] are non-special in character classes, but it does no harm + if they are escaped. + + +POSIX CHARACTER CLASSES + + Perl supports the POSIX notation for character classes, which uses + names enclosed by [: and :] within the enclosing square brackets. PCRE + also supports this notation. For example, + + [01[:alpha:]%] + + matches "0", "1", any alphabetic character, or "%". The supported class + names are + + alnum letters and digits + alpha letters + ascii character codes 0 - 127 + blank space or tab only + cntrl control characters + digit decimal digits (same as \d) + graph printing characters, excluding space + lower lower case letters + print printing characters, including space + punct printing characters, excluding letters and digits + space white space (not quite the same as \s) + upper upper case letters + word "word" characters (same as \w) + xdigit hexadecimal digits + + The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), + and space (32). Notice that this list includes the VT character (code + 11). This makes "space" different to \s, which does not include VT (for + Perl compatibility). + + The name "word" is a Perl extension, and "blank" is a GNU extension + from Perl 5.8. Another Perl extension is negation, which is indicated + by a ^ character after the colon. For example, + + [12[:^digit:]] + + matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the + POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but + these are not supported, and an error is given if they are encountered. + + In UTF-8 mode, characters with values greater than 255 do not match any + of the POSIX character classes. + + +VERTICAL BAR + + Vertical bar characters are used to separate alternative patterns. For + example, the pattern + + gilbert|sullivan + + matches either "gilbert" or "sullivan". Any number of alternatives may + appear, and an empty alternative is permitted (matching the empty + string). The matching process tries each alternative in turn, from + left to right, and the first one that succeeds is used. If the alterna- + tives are within a subpattern (defined below), "succeeds" means match- + ing the rest of the main pattern as well as the alternative in the sub- + pattern. + + +INTERNAL OPTION SETTING + + The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and + PCRE_EXTENDED options can be changed from within the pattern by a + sequence of Perl option letters enclosed between "(?" and ")". The + option letters are + + i for PCRE_CASELESS + m for PCRE_MULTILINE + s for PCRE_DOTALL + x for PCRE_EXTENDED + + For example, (?im) sets caseless, multiline matching. It is also possi- + ble to unset these options by preceding the letter with a hyphen, and a + combined setting and unsetting such as (?im-sx), which sets PCRE_CASE- + LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, + is also permitted. If a letter appears both before and after the + hyphen, the option is unset. + + When an option change occurs at top level (that is, not inside subpat- + tern parentheses), the change applies to the remainder of the pattern + that follows. If the change is placed right at the start of a pattern, + PCRE extracts it into the global options (and it will therefore show up + in data extracted by the pcre_fullinfo() function). + + An option change within a subpattern affects only that part of the cur- + rent pattern that follows it, so + + (a(?i)b)c + + matches abc and aBc and no other strings (assuming PCRE_CASELESS is not + used). By this means, options can be made to have different settings + in different parts of the pattern. Any changes made in one alternative + do carry on into subsequent branches within the same subpattern. For + example, + + (a(?i)b|c) + + matches "ab", "aB", "c", and "C", even though when matching "C" the + first branch is abandoned before the option setting. This is because + the effects of option settings happen at compile time. There would be + some very weird behaviour otherwise. + + The PCRE-specific options PCRE_UNGREEDY and PCRE_EXTRA can be changed + in the same way as the Perl-compatible options by using the characters + U and X respectively. The (?X) flag setting is special in that it must + always occur earlier in the pattern than any of the additional features + it turns on, even when it is at top level. It is best put at the start. + + +SUBPATTERNS + + Subpatterns are delimited by parentheses (round brackets), which can be + nested. Marking part of a pattern as a subpattern does two things: + + 1. It localizes a set of alternatives. For example, the pattern + + cat(aract|erpillar|) + + matches one of the words "cat", "cataract", or "caterpillar". Without + the parentheses, it would match "cataract", "erpillar" or the empty + string. + + 2. It sets up the subpattern as a capturing subpattern (as defined + above). When the whole pattern matches, that portion of the subject + string that matched the subpattern is passed back to the caller via the + ovector argument of pcre_exec(). Opening parentheses are counted from + left to right (starting from 1) to obtain the numbers of the capturing + subpatterns. + + For example, if the string "the red king" is matched against the pat- + tern + + the ((red|white) (king|queen)) + + the captured substrings are "red king", "red", and "king", and are num- + bered 1, 2, and 3, respectively. + + The fact that plain parentheses fulfil two functions is not always + helpful. There are often times when a grouping subpattern is required + without a capturing requirement. If an opening parenthesis is followed + by a question mark and a colon, the subpattern does not do any captur- + ing, and is not counted when computing the number of any subsequent + capturing subpatterns. For example, if the string "the white queen" is + matched against the pattern + + the ((?:red|white) (king|queen)) + + the captured substrings are "white queen" and "queen", and are numbered + 1 and 2. The maximum number of capturing subpatterns is 65535, and the + maximum depth of nesting of all subpatterns, both capturing and non- + capturing, is 200. + + As a convenient shorthand, if any option settings are required at the + start of a non-capturing subpattern, the option letters may appear + between the "?" and the ":". Thus the two patterns + + (?i:saturday|sunday) + (?:(?i)saturday|sunday) + + match exactly the same set of strings. Because alternative branches are + tried from left to right, and options are not reset until the end of + the subpattern is reached, an option setting in one branch does affect + subsequent branches, so the above patterns match "SUNDAY" as well as + "Saturday". + + +NAMED SUBPATTERNS + + Identifying capturing parentheses by number is simple, but it can be + very hard to keep track of the numbers in complicated regular expres- + sions. Furthermore, if an expression is modified, the numbers may + change. To help with the difficulty, PCRE supports the naming of sub- + patterns, something that Perl does not provide. The Python syntax + (?P<name>...) is used. Names consist of alphanumeric characters and + underscores, and must be unique within a pattern. + + Named capturing parentheses are still allocated numbers as well as + names. The PCRE API provides function calls for extracting the name-to- + number translation table from a compiled pattern. For further details + see the pcreapi documentation. + + +REPETITION + + Repetition is specified by quantifiers, which can follow any of the + following items: + + a literal data character + the . metacharacter + the \C escape sequence + escapes such as \d that match single characters + a character class + a back reference (see next section) + a parenthesized subpattern (unless it is an assertion) + + The general repetition quantifier specifies a minimum and maximum num- + ber of permitted matches, by giving the two numbers in curly brackets + (braces), separated by a comma. The numbers must be less than 65536, + and the first must be less than or equal to the second. For example: + + z{2,4} + + matches "zz", "zzz", or "zzzz". A closing brace on its own is not a + special character. If the second number is omitted, but the comma is + present, there is no upper limit; if the second number and the comma + are both omitted, the quantifier specifies an exact number of required + matches. Thus + + [aeiou]{3,} + + matches at least 3 successive vowels, but may match many more, while + + \d{8} + + matches exactly 8 digits. An opening curly bracket that appears in a + position where a quantifier is not allowed, or one that does not match + the syntax of a quantifier, is taken as a literal character. For exam- + ple, {,6} is not a quantifier, but a literal string of four characters. + + In UTF-8 mode, quantifiers apply to UTF-8 characters rather than to + individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char- + acters, each of which is represented by a two-byte sequence. + + The quantifier {0} is permitted, causing the expression to behave as if + the previous item and the quantifier were not present. + + For convenience (and historical compatibility) the three most common + quantifiers have single-character abbreviations: + + * is equivalent to {0,} + + is equivalent to {1,} + ? is equivalent to {0,1} + + It is possible to construct infinite loops by following a subpattern + that can match no characters with a quantifier that has no upper limit, + for example: + + (a?)* + + Earlier versions of Perl and PCRE used to give an error at compile time + for such patterns. However, because there are cases where this can be + useful, such patterns are now accepted, but if any repetition of the + subpattern does in fact match no characters, the loop is forcibly bro- + ken. + + By default, the quantifiers are "greedy", that is, they match as much + as possible (up to the maximum number of permitted times), without + causing the rest of the pattern to fail. The classic example of where + this gives problems is in trying to match comments in C programs. These + appear between the sequences /* and */ and within the sequence, indi- + vidual * and / characters may appear. An attempt to match C comments by + applying the pattern + + /\*.*\*/ + + to the string + + /* first command */ not comment /* second comment */ + + fails, because it matches the entire string owing to the greediness of + the .* item. + + However, if a quantifier is followed by a question mark, it ceases to + be greedy, and instead matches the minimum number of times possible, so + the pattern + + /\*.*?\*/ + + does the right thing with the C comments. The meaning of the various + quantifiers is not otherwise changed, just the preferred number of + matches. Do not confuse this use of question mark with its use as a + quantifier in its own right. Because it has two uses, it can sometimes + appear doubled, as in + + \d??\d + + which matches one digit by preference, but can match two if that is the + only way the rest of the pattern matches. + + If the PCRE_UNGREEDY option is set (an option which is not available in + Perl), the quantifiers are not greedy by default, but individual ones + can be made greedy by following them with a question mark. In other + words, it inverts the default behaviour. + + When a parenthesized subpattern is quantified with a minimum repeat + count that is greater than 1 or with a limited maximum, more store is + required for the compiled pattern, in proportion to the size of the + minimum or maximum. + + If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv- + alent to Perl's /s) is set, thus allowing the . to match newlines, the + pattern is implicitly anchored, because whatever follows will be tried + against every character position in the subject string, so there is no + point in retrying the overall match at any position after the first. + PCRE normally treats such a pattern as though it were preceded by \A. + + In cases where it is known that the subject string contains no new- + lines, it is worth setting PCRE_DOTALL in order to obtain this opti- + mization, or alternatively using ^ to indicate anchoring explicitly. + + However, there is one situation where the optimization cannot be used. + When .* is inside capturing parentheses that are the subject of a + backreference elsewhere in the pattern, a match at the start may fail, + and a later one succeed. Consider, for example: + + (.*)abc\1 + + If the subject is "xyz123abc123" the match point is the fourth charac- + ter. For this reason, such a pattern is not implicitly anchored. + + When a capturing subpattern is repeated, the value captured is the sub- + string that matched the final iteration. For example, after + + (tweedle[dume]{3}\s*)+ + + has matched "tweedledum tweedledee" the value of the captured substring + is "tweedledee". However, if there are nested capturing subpatterns, + the corresponding captured values may have been set in previous itera- + tions. For example, after + + /(a|(b))+/ + + matches "aba" the value of the second captured substring is "b". + + +ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS + + With both maximizing and minimizing repetition, failure of what follows + normally causes the repeated item to be re-evaluated to see if a dif- + ferent number of repeats allows the rest of the pattern to match. Some- + times it is useful to prevent this, either to change the nature of the + match, or to cause it fail earlier than it otherwise might, when the + author of the pattern knows there is no point in carrying on. + + Consider, for example, the pattern \d+foo when applied to the subject + line + + 123456bar + + After matching all 6 digits and then failing to match "foo", the normal + action of the matcher is to try again with only 5 digits matching the + \d+ item, and then with 4, and so on, before ultimately failing. + "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides + the means for specifying that once a subpattern has matched, it is not + to be re-evaluated in this way. + + If we use atomic grouping for the previous example, the matcher would + give up immediately on failing to match "foo" the first time. The nota- + tion is a kind of special parenthesis, starting with (?> as in this + example: + + (?>\d+)foo + + This kind of parenthesis "locks up" the part of the pattern it con- + tains once it has matched, and a failure further into the pattern is + prevented from backtracking into it. Backtracking past it to previous + items, however, works as normal. + + An alternative description is that a subpattern of this type matches + the string of characters that an identical standalone pattern would + match, if anchored at the current point in the subject string. + + Atomic grouping subpatterns are not capturing subpatterns. Simple cases + such as the above example can be thought of as a maximizing repeat that + must swallow everything it can. So, while both \d+ and \d+? are pre- + pared to adjust the number of digits they match in order to make the + rest of the pattern match, (?>\d+) can only match an entire sequence of + digits. + + Atomic groups in general can of course contain arbitrarily complicated + subpatterns, and can be nested. However, when the subpattern for an + atomic group is just a single repeated item, as in the example above, a + simpler notation, called a "possessive quantifier" can be used. This + consists of an additional + character following a quantifier. Using + this notation, the previous example can be rewritten as + + \d++bar + + Possessive quantifiers are always greedy; the setting of the + PCRE_UNGREEDY option is ignored. They are a convenient notation for the + simpler forms of atomic group. However, there is no difference in the + meaning or processing of a possessive quantifier and the equivalent + atomic group. + + The possessive quantifier syntax is an extension to the Perl syntax. It + originates in Sun's Java package. + + When a pattern contains an unlimited repeat inside a subpattern that + can itself be repeated an unlimited number of times, the use of an + atomic group is the only way to avoid some failing matches taking a + very long time indeed. The pattern + + (\D+|<\d+>)*[!?] + + matches an unlimited number of substrings that either consist of non- + digits, or digits enclosed in <>, followed by either ! or ?. When it + matches, it runs quickly. However, if it is applied to + + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + + it takes a long time before reporting failure. This is because the + string can be divided between the two repeats in a large number of + ways, and all have to be tried. (The example used [!?] rather than a + single character at the end, because both PCRE and Perl have an opti- + mization that allows for fast failure when a single character is used. + They remember the last single character that is required for a match, + and fail early if it is not present in the string.) If the pattern is + changed to + + ((?>\D+)|<\d+>)*[!?] + + sequences of non-digits cannot be broken, and failure happens quickly. + + +BACK REFERENCES + + Outside a character class, a backslash followed by a digit greater than + 0 (and possibly further digits) is a back reference to a capturing sub- + pattern earlier (that is, to its left) in the pattern, provided there + have been that many previous capturing left parentheses. + + However, if the decimal number following the backslash is less than 10, + it is always taken as a back reference, and causes an error only if + there are not that many capturing left parentheses in the entire pat- + tern. In other words, the parentheses that are referenced need not be + to the left of the reference for numbers less than 10. See the section + entitled "Backslash" above for further details of the handling of dig- + its following a backslash. + + A back reference matches whatever actually matched the capturing sub- + pattern in the current subject string, rather than anything matching + the subpattern itself (see "Subpatterns as subroutines" below for a way + of doing that). So the pattern + + (sens|respons)e and \1ibility + + matches "sense and sensibility" and "response and responsibility", but + not "sense and responsibility". If caseful matching is in force at the + time of the back reference, the case of letters is relevant. For exam- + ple, + + ((?i)rah)\s+\1 + + matches "rah rah" and "RAH RAH", but not "RAH rah", even though the + original capturing subpattern is matched caselessly. + + Back references to named subpatterns use the Python syntax (?P=name). + We could rewrite the above example as follows: + + (?<p1>(?i)rah)\s+(?P=p1) + + There may be more than one back reference to the same subpattern. If a + subpattern has not actually been used in a particular match, any back + references to it always fail. For example, the pattern + + (a|(bc))\2 + + always fails if it starts to match "a" rather than "bc". Because there + may be many capturing parentheses in a pattern, all digits following + the backslash are taken as part of a potential back reference number. + If the pattern continues with a digit character, some delimiter must be + used to terminate the back reference. If the PCRE_EXTENDED option is + set, this can be whitespace. Otherwise an empty comment can be used. + + A back reference that occurs inside the parentheses to which it refers + fails when the subpattern is first used, so, for example, (a\1) never + matches. However, such references can be useful inside repeated sub- + patterns. For example, the pattern + + (a|b\1)+ + + matches any number of "a"s and also "aba", "ababbaa" etc. At each iter- + ation of the subpattern, the back reference matches the character + string corresponding to the previous iteration. In order for this to + work, the pattern must be such that the first iteration does not need + to match the back reference. This can be done using alternation, as in + the example above, or by a quantifier with a minimum of zero. + + +ASSERTIONS + + An assertion is a test on the characters following or preceding the + current matching point that does not actually consume any characters. + The simple assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are + described above. More complicated assertions are coded as subpatterns. + There are two kinds: those that look ahead of the current position in + the subject string, and those that look behind it. + + An assertion subpattern is matched in the normal way, except that it + does not cause the current matching position to be changed. Lookahead + assertions start with (?= for positive assertions and (?! for negative + assertions. For example, + + \w+(?=;) + + matches a word followed by a semicolon, but does not include the semi- + colon in the match, and + + foo(?!bar) + + matches any occurrence of "foo" that is not followed by "bar". Note + that the apparently similar pattern + + (?!foo)bar + + does not find an occurrence of "bar" that is preceded by something + other than "foo"; it finds any occurrence of "bar" whatsoever, because + the assertion (?!foo) is always true when the next three characters are + "bar". A lookbehind assertion is needed to achieve this effect. + + If you want to force a matching failure at some point in a pattern, the + most convenient way to do it is with (?!) because an empty string + always matches, so an assertion that requires there not to be an empty + string must always fail. + + Lookbehind assertions start with (?<= for positive assertions and (?<! + for negative assertions. For example, + + (?<!foo)bar + + does find an occurrence of "bar" that is not preceded by "foo". The + contents of a lookbehind assertion are restricted such that all the + strings it matches must have a fixed length. However, if there are sev- + eral alternatives, they do not all have to have the same fixed length. + Thus + + (?<=bullock|donkey) + + is permitted, but + + (?<!dogs?|cats?) + + causes an error at compile time. Branches that match different length + strings are permitted only at the top level of a lookbehind assertion. + This is an extension compared with Perl (at least for 5.8), which + requires all branches to match the same length of string. An assertion + such as + + (?<=ab(c|de)) + + is not permitted, because its single top-level branch can match two + different lengths, but it is acceptable if rewritten to use two top- + level branches: + + (?<=abc|abde) + + The implementation of lookbehind assertions is, for each alternative, + to temporarily move the current position back by the fixed width and + then try to match. If there are insufficient characters before the cur- + rent position, the match is deemed to fail. + + PCRE does not allow the \C escape (which matches a single byte in UTF-8 + mode) to appear in lookbehind assertions, because it makes it impossi- + ble to calculate the length of the lookbehind. + + Atomic groups can be used in conjunction with lookbehind assertions to + specify efficient matching at the end of the subject string. Consider a + simple pattern such as + + abcd$ + + when applied to a long string that does not match. Because matching + proceeds from left to right, PCRE will look for each "a" in the subject + and then see if what follows matches the rest of the pattern. If the + pattern is specified as + + ^.*abcd$ + + the initial .* matches the entire string at first, but when this fails + (because there is no following "a"), it backtracks to match all but the + last character, then all but the last two characters, and so on. Once + again the search for "a" covers the entire string, from right to left, + so we are no better off. However, if the pattern is written as + + ^(?>.*)(?<=abcd) + + or, equivalently, + + ^.*+(?<=abcd) + + there can be no backtracking for the .* item; it can match only the + entire string. The subsequent lookbehind assertion does a single test + on the last four characters. If it fails, the match fails immediately. + For long strings, this approach makes a significant difference to the + processing time. + + Several assertions (of any sort) may occur in succession. For example, + + (?<=\d{3})(?<!999)foo + + matches "foo" preceded by three digits that are not "999". Notice that + each of the assertions is applied independently at the same point in + the subject string. First there is a check that the previous three + characters are all digits, and then there is a check that the same + three characters are not "999". This pattern does not match "foo" pre- + ceded by six characters, the first of which are digits and the last + three of which are not "999". For example, it doesn't match "123abc- + foo". A pattern to do that is + + (?<=\d{3}...)(?<!999)foo + + This time the first assertion looks at the preceding six characters, + checking that the first three are digits, and then the second assertion + checks that the preceding three characters are not "999". + + Assertions can be nested in any combination. For example, + + (?<=(?<!foo)bar)baz + + matches an occurrence of "baz" that is preceded by "bar" which in turn + is not preceded by "foo", while + + (?<=\d{3}(?!999)...)foo + + is another pattern which matches "foo" preceded by three digits and any + three characters that are not "999". + + Assertion subpatterns are not capturing subpatterns, and may not be + repeated, because it makes no sense to assert the same thing several + times. If any kind of assertion contains capturing subpatterns within + it, these are counted for the purposes of numbering the capturing sub- + patterns in the whole pattern. However, substring capturing is carried + out only for positive assertions, because it does not make sense for + negative assertions. + + +CONDITIONAL SUBPATTERNS + + It is possible to cause the matching process to obey a subpattern con- + ditionally or to choose between two alternative subpatterns, depending + on the result of an assertion, or whether a previous capturing + subpattern matched or not. The two possible forms of conditional sub- + pattern are + + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) + + If the condition is satisfied, the yes-pattern is used; otherwise the + no-pattern (if present) is used. If there are more than two alterna- + tives in the subpattern, a compile-time error occurs. + + There are three kinds of condition. If the text between the parentheses + consists of a sequence of digits, the condition is satisfied if the + capturing subpattern of that number has previously matched. The number + must be greater than zero. Consider the following pattern, which con- + tains non-significant white space to make it more readable (assume the + PCRE_EXTENDED option) and to divide it into three parts for ease of + discussion: + + ( \( )? [^()]+ (?(1) \) ) + + The first part matches an optional opening parenthesis, and if that + character is present, sets it as the first captured substring. The sec- + ond part matches one or more characters that are not parentheses. The + third part is a conditional subpattern that tests whether the first set + of parentheses matched or not. If they did, that is, if subject started + with an opening parenthesis, the condition is true, and so the yes-pat- + tern is executed and a closing parenthesis is required. Otherwise, + since no-pattern is not present, the subpattern matches nothing. In + other words, this pattern matches a sequence of non-parentheses, + optionally enclosed in parentheses. + + If the condition is the string (R), it is satisfied if a recursive call + to the pattern or subpattern has been made. At "top level", the condi- + tion is false. This is a PCRE extension. Recursive patterns are + described in the next section. + + If the condition is not a sequence of digits or (R), it must be an + assertion. This may be a positive or negative lookahead or lookbehind + assertion. Consider this pattern, again containing non-significant + white space, and with the two alternatives on the second line: + + (?(?=[^a-z]*[a-z]) + \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) + + The condition is a positive lookahead assertion that matches an + optional sequence of non-letters followed by a letter. In other words, + it tests for the presence of at least one letter in the subject. If a + letter is found, the subject is matched against the first alternative; + otherwise it is matched against the second. This pattern matches + strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are + letters and dd are digits. + + +COMMENTS + + The sequence (?# marks the start of a comment which continues up to the + next closing parenthesis. Nested parentheses are not permitted. The + characters that make up a comment play no part in the pattern matching + at all. + + If the PCRE_EXTENDED option is set, an unescaped # character outside a + character class introduces a comment that continues up to the next new- + line character in the pattern. + + +RECURSIVE PATTERNS + + Consider the problem of matching a string in parentheses, allowing for + unlimited nested parentheses. Without the use of recursion, the best + that can be done is to use a pattern that matches up to some fixed + depth of nesting. It is not possible to handle an arbitrary nesting + depth. Perl has provided an experimental facility that allows regular + expressions to recurse (amongst other things). It does this by interpo- + lating Perl code in the expression at run time, and the code can refer + to the expression itself. A Perl pattern to solve the parentheses prob- + lem can be created like this: + + $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; + + The (?p{...}) item interpolates Perl code at run time, and in this case + refers recursively to the pattern in which it appears. Obviously, PCRE + cannot support the interpolation of Perl code. Instead, it supports + some special syntax for recursion of the entire pattern, and also for + individual subpattern recursion. + + The special item that consists of (? followed by a number greater than + zero and a closing parenthesis is a recursive call of the subpattern of + the given number, provided that it occurs inside that subpattern. (If + not, it is a "subroutine" call, which is described in the next sec- + tion.) The special item (?R) is a recursive call of the entire regular + expression. + + For example, this PCRE pattern solves the nested parentheses problem + (assume the PCRE_EXTENDED option is set so that white space is + ignored): + + \( ( (?>[^()]+) | (?R) )* \) + + First it matches an opening parenthesis. Then it matches any number of + substrings which can either be a sequence of non-parentheses, or a + recursive match of the pattern itself (that is a correctly parenthe- + sized substring). Finally there is a closing parenthesis. + + If this were part of a larger pattern, you would not want to recurse + the entire pattern, so instead you could use this: + + ( \( ( (?>[^()]+) | (?1) )* \) ) + + We have put the pattern into parentheses, and caused the recursion to + refer to them instead of the whole pattern. In a larger pattern, keep- + ing track of parenthesis numbers can be tricky. It may be more conve- + nient to use named parentheses instead. For this, PCRE uses (?P>name), + which is an extension to the Python syntax that PCRE uses for named + parentheses (Perl does not provide named parentheses). We could rewrite + the above example as follows: + + (?P<pn> \( ( (?>[^()]+) | (?P>pn) )* \) ) + + This particular example pattern contains nested unlimited repeats, and + so the use of atomic grouping for matching strings of non-parentheses + is important when applying the pattern to strings that do not match. + For example, when this pattern is applied to + + (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() + + it yields "no match" quickly. However, if atomic grouping is not used, + the match runs for a very long time indeed because there are so many + different ways the + and * repeats can carve up the subject, and all + have to be tested before failure can be reported. + + At the end of a match, the values set for any capturing subpatterns are + those from the outermost level of the recursion at which the subpattern + value is set. If you want to obtain intermediate values, a callout + function can be used (see below and the pcrecallout documentation). If + the pattern above is matched against + + (ab(cd)ef) + + the value for the capturing parentheses is "ef", which is the last + value taken on at the top level. If additional parentheses are added, + giving + + \( ( ( (?>[^()]+) | (?R) )* ) \) + ^ ^ + ^ ^ + + the string they capture is "ab(cd)ef", the contents of the top level + parentheses. If there are more than 15 capturing parentheses in a pat- + tern, PCRE has to obtain extra memory to store data during a recursion, + which it does by using pcre_malloc, freeing it via pcre_free after- + wards. If no memory can be obtained, the match fails with the + PCRE_ERROR_NOMEMORY error. + + Do not confuse the (?R) item with the condition (R), which tests for + recursion. Consider this pattern, which matches text in angle brack- + ets, allowing for arbitrary nesting. Only digits are allowed in nested + brackets (that is, when recursing), whereas any characters are permit- + ted at the outer level. + + < (?: (?(R) \d++ | [^<>]*+) | (?R)) * > + + In this pattern, (?(R) is the start of a conditional subpattern, with + two different alternatives for the recursive and non-recursive cases. + The (?R) item is the actual recursive call. + + +SUBPATTERNS AS SUBROUTINES + + If the syntax for a recursive subpattern reference (either by number or + by name) is used outside the parentheses to which it refers, it oper- + ates like a subroutine in a programming language. An earlier example + pointed out that the pattern + + (sens|respons)e and \1ibility + + matches "sense and sensibility" and "response and responsibility", but + not "sense and responsibility". If instead the pattern + + (sens|respons)e and (?1)ibility + + is used, it does match "sense and responsibility" as well as the other + two strings. Such references must, however, follow the subpattern to + which they refer. + + +CALLOUTS + + Perl has a feature whereby using the sequence (?{...}) causes arbitrary + Perl code to be obeyed in the middle of matching a regular expression. + This makes it possible, amongst other things, to extract different sub- + strings that match the same pair of parentheses when there is a repeti- + tion. + + PCRE provides a similar feature, but of course it cannot obey arbitrary + Perl code. The feature is called "callout". The caller of PCRE provides + an external function by putting its entry point in the global variable + pcre_callout. By default, this variable contains NULL, which disables + all calling out. + + Within a regular expression, (?C) indicates the points at which the + external function is to be called. If you want to identify different + callout points, you can put a number less than 256 after the letter C. + The default value is zero. For example, this pattern has two callout + points: + + (?C1)abc(?C2)def + + During matching, when PCRE reaches a callout point (and pcre_callout is + set), the external function is called. It is provided with the number + of the callout, and, optionally, one item of data originally supplied + by the caller of pcre_exec(). The callout function may cause matching + to backtrack, or to fail altogether. A complete description of the + interface to the callout function is given in the pcrecallout documen- + tation. + +Last updated: 03 February 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE PERFORMANCE + + Certain items that may appear in regular expression patterns are more + efficient than others. It is more efficient to use a character class + like [aeiou] than a set of alternatives such as (a|e|i|o|u). In gen- + eral, the simplest construction that provides the required behaviour is + usually the most efficient. Jeffrey Friedl's book contains a lot of + discussion about optimizing regular expressions for efficient perfor- + mance. + + When a pattern begins with .* not in parentheses, or in parentheses + that are not the subject of a backreference, and the PCRE_DOTALL option + is set, the pattern is implicitly anchored by PCRE, since it can match + only at the start of a subject string. However, if PCRE_DOTALL is not + set, PCRE cannot make this optimization, because the . metacharacter + does not then match a newline, and if the subject string contains new- + lines, the pattern may match from the character immediately following + one of them instead of from the very start. For example, the pattern + + .*second + + matches the subject "first\nand second" (where \n stands for a newline + character), with the match starting at the seventh character. In order + to do this, PCRE has to retry the match starting after every newline in + the subject. + + If you are using such a pattern with subject strings that do not con- + tain newlines, the best performance is obtained by setting PCRE_DOTALL, + or starting the pattern with ^.* to indicate explicit anchoring. That + saves PCRE from having to scan along the subject looking for a newline + to restart at. + + Beware of patterns that contain nested indefinite repeats. These can + take a long time to run when applied to a string that does not match. + Consider the pattern fragment + + (a+)* + + This can match "aaaa" in 33 different ways, and this number increases + very rapidly as the string gets longer. (The * repeat can match 0, 1, + 2, 3, or 4 times, and for each of those cases other than 0, the + + repeats can match different numbers of times.) When the remainder of + the pattern is such that the entire match is going to fail, PCRE has in + principle to try every possible variation, and this can take an + extremely long time. + + An optimization catches some of the more simple cases such as + + (a+)*b + + where a literal character follows. Before embarking on the standard + matching procedure, PCRE checks that there is a "b" later in the sub- + ject string, and if there is not, it fails the match immediately. How- + ever, when there is no following literal this optimization cannot be + used. You can see the difference by comparing the behaviour of + + (a+)*\d + + with the pattern above. The former gives a failure almost instantly + when applied to a whole line of "a" characters, whereas the latter + takes an appreciable time with strings longer than about 20 characters. + +Last updated: 03 February 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions. + +SYNOPSIS OF POSIX API + #include <pcreposix.h> + + int regcomp(regex_t *preg, const char *pattern, + int cflags); + + int regexec(regex_t *preg, const char *string, + size_t nmatch, regmatch_t pmatch[], int eflags); + + size_t regerror(int errcode, const regex_t *preg, + char *errbuf, size_t errbuf_size); + + void regfree(regex_t *preg); + + +DESCRIPTION + + This set of functions provides a POSIX-style API to the PCRE regular + expression package. See the pcreapi documentation for a description of + the native API, which contains additional functionality. + + The functions described here are just wrapper functions that ultimately + call the PCRE native API. Their prototypes are defined in the + pcreposix.h header file, and on Unix systems the library itself is + called pcreposix.a, so can be accessed by adding -lpcreposix to the + command for linking an application which uses them. Because the POSIX + functions call the native ones, it is also necessary to add -lpcre. + + I have implemented only those option bits that can be reasonably mapped + to PCRE native options. In addition, the options REG_EXTENDED and + REG_NOSUB are defined with the value zero. They have no effect, but + since programs that are written to the POSIX interface often use them, + this makes it easier to slot in PCRE as a replacement library. Other + POSIX options are not even defined. + + When PCRE is called via these functions, it is only the API that is + POSIX-like in style. The syntax and semantics of the regular expres- + sions themselves are still those of Perl, subject to the setting of + various PCRE options, as described below. "POSIX-like in style" means + that the API approximates to the POSIX definition; it is not fully + POSIX-compatible, and in multi-byte encoding domains it is probably + even less compatible. + + The header for these functions is supplied as pcreposix.h to avoid any + potential clash with other POSIX libraries. It can, of course, be + renamed or aliased as regex.h, which is the "correct" name. It provides + two structure types, regex_t for compiled internal forms, and reg- + match_t for returning captured substrings. It also defines some con- + stants whose names start with "REG_"; these are used for setting + options and identifying error codes. + + +COMPILING A PATTERN + + The function regcomp() is called to compile a pattern into an internal + form. The pattern is a C string terminated by a binary zero, and is + passed in the argument pattern. The preg argument is a pointer to a + regex_t structure which is used as a base for storing information about + the compiled expression. + + The argument cflags is either zero, or contains one or more of the bits + defined by the following macros: + + REG_ICASE + + The PCRE_CASELESS option is set when the expression is passed for com- + pilation to the native function. + + REG_NEWLINE + + The PCRE_MULTILINE option is set when the expression is passed for com- + pilation to the native function. Note that this does not mimic the + defined POSIX behaviour for REG_NEWLINE (see the following section). + + In the absence of these flags, no options are passed to the native + function. This means the the regex is compiled with PCRE default + semantics. In particular, the way it handles newline characters in the + subject string is the Perl way, not the POSIX way. Note that setting + PCRE_MULTILINE has only some of the effects specified for REG_NEWLINE. + It does not affect the way newlines are matched by . (they aren't) or + by a negative class such as [^a] (they are). + + The yield of regcomp() is zero on success, and non-zero otherwise. The + preg structure is filled in on success, and one member of the structure + is public: re_nsub contains the number of capturing subpatterns in the + regular expression. Various error codes are defined in the header file. + + +MATCHING NEWLINE CHARACTERS + + This area is not simple, because POSIX and Perl take different views of + things. It is not possible to get PCRE to obey POSIX semantics, but + then PCRE was never intended to be a POSIX engine. The following table + lists the different possibilities for matching newline characters in + PCRE: + + Default Change with + + . matches newline no PCRE_DOTALL + newline matches [^a] yes not changeable + $ matches \n at end yes PCRE_DOLLARENDONLY + $ matches \n in middle no PCRE_MULTILINE + ^ matches \n in middle no PCRE_MULTILINE + + This is the equivalent table for POSIX: + + Default Change with + + . matches newline yes REG_NEWLINE + newline matches [^a] yes REG_NEWLINE + $ matches \n at end no REG_NEWLINE + $ matches \n in middle no REG_NEWLINE + ^ matches \n in middle no REG_NEWLINE + + PCRE's behaviour is the same as Perl's, except that there is no equiva- + lent for PCRE_DOLLARENDONLY in Perl. In both PCRE and Perl, there is no + way to stop newline from matching [^a]. + + The default POSIX newline handling can be obtained by setting + PCRE_DOTALL and PCRE_DOLLARENDONLY, but there is no way to make PCRE + behave exactly as for the REG_NEWLINE action. + + +MATCHING A PATTERN + + The function regexec() is called to match a pre-compiled pattern preg + against a given string, which is terminated by a zero byte, subject to + the options in eflags. These can be: + + REG_NOTBOL + + The PCRE_NOTBOL option is set when calling the underlying PCRE matching + function. + + REG_NOTEOL + + The PCRE_NOTEOL option is set when calling the underlying PCRE matching + function. + + The portion of the string that was matched, and also any captured sub- + strings, are returned via the pmatch argument, which points to an array + of nmatch structures of type regmatch_t, containing the members rm_so + and rm_eo. These contain the offset to the first character of each sub- + string and the offset to the first character after the end of each sub- + string, respectively. The 0th element of the vector relates to the + entire portion of string that was matched; subsequent elements relate + to the capturing subpatterns of the regular expression. Unused entries + in the array have both structure members set to -1. + + A successful match yields a zero return; various error codes are + defined in the header file, of which REG_NOMATCH is the "expected" + failure code. + + +ERROR MESSAGES + + The regerror() function maps a non-zero errorcode from either regcomp() + or regexec() to a printable message. If preg is not NULL, the error + should have arisen from the use of that structure. A message terminated + by a binary zero is placed in errbuf. The length of the message, + including the zero, is limited to errbuf_size. The yield of the func- + tion is the size of buffer needed to hold the whole message. + + +STORAGE + + Compiling a regular expression causes memory to be allocated and asso- + ciated with the preg structure. The function regfree() frees all such + memory, after which preg may no longer be used as a compiled expres- + sion. + + +AUTHOR + + Philip Hazel <ph10@cam.ac.uk> + University Computing Service, + Cambridge CB2 3QG, England. + +Last updated: 03 February 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + +PCRE(3) PCRE(3) + + + +NAME + PCRE - Perl-compatible regular expressions + +PCRE SAMPLE PROGRAM + + A simple, complete demonstration program, to get you started with using + PCRE, is supplied in the file pcredemo.c in the PCRE distribution. + + The program compiles the regular expression that is its first argument, + and matches it against the subject string in its second argument. No + PCRE options are set, and default character tables are used. If match- + ing succeeds, the program outputs the portion of the subject that + matched, together with the contents of any captured substrings. + + If the -g option is given on the command line, the program then goes on + to check for further matches of the same regular expression in the same + subject string. The logic is a little bit tricky because of the possi- + bility of matching an empty string. Comments in the code explain what + is going on. + + On a Unix system that has PCRE installed in /usr/local, you can compile + the demonstration program using a command like this: + + gcc -o pcredemo pcredemo.c -I/usr/local/include \ + -L/usr/local/lib -lpcre + + Then you can run simple tests like this: + + ./pcredemo 'cat|dog' 'the cat sat on the mat' + ./pcredemo -g 'cat|dog' 'the dog sat on the cat' + + Note that there is a much more comprehensive test program, called + pcretest, which supports many more facilities for testing regular + expressions and the PCRE library. The pcredemo program is provided as a + simple coding example. + + On some operating systems (e.g. Solaris) you may get an error like this + when you try to run pcredemo: + + ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or + directory + + This is caused by the way shared library support works on those sys- + tems. You need to add + + -R/usr/local/lib + + to the compile command to get round this problem. + +Last updated: 28 January 2003 +Copyright (c) 1997-2003 University of Cambridge. +----------------------------------------------------------------------------- + diff --git a/external-libs/pcre/doc/pcre_compile.3 b/external-libs/pcre/doc/pcre_compile.3 new file mode 100644 index 00000000..a8273151 --- /dev/null +++ b/external-libs/pcre/doc/pcre_compile.3 @@ -0,0 +1,59 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR, +.ti +5n +.B const char **\fIerrptr\fR, int *\fIerroffset\fR, +.ti +5n +.B const unsigned char *\fItableptr\fR); + +.SH DESCRIPTION +.rs +.sp +This function compiles a regular expression into an internal form. Its +arguments are: + + \fIpattern\fR A zero-terminated string containing the + regular expression to be compiled + \fIoptions\fR Zero or more option bits + \fIerrptr\fR Where to put an error message + \fIerroffset\fR Offset in pattern where error was found + \fItableptr\fR Pointer to character tables, or NULL to + use the built-in default + +The option bits are: + + PCRE_ANCHORED Force pattern anchoring + PCRE_CASELESS Do caseless matching + PCRE_DOLLAR_ENDONLY $ not to match newline at end + PCRE_DOTALL . matches anything including NL + PCRE_EXTENDED Ignore whitespace and # comments + PCRE_EXTRA PCRE extra features + (not much use currently) + PCRE_MULTILINE ^ and $ match newlines within data + PCRE_NO_AUTO_CAPTURE Disable numbered capturing paren- + theses (named ones available) + PCRE_UNGREEDY Invert greediness of quantifiers + PCRE_UTF8 Run in UTF-8 mode + PCRE_NO_UTF8_CHECK Do not check the pattern for UTF-8 + validity (only relevant if + PCRE_UTF8 is set) + +PCRE must be compiled with UTF-8 support in order to use PCRE_UTF8 +(or PCRE_NO_UTF8_CHECK). + +The yield of the function is a pointer to a private data structure that +contains the compiled pattern, or NULL if an error was detected. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_config.3 b/external-libs/pcre/doc/pcre_config.3 new file mode 100644 index 00000000..3a0e6998 --- /dev/null +++ b/external-libs/pcre/doc/pcre_config.3 @@ -0,0 +1,45 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR); + +.SH DESCRIPTION +.rs +.sp +This function makes it possible for a client program to find out which optional +features are available in the version of the PCRE library it is using. Its +arguments are as follows: + + \fIwhat\fR A code specifying what information is required + \fIwhere\fR Points to where to put the data + +The available codes are: + + PCRE_CONFIG_LINK_SIZE Internal link size: 2, 3, or 4 + PCRE_CONFIG_MATCH_LIMIT Internal resource limit + PCRE_CONFIG_NEWLINE Value of the newline character + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + Threshold of return slots, above + which \fBmalloc()\fR is used by + the POSIX API + PCRE_CONFIG_STACKRECURSE Recursion implementation (1=stack 0=heap) + PCRE_CONFIG_UTF8 Availability of UTF-8 support (1=yes 0=no) + +The function yields 0 on success or PCRE_ERROR_BADOPTION otherwise. + +There is a complete description of the PCRE native API in the +.\" HREF +\fBpcreapi\fR +.\" +page, and a description of the POSIX API in the +.\" HREF +\fBpcreposix\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_copy_named_substring.3 b/external-libs/pcre/doc/pcre_copy_named_substring.3 new file mode 100644 index 00000000..915bd0a5 --- /dev/null +++ b/external-libs/pcre/doc/pcre_copy_named_substring.3 @@ -0,0 +1,40 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_copy_named_substring(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, const char *\fIstringname\fR, +.ti +5n +.B char *\fIbuffer\fR, int \fIbuffersize\fR); + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring, identified +by name, into a given buffer. The arguments are: + + \fIcode\fR Pattern that was successfully matched + \fIsubject\fR Subject that has been successfully matched + \fIovector\fR Offset vector that \fBpcre_exec()\fR used + \fIstringcount\fR Value returned by \fBpcre_exec()\fR + \fIstringname\fR Name of the required substring + \fIbuffer\fR Buffer to receive the string + \fIbuffersize\fR Size of buffer + +The yield is the length of the substring, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string name is invalid. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_copy_substring.3 b/external-libs/pcre/doc/pcre_copy_substring.3 new file mode 100644 index 00000000..d61b99bf --- /dev/null +++ b/external-libs/pcre/doc/pcre_copy_substring.3 @@ -0,0 +1,37 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR, +.ti +5n +.B int \fIbuffersize\fR); + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring into a given +buffer. The arguments are: + + \fIsubject\fR Subject that has been successfully matched + \fIovector\fR Offset vector that \fBpcre_exec()\fR used + \fIstringcount\fR Value returned by \fBpcre_exec()\fR + \fIstringnumber\fR Number of the required substring + \fIbuffer\fR Buffer to receive the string + \fIbuffersize\fR Size of buffer + +The yield is the legnth of the string, PCRE_ERROR_NOMEMORY if the buffer was +too small, or PCRE_ERROR_NOSUBSTRING if the string number is invalid. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_exec.3 b/external-libs/pcre/doc/pcre_exec.3 new file mode 100644 index 00000000..0d6c3805 --- /dev/null +++ b/external-libs/pcre/doc/pcre_exec.3 @@ -0,0 +1,48 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," +.ti +5n +.B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR, +.ti +5n +.B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR); + +.SH DESCRIPTION +.rs +.sp +This function matches a compiled regular expression against a given subject +string, and returns offsets to capturing subexpressions. Its arguments are: + + \fIcode\fR Points to the compiled pattern + \fIextra\fR Points to an associated \fBpcre_extra\fR structure, + or is NULL + \fIsubject\fR Points to the subject string + \fIlength\fR Length of the subject string, in bytes + \fIstartoffset\fR Offset in bytes in the subject at which to + start matching + \fIoptions\fR Option bits + \fIovector\fR Points to a vector of ints for result offsets + \fIovecsize\fR Size of the vector (a multiple of 3) + +The options are: + + PCRE_ANCHORED Match only at the first position + PCRE_NOTBOL Subject is not the beginning of a line + PCRE_NOTEOL Subject is not the end of a line + PCRE_NOTEMPTY An empty string is not a valid match + PCRE_NO_UTF8_CHECK Do not check the subject for UTF-8 + validity (only relevant if PCRE_UTF8 + was set at compile time) + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_free_substring.3 b/external-libs/pcre/doc/pcre_free_substring.3 new file mode 100644 index 00000000..3fcaf117 --- /dev/null +++ b/external-libs/pcre/doc/pcre_free_substring.3 @@ -0,0 +1,24 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B void pcre_free_substring(const char *\fIstringptr\fR); + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for freeing the store obtained by a previous +call to \fBpcre_get_substring()\fR or \fBpcre_get_named_substring()\fR. Its +only argument is a pointer to the string. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_free_substring_list.3 b/external-libs/pcre/doc/pcre_free_substring_list.3 new file mode 100644 index 00000000..73d5993d --- /dev/null +++ b/external-libs/pcre/doc/pcre_free_substring_list.3 @@ -0,0 +1,24 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B void pcre_free_substring_list(const char **\fIstringptr\fR); + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for freeing the store obtained by a previous +call to \fBpcre_get_substring_list()\fR. Its only argument is a pointer to the +list of string pointers. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_fullinfo.3 b/external-libs/pcre/doc/pcre_fullinfo.3 new file mode 100644 index 00000000..06de985f --- /dev/null +++ b/external-libs/pcre/doc/pcre_fullinfo.3 @@ -0,0 +1,53 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," +.ti +5n +.B int \fIwhat\fR, void *\fIwhere\fR); + +.SH DESCRIPTION +.rs +.sp +This function returns information about a compiled pattern. Its arguments are: + + \fIcode\fR Compiled regular expression + \fIextra\fR Result of \fBpcre_study()\fR or NULL + \fIwhat\fR What information is required + \fIwhere\fR Where to put the information + +The following information is available: + + PCRE_INFO_BACKREFMAX Number of highest back reference + PCRE_INFO_CAPTURECOUNT Number of capturing subpatterns + PCRE_INFO_FIRSTBYTE Fixed first byte for a match, or + -1 for start of string + or after newline, or + -2 otherwise + PCRE_INFO_FIRSTTABLE Table of first bytes + (after studying) + PCRE_INFO_LASTLITERAL Literal last byte required + PCRE_INFO_NAMECOUNT Number of named subpatterns + PCRE_INFO_NAMEENTRYSIZE Size of name table entry + PCRE_INFO_NAMETABLE Pointer to name table + PCRE_INFO_OPTIONS Options used for compilation + PCRE_INFO_SIZE Size of compiled pattern + +The yield of the function is zero on success or: + + PCRE_ERROR_NULL the argument \fIcode\fR was NULL + the argument \fIwhere\fR was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of \fIwhat\fR was invalid + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_get_named_substring.3 b/external-libs/pcre/doc/pcre_get_named_substring.3 new file mode 100644 index 00000000..6d3f80ea --- /dev/null +++ b/external-libs/pcre/doc/pcre_get_named_substring.3 @@ -0,0 +1,40 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_get_named_substring(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, const char *\fIstringname\fR, +.ti +5n +.B const char **\fIstringptr\fR); + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring by name. The +arguments are: + + \fIcode\fR Compiled pattern + \fIsubject\fR Subject that has been successfully matched + \fIovector\fR Offset vector that \fBpcre_exec()\fR used + \fIstringcount\fR Value returned by \fBpcre_exec()\fR + \fIstringname\fR Name of the required substring + \fIstringptr\fR Where to put the string pointer + +The yield is the length of the extracted substring, PCRE_ERROR_NOMEMORY if +sufficient memory could not be obtained, or PCRE_ERROR_NOSUBSTRING if the +string name is invalid. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_get_stringnumber.3 b/external-libs/pcre/doc/pcre_get_stringnumber.3 new file mode 100644 index 00000000..f6c9357f --- /dev/null +++ b/external-libs/pcre/doc/pcre_get_stringnumber.3 @@ -0,0 +1,31 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_get_stringnumber(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIname\fR); + +.SH DESCRIPTION +.rs +.sp +This convenience function finds the number of a named substring capturing +parenthesis in a compiled pattern. Its arguments are: + + \fIcode\fR Compiled regular expression + \fIname\fR Name whose number is required + +The yield of the function is the number of the parenthesis if the name is +found, or PCRE_ERROR_NOSUBSTRING otherwise. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_get_substring.3 b/external-libs/pcre/doc/pcre_get_substring.3 new file mode 100644 index 00000000..4c92c9c5 --- /dev/null +++ b/external-libs/pcre/doc/pcre_get_substring.3 @@ -0,0 +1,37 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, int \fIstringnumber\fR, +.ti +5n +.B const char **\fIstringptr\fR); + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a captured substring. The +arguments are: + + \fIsubject\fR Subject that has been successfully matched + \fIovector\fR Offset vector that \fBpcre_exec()\fR used + \fIstringcount\fR Value returned by \fBpcre_exec()\fR + \fIstringnumber\fR Number of the required substring + \fIstringptr\fR Where to put the string pointer + +The yield is the length of the substring, PCRE_ERROR_NOMEMORY if sufficient +memory could not be obtained, or PCRE_ERROR_NOSUBSTRING if the string number is +invalid. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_get_substring_list.3 b/external-libs/pcre/doc/pcre_get_substring_list.3 new file mode 100644 index 00000000..69090e1b --- /dev/null +++ b/external-libs/pcre/doc/pcre_get_substring_list.3 @@ -0,0 +1,33 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_get_substring_list(const char *\fIsubject\fR, +.ti +5n +.B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);" + +.SH DESCRIPTION +.rs +.sp +This is a convenience function for extracting a list of all the captured +substrings. The arguments are: + + \fIsubject\fR Subject that has been successfully matched + \fIovector\fR Offset vector that \fBpcre_exec\fR used + \fIstringcount\fR Value returned by \fBpcre_exec\fR + \fIlistptr\fR Where to put a pointer to the list + +The yield is zero on success or PCRE_ERROR_NOMEMORY if sufficient memory could +not be obtained. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_info.3 b/external-libs/pcre/doc/pcre_info.3 new file mode 100644 index 00000000..c4970764 --- /dev/null +++ b/external-libs/pcre/doc/pcre_info.3 @@ -0,0 +1,23 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int +.B *\fIfirstcharptr\fR); + +.SH DESCRIPTION +.rs +.sp +This function is obsolete. You should be using \fBpcre_fullinfo()\fR instead. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_maketables.3 b/external-libs/pcre/doc/pcre_maketables.3 new file mode 100644 index 00000000..7d459ed4 --- /dev/null +++ b/external-libs/pcre/doc/pcre_maketables.3 @@ -0,0 +1,26 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B const unsigned char *pcre_maketables(void); + +.SH DESCRIPTION +.rs +.sp +This function builds a set of character tables which can be passed to +\fBpcre_compile()\fR to override PCRE's internal, built-in tables (which were +made by \fBpcre_maketables()\fR when PCRE was compiled). You might want to do +this if you are using a non-standard locale. The function yields a pointer to +the tables. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_study.3 b/external-libs/pcre/doc/pcre_study.3 new file mode 100644 index 00000000..69ff20e4 --- /dev/null +++ b/external-libs/pcre/doc/pcre_study.3 @@ -0,0 +1,36 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR, +.ti +5n +.B const char **\fIerrptr\fR); + +.SH DESCRIPTION +.rs +.sp +This function studies a compiled pattern, to see if additional information can +be extracted that might speed up matching. Its arguments are: + + \fIcode\fR A compiled regular expression + \fIoptions\fR Options for \fBpcre_study()\fR + \fIerrptr\fR Where to put an error message + +If the function returns NULL, either it could not find any additional +information, or there was an error. You can tell the difference by looking at +the error value. It is NULL in first case. + +There are currently no options defined; the value of the second argument should +always be zero. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcre_version.3 b/external-libs/pcre/doc/pcre_version.3 new file mode 100644 index 00000000..6f981224 --- /dev/null +++ b/external-libs/pcre/doc/pcre_version.3 @@ -0,0 +1,23 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B char *pcre_version(void); + +.SH DESCRIPTION +.rs +.sp +This function returns a character string that gives the version number of the +PCRE library, and its date of release. + +There is a complete description of the PCRE API in the +.\" HREF +\fBpcreapi\fR +.\" +page. diff --git a/external-libs/pcre/doc/pcreapi.3 b/external-libs/pcre/doc/pcreapi.3 new file mode 100644 index 00000000..4c7d43c3 --- /dev/null +++ b/external-libs/pcre/doc/pcreapi.3 @@ -0,0 +1,1082 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH SYNOPSIS OF PCRE API +.rs +.sp +.B #include <pcre.h> +.PP +.SM +.br +.B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR, +.ti +5n +.B const char **\fIerrptr\fR, int *\fIerroffset\fR, +.ti +5n +.B const unsigned char *\fItableptr\fR); +.PP +.br +.B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR, +.ti +5n +.B const char **\fIerrptr\fR); +.PP +.br +.B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," +.ti +5n +.B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR, +.ti +5n +.B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR); +.PP +.br +.B int pcre_copy_named_substring(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, const char *\fIstringname\fR, +.ti +5n +.B char *\fIbuffer\fR, int \fIbuffersize\fR); +.PP +.br +.B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR, +.ti +5n +.B int \fIbuffersize\fR); +.PP +.br +.B int pcre_get_named_substring(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, const char *\fIstringname\fR, +.ti +5n +.B const char **\fIstringptr\fR); +.PP +.br +.B int pcre_get_stringnumber(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIname\fR); +.PP +.br +.B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, int \fIstringnumber\fR, +.ti +5n +.B const char **\fIstringptr\fR); +.PP +.br +.B int pcre_get_substring_list(const char *\fIsubject\fR, +.ti +5n +.B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);" +.PP +.br +.B void pcre_free_substring(const char *\fIstringptr\fR); +.PP +.br +.B void pcre_free_substring_list(const char **\fIstringptr\fR); +.PP +.br +.B const unsigned char *pcre_maketables(void); +.PP +.br +.B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," +.ti +5n +.B int \fIwhat\fR, void *\fIwhere\fR); +.PP +.br +.B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int +.B *\fIfirstcharptr\fR); +.PP +.br +.B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR); +.PP +.br +.B char *pcre_version(void); +.PP +.br +.B void *(*pcre_malloc)(size_t); +.PP +.br +.B void (*pcre_free)(void *); +.PP +.br +.B void *(*pcre_stack_malloc)(size_t); +.PP +.br +.B void (*pcre_stack_free)(void *); +.PP +.br +.B int (*pcre_callout)(pcre_callout_block *); + +.SH PCRE API +.rs +.sp +PCRE has its own native API, which is described in this document. There is also +a set of wrapper functions that correspond to the POSIX regular expression API. +These are described in the \fBpcreposix\fR documentation. + +The native API function prototypes are defined in the header file \fBpcre.h\fR, +and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be +accessed by adding \fB-lpcre\fR to the command for linking an application which +calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to +contain the major and minor release numbers for the library. Applications can +use these to include support for different releases. + +The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR +are used for compiling and matching regular expressions. A sample program that +demonstrates the simplest way of using them is given in the file +\fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it. + +There are convenience functions for extracting captured substrings from a +matched subject string. They are: + + \fBpcre_copy_substring()\fR + \fBpcre_copy_named_substring()\fR + \fBpcre_get_substring()\fR + \fBpcre_get_named_substring()\fR + \fBpcre_get_substring_list()\fR + +\fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also +provided, to free the memory used for extracted strings. + +The function \fBpcre_maketables()\fR is used (optionally) to build a set of +character tables in the current locale for passing to \fBpcre_compile()\fR. + +The function \fBpcre_fullinfo()\fR is used to find out information about a +compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only +some of the available information, but is retained for backwards compatibility. +The function \fBpcre_version()\fR returns a pointer to a string containing the +version of PCRE and its date of release. + +The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain +the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions +respectively. PCRE calls the memory management functions via these variables, +so a calling program can replace them if it wishes to intercept the calls. This +should be done before calling any PCRE functions. + +The global variables \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are also +indirections to memory management functions. These special functions are used +only when PCRE is compiled to use the heap for remembering data, instead of +recursive function calls. This is a non-standard way of building PCRE, for use +in environments that have limited stacks. Because of the greater use of memory +management, it runs more slowly. Separate functions are provided so that +special-purpose external code can be used for this case. When used, these +functions are always called in a stack-like manner (last obtained, first +freed), and always for memory blocks of the same size. + +The global variable \fBpcre_callout\fR initially contains NULL. It can be set +by the caller to a "callout" function, which PCRE will then call at specified +points during a matching operation. Details are given in the \fBpcrecallout\fR +documentation. + +.SH MULTITHREADING +.rs +.sp +The PCRE functions can be used in multi-threading applications, with the +proviso that the memory management functions pointed to by \fBpcre_malloc\fR, +\fBpcre_free\fR, \fBpcre_stack_malloc\fR, and \fBpcre_stack_free\fR, and the +callout function pointed to by \fBpcre_callout\fR, are shared by all threads. + +The compiled form of a regular expression is not altered during matching, so +the same compiled pattern can safely be used by several threads at once. + +.SH CHECKING BUILD-TIME OPTIONS +.rs +.sp +.B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR); +.PP +The function \fBpcre_config()\fR makes it possible for a PCRE client to +discover which optional features have been compiled into the PCRE library. The +.\" HREF +\fBpcrebuild\fR +.\" +documentation has more details about these optional features. + +The first argument for \fBpcre_config()\fR is an integer, specifying which +information is required; the second argument is a pointer to a variable into +which the information is placed. The following information is available: + + PCRE_CONFIG_UTF8 + +The output is an integer that is set to one if UTF-8 support is available; +otherwise it is set to zero. + + PCRE_CONFIG_NEWLINE + +The output is an integer that is set to the value of the code that is used for +the newline character. It is either linefeed (10) or carriage return (13), and +should normally be the standard character for your operating system. + + PCRE_CONFIG_LINK_SIZE + +The output is an integer that contains the number of bytes used for internal +linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values +allow larger regular expressions to be compiled, at the expense of slower +matching. The default value of 2 is sufficient for all but the most massive +patterns, since it allows the compiled pattern to be up to 64K in size. + + PCRE_CONFIG_POSIX_MALLOC_THRESHOLD + +The output is an integer that contains the threshold above which the POSIX +interface uses \fBmalloc()\fR for output vectors. Further details are given in +the \fBpcreposix\fR documentation. + + PCRE_CONFIG_MATCH_LIMIT + +The output is an integer that gives the default limit for the number of +internal matching function calls in a \fBpcre_exec()\fR execution. Further +details are given with \fBpcre_exec()\fR below. + + PCRE_CONFIG_STACKRECURSE + +The output is an integer that is set to one if internal recursion is +implemented by recursive function calls that use the stack to remember their +state. This is the usual way that PCRE is compiled. The output is zero if PCRE +was compiled to use blocks of data on the heap instead of recursive function +calls. In this case, \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR are +called to manage memory blocks on the heap, thus avoiding the use of the stack. + +.SH COMPILING A PATTERN +.rs +.sp +.B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR, +.ti +5n +.B const char **\fIerrptr\fR, int *\fIerroffset\fR, +.ti +5n +.B const unsigned char *\fItableptr\fR); +.PP + +The function \fBpcre_compile()\fR is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument \fIpattern\fR. A pointer to a single block of memory +that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled +code and related data. The \fBpcre\fR type is defined for the returned block; +this is a typedef for a structure whose contents are not externally defined. It +is up to the caller to free the memory when it is no longer required. + +Although the compiled code of a PCRE regex is relocatable, that is, it does not +depend on memory location, the complete \fBpcre\fR data block is not +fully relocatable, because it contains a copy of the \fItableptr\fR argument, +which is an address (see below). + +The \fIoptions\fR argument contains independent bits that affect the +compilation. It should be zero if no options are required. Some of the options, +in particular, those that are compatible with Perl, can also be set and unset +from within the pattern (see the detailed description of regular expressions +in the \fBpcrepattern\fR documentation). For these options, the contents of the +\fIoptions\fR argument specifies their initial settings at the start of +compilation and execution. The PCRE_ANCHORED option can be set at the time of +matching as well as at compile time. + +If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately. +Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns +NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual +error message. The offset from the start of the pattern to the character where +the error was discovered is placed in the variable pointed to by +\fIerroffset\fR, which must not be NULL. If it is, an immediate error is given. + +If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of +character tables which are built when it is compiled, using the default C +locale. Otherwise, \fItableptr\fR must be the result of a call to +\fBpcre_maketables()\fR. See the section on locale support below. + +This code fragment shows a typical straightforward call to \fBpcre_compile()\fR: + + pcre *re; + const char *error; + int erroffset; + re = pcre_compile( + "^A.*Z", /* the pattern */ + 0, /* default options */ + &error, /* for error message */ + &erroffset, /* for error offset */ + NULL); /* use default character tables */ + +The following option bits are defined: + + PCRE_ANCHORED + +If this bit is set, the pattern is forced to be "anchored", that is, it is +constrained to match only at the first matching point in the string which is +being searched (the "subject string"). This effect can also be achieved by +appropriate constructs in the pattern itself, which is the only way to do it in +Perl. + + PCRE_CASELESS + +If this bit is set, letters in the pattern match both upper and lower case +letters. It is equivalent to Perl's /i option, and it can be changed within a +pattern by a (?i) option setting. + + PCRE_DOLLAR_ENDONLY + +If this bit is set, a dollar metacharacter in the pattern matches only at the +end of the subject string. Without this option, a dollar also matches +immediately before the final character if it is a newline (but not before any +other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is +set. There is no equivalent to this option in Perl, and no way to set it within +a pattern. + + PCRE_DOTALL + +If this bit is set, a dot metacharater in the pattern matches all characters, +including newlines. Without it, newlines are excluded. This option is +equivalent to Perl's /s option, and it can be changed within a pattern by a +(?s) option setting. A negative class such as [^a] always matches a newline +character, independent of the setting of this option. + + PCRE_EXTENDED + +If this bit is set, whitespace data characters in the pattern are totally +ignored except when escaped or inside a character class. Whitespace does not +include the VT character (code 11). In addition, characters between an +unescaped # outside a character class and the next newline character, +inclusive, are also ignored. This is equivalent to Perl's /x option, and it can +be changed within a pattern by a (?x) option setting. + +This option makes it possible to include comments inside complicated patterns. +Note, however, that this applies only to data characters. Whitespace characters +may never appear within special character sequences in a pattern, for example +within the sequence (?( which introduces a conditional subpattern. + + PCRE_EXTRA + +This option was invented in order to turn on additional functionality of PCRE +that is incompatible with Perl, but it is currently of very little use. When +set, any backslash in a pattern that is followed by a letter that has no +special meaning causes an error, thus reserving these combinations for future +expansion. By default, as in Perl, a backslash followed by a letter with no +special meaning is treated as a literal. There are at present no other features +controlled by this option. It can also be set by a (?X) option setting within a +pattern. + + PCRE_MULTILINE + +By default, PCRE treats the subject string as consisting of a single "line" of +characters (even if it actually contains several newlines). The "start of line" +metacharacter (^) matches only at the start of the string, while the "end of +line" metacharacter ($) matches only at the end of the string, or before a +terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as +Perl. + +When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs +match immediately following or immediately before any newline in the subject +string, respectively, as well as at the very start and end. This is equivalent +to Perl's /m option, and it can be changed within a pattern by a (?m) option +setting. If there are no "\\n" characters in a subject string, or no +occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. + + PCRE_NO_AUTO_CAPTURE + +If this option is set, it disables the use of numbered capturing parentheses in +the pattern. Any opening parenthesis that is not followed by ? behaves as if it +were followed by ?: but named parentheses can still be used for capturing (and +they acquire numbers in the usual way). There is no equivalent of this option +in Perl. + + PCRE_UNGREEDY + +This option inverts the "greediness" of the quantifiers so that they are not +greedy by default, but become greedy if followed by "?". It is not compatible +with Perl. It can also be set by a (?U) option setting within the pattern. + + PCRE_UTF8 + +This option causes PCRE to regard both the pattern and the subject as strings +of UTF-8 characters instead of single-byte character strings. However, it is +available only if PCRE has been built to include UTF-8 support. If not, the use +of this option provokes an error. Details of how this option changes the +behaviour of PCRE are given in the +.\" HTML <a href="pcre.html#utf8support"> +.\" </a> +section on UTF-8 support +.\" +in the main +.\" HREF +\fBpcre\fR +.\" +page. + + PCRE_NO_UTF8_CHECK + +When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is +automatically checked. If an invalid UTF-8 sequence of bytes is found, +\fBpcre_compile()\fR returns an error. If you already know that your pattern is +valid, and you want to skip this check for performance reasons, you can set the +PCRE_NO_UTF8_CHECK option. When it is set, the effect of passing an invalid +UTF-8 string as a pattern is undefined. It may cause your program to crash. +Note that there is a similar option for suppressing the checking of subject +strings passed to \fBpcre_exec()\fR. + + +.SH STUDYING A PATTERN +.rs +.sp +.B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR, +.ti +5n +.B const char **\fIerrptr\fR); +.PP +When a pattern is going to be used several times, it is worth spending more +time analyzing it in order to speed up the time taken for matching. The +function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first +argument. If studing the pattern produces additional information that will help +speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR +block, in which the \fIstudy_data\fR field points to the results of the study. + +The returned value from a \fBpcre_study()\fR can be passed directly to +\fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other +fields that can be set by the caller before the block is passed; these are +described below. If studying the pattern does not produce any additional +information, \fBpcre_study()\fR returns NULL. In that circumstance, if the +calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it +must set up its own \fBpcre_extra\fR block. + +The second argument contains option bits. At present, no options are defined +for \fBpcre_study()\fR, and this argument should always be zero. + +The third argument for \fBpcre_study()\fR is a pointer for an error message. If +studying succeeds (even if no data is returned), the variable it points to is +set to NULL. Otherwise it points to a textual error message. You should +therefore test the error pointer for NULL after calling \fBpcre_study()\fR, to +be sure that it has run successfully. + +This is a typical call to \fBpcre_study\fR(): + + pcre_extra *pe; + pe = pcre_study( + re, /* result of pcre_compile() */ + 0, /* no options exist */ + &error); /* set to NULL or points to a message */ + +At present, studying a pattern is useful only for non-anchored patterns that do +not have a single fixed starting character. A bitmap of possible starting +characters is created. + +.\" HTML <a name="localesupport"></a> +.SH LOCALE SUPPORT +.rs +.sp +PCRE handles caseless matching, and determines whether characters are letters, +digits, or whatever, by reference to a set of tables. When running in UTF-8 +mode, this applies only to characters with codes less than 256. The library +contains a default set of tables that is created in the default C locale when +PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR +is NULL, and is sufficient for many applications. + +An alternative set of tables can, however, be supplied. Such tables are built +by calling the \fBpcre_maketables()\fR function, which has no arguments, in the +relevant locale. The result can then be passed to \fBpcre_compile()\fR as often +as necessary. For example, to build and use tables that are appropriate for the +French locale (where accented characters with codes greater than 128 are +treated as letters), the following code could be used: + + setlocale(LC_CTYPE, "fr"); + tables = pcre_maketables(); + re = pcre_compile(..., tables); + +The tables are built in memory that is obtained via \fBpcre_malloc\fR. The +pointer that is passed to \fBpcre_compile\fR is saved with the compiled +pattern, and the same tables are used via this pointer by \fBpcre_study()\fR +and \fBpcre_exec()\fR. Thus, for any single pattern, compilation, studying and +matching all happen in the same locale, but different patterns can be compiled +in different locales. It is the caller's responsibility to ensure that the +memory containing the tables remains available for as long as it is needed. + +.SH INFORMATION ABOUT A PATTERN +.rs +.sp +.B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," +.ti +5n +.B int \fIwhat\fR, void *\fIwhere\fR); +.PP +The \fBpcre_fullinfo()\fR function returns information about a compiled +pattern. It replaces the obsolete \fBpcre_info()\fR function, which is +nevertheless retained for backwards compability (and is documented below). + +The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled +pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if +the pattern was not studied. The third argument specifies which piece of +information is required, and the fourth argument is a pointer to a variable +to receive the data. The yield of the function is zero for success, or one of +the following negative numbers: + + PCRE_ERROR_NULL the argument \fIcode\fR was NULL + the argument \fIwhere\fR was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + PCRE_ERROR_BADOPTION the value of \fIwhat\fR was invalid + +Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the +compiled pattern: + + int rc; + unsigned long int length; + rc = pcre_fullinfo( + re, /* result of pcre_compile() */ + pe, /* result of pcre_study(), or NULL */ + PCRE_INFO_SIZE, /* what is required */ + &length); /* where to put the data */ + +The possible values for the third argument are defined in \fBpcre.h\fR, and are +as follows: + + PCRE_INFO_BACKREFMAX + +Return the number of the highest back reference in the pattern. The fourth +argument should point to an \fBint\fR variable. Zero is returned if there are +no back references. + + PCRE_INFO_CAPTURECOUNT + +Return the number of capturing subpatterns in the pattern. The fourth argument +should point to an \fbint\fR variable. + + PCRE_INFO_FIRSTBYTE + +Return information about the first byte of any matched string, for a +non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the +old name is still recognized for backwards compatibility.) + +If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote), +it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either + +(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch +starts with "^", or + +(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set +(if it were set, the pattern would be anchored), + +-1 is returned, indicating that the pattern matches only at the start of a +subject string or after any newline within the string. Otherwise -2 is +returned. For anchored patterns, -2 is returned. + + PCRE_INFO_FIRSTTABLE + +If the pattern was studied, and this resulted in the construction of a 256-bit +table indicating a fixed set of bytes for the first byte in any matching +string, a pointer to the table is returned. Otherwise NULL is returned. The +fourth argument should point to an \fBunsigned char *\fR variable. + + PCRE_INFO_LASTLITERAL + +Return the value of the rightmost literal byte that must exist in any matched +string, other than at its start, if such a byte has been recorded. The fourth +argument should point to an \fBint\fR variable. If there is no such byte, -1 is +returned. For anchored patterns, a last literal byte is recorded only if it +follows something of variable length. For example, for the pattern +/^a\\d+z\\d+/ the returned value is "z", but for /^a\\dz\\d/ the returned value +is -1. + + PCRE_INFO_NAMECOUNT + PCRE_INFO_NAMEENTRYSIZE + PCRE_INFO_NAMETABLE + +PCRE supports the use of named as well as numbered capturing parentheses. The +names are just an additional way of identifying the parentheses, which still +acquire a number. A caller that wants to extract data from a named subpattern +must convert the name to a number in order to access the correct pointers in +the output vector (described with \fBpcre_exec()\fR below). In order to do +this, it must first use these three values to obtain the name-to-number mapping +table for the pattern. + +The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives +the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each +entry; both of these return an \fBint\fR value. The entry size depends on the +length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first +entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry +are the number of the capturing parenthesis, most significant byte first. The +rest of the entry is the corresponding name, zero terminated. The names are in +alphabetical order. For example, consider the following pattern (assume +PCRE_EXTENDED is set, so white space - including newlines - is ignored): + + (?P<date> (?P<year>(\\d\\d)?\\d\\d) - + (?P<month>\\d\\d) - (?P<day>\\d\\d) ) + +There are four named subpatterns, so the table has four entries, and each entry +in the table is eight bytes long. The table is as follows, with non-printing +bytes shows in hex, and undefined bytes shown as ??: + + 00 01 d a t e 00 ?? + 00 05 d a y 00 ?? ?? + 00 04 m o n t h 00 + 00 02 y e a r 00 ?? + +When writing code to extract data from named subpatterns, remember that the +length of each entry may be different for each compiled pattern. + + PCRE_INFO_OPTIONS + +Return a copy of the options with which the pattern was compiled. The fourth +argument should point to an \fBunsigned long int\fR variable. These option bits +are those specified in the call to \fBpcre_compile()\fR, modified by any +top-level option settings within the pattern itself. + +A pattern is automatically anchored by PCRE if all of its top-level +alternatives begin with one of the following: + + ^ unless PCRE_MULTILINE is set + \\A always + \\G always + .* if PCRE_DOTALL is set and there are no back + references to the subpattern in which .* appears + +For such patterns, the PCRE_ANCHORED bit is set in the options returned by +\fBpcre_fullinfo()\fR. + + PCRE_INFO_SIZE + +Return the size of the compiled pattern, that is, the value that was passed as +the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to +place the compiled data. The fourth argument should point to a \fBsize_t\fR +variable. + + PCRE_INFO_STUDYSIZE + +Returns the size of the data block pointed to by the \fIstudy_data\fR field in +a \fBpcre_extra\fR block. That is, it is the value that was passed to +\fBpcre_malloc()\fR when PCRE was getting memory into which to place the data +created by \fBpcre_study()\fR. The fourth argument should point to a +\fBsize_t\fR variable. + +.SH OBSOLETE INFO FUNCTION +.rs +.sp +.B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int +.B *\fIfirstcharptr\fR); +.PP +The \fBpcre_info()\fR function is now obsolete because its interface is too +restrictive to return all the available data about a compiled pattern. New +programs should use \fBpcre_fullinfo()\fR instead. The yield of +\fBpcre_info()\fR is the number of capturing subpatterns, or one of the +following negative numbers: + + PCRE_ERROR_NULL the argument \fIcode\fR was NULL + PCRE_ERROR_BADMAGIC the "magic number" was not found + +If the \fIoptptr\fR argument is not NULL, a copy of the options with which the +pattern was compiled is placed in the integer it points to (see +PCRE_INFO_OPTIONS above). + +If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL, +it is used to pass back information about the first character of any matched +string (see PCRE_INFO_FIRSTBYTE above). + +.SH MATCHING A PATTERN +.rs +.sp +.B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," +.ti +5n +.B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR, +.ti +5n +.B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR); +.PP +The function \fBpcre_exec()\fR is called to match a subject string against a +pre-compiled pattern, which is passed in the \fIcode\fR argument. If the +pattern has been studied, the result of the study should be passed in the +\fIextra\fR argument. + +Here is an example of a simple call to \fBpcre_exec()\fR: + + int rc; + int ovector[30]; + rc = pcre_exec( + re, /* result of pcre_compile() */ + NULL, /* we didn't study the pattern */ + "some string", /* the subject string */ + 11, /* the length of the subject string */ + 0, /* start at offset 0 in the subject */ + 0, /* default options */ + ovector, /* vector for substring information */ + 30); /* number of elements in the vector */ + +If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR +data block. The \fBpcre_study()\fR function returns such a block (when it +doesn't return NULL), but you can also create one for yourself, and pass +additional information in it. The fields in the block are as follows: + + unsigned long int \fIflags\fR; + void *\fIstudy_data\fR; + unsigned long int \fImatch_limit\fR; + void *\fIcallout_data\fR; + +The \fIflags\fR field is a bitmap that specifies which of the other fields +are set. The flag bits are: + + PCRE_EXTRA_STUDY_DATA + PCRE_EXTRA_MATCH_LIMIT + PCRE_EXTRA_CALLOUT_DATA + +Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the +\fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with +the appropriate flag bit. You should not set this yourself, but you can add to +the block by setting the other fields. + +The \fImatch_limit\fR field provides a means of preventing PCRE from using up a +vast amount of resources when running patterns that are not going to match, +but which have a very large number of possibilities in their search trees. The +classic example is the use of nested unlimited repeats. Internally, PCRE uses a +function called \fBmatch()\fR which it calls repeatedly (sometimes +recursively). The limit is imposed on the number of times this function is +called during a match, which has the effect of limiting the amount of recursion +and backtracking that can take place. For patterns that are not anchored, the +count starts from zero for each position in the subject string. + +The default limit for the library can be set when PCRE is built; the default +default is 10 million, which handles all but the most extreme cases. You can +reduce the default by suppling \fBpcre_exec()\fR with a \fRpcre_extra\fR block +in which \fImatch_limit\fR is set to a smaller value, and +PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fR field. If the limit is +exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT. + +The \fIpcre_callout\fR field is used in conjunction with the "callout" feature, +which is described in the \fBpcrecallout\fR documentation. + +The PCRE_ANCHORED option can be passed in the \fIoptions\fR argument, whose +unused bits must be zero. This limits \fBpcre_exec()\fR to matching at the +first matching position. However, if a pattern was compiled with PCRE_ANCHORED, +or turned out to be anchored by virtue of its contents, it cannot be made +unachored at matching time. + +When PCRE_UTF8 was set at compile time, the validity of the subject as a UTF-8 +string is automatically checked, and the value of \fIstartoffset\fR is also +checked to ensure that it points to the start of a UTF-8 character. If an +invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fR returns the error +PCRE_ERROR_BADUTF8. If \fIstartoffset\fR contains an invalid value, +PCRE_ERROR_BADUTF8_OFFSET is returned. + +If you already know that your subject is valid, and you want to skip these +checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when +calling \fBpcre_exec()\fR. You might want to do this for the second and +subsequent calls to \fBpcre_exec()\fR if you are making repeated calls to find +all the matches in a single subject string. However, you should be sure that +the value of \fIstartoffset\fR points to the start of a UTF-8 character. When +PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8 string as a +subject, or a value of \fIstartoffset\fR that does not point to the start of a +UTF-8 character, is undefined. Your program may crash. + +There are also three further options that can be set only at matching time: + + PCRE_NOTBOL + +The first character of the string is not the beginning of a line, so the +circumflex metacharacter should not match before it. Setting this without +PCRE_MULTILINE (at compile time) causes circumflex never to match. + + PCRE_NOTEOL + +The end of the string is not the end of a line, so the dollar metacharacter +should not match it nor (except in multiline mode) a newline immediately before +it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never +to match. + + PCRE_NOTEMPTY + +An empty string is not considered to be a valid match if this option is set. If +there are alternatives in the pattern, they are tried. If all the alternatives +match the empty string, the entire match fails. For example, if the pattern + + a?b? + +is applied to a string not beginning with "a" or "b", it matches the empty +string at the start of the subject. With PCRE_NOTEMPTY set, this match is not +valid, so PCRE searches further into the string for occurrences of "a" or "b". + +Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case +of a pattern match of the empty string within its \fBsplit()\fR function, and +when using the /g modifier. It is possible to emulate Perl's behaviour after +matching a null string by first trying the match again at the same offset with +PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see +below) and trying an ordinary match again. + +The subject string is passed to \fBpcre_exec()\fR as a pointer in +\fIsubject\fR, a length in \fIlength\fR, and a starting byte offset in +\fIstartoffset\fR. Unlike the pattern string, the subject may contain binary +zero bytes. When the starting offset is zero, the search for a match starts at +the beginning of the subject, and this is by far the most common case. + +If the pattern was compiled with the PCRE_UTF8 option, the subject must be a +sequence of bytes that is a valid UTF-8 string, and the starting offset must +point to the beginning of a UTF-8 character. If an invalid UTF-8 string or +offset is passed, an error (either PCRE_ERROR_BADUTF8 or +PCRE_ERROR_BADUTF8_OFFSET) is returned, unless the option PCRE_NO_UTF8_CHECK is +set, in which case PCRE's behaviour is not defined. + +A non-zero starting offset is useful when searching for another match in the +same subject by calling \fBpcre_exec()\fR again after a previous success. +Setting \fIstartoffset\fR differs from just passing over a shortened string and +setting PCRE_NOTBOL in the case of a pattern that begins with any kind of +lookbehind. For example, consider the pattern + + \\Biss\\B + +which finds occurrences of "iss" in the middle of words. (\\B matches only if +the current position in the subject is not a word boundary.) When applied to +the string "Mississipi" the first call to \fBpcre_exec()\fR finds the first +occurrence. If \fBpcre_exec()\fR is called again with just the remainder of the +subject, namely "issipi", it does not match, because \\B is always false at the +start of the subject, which is deemed to be a word boundary. However, if +\fBpcre_exec()\fR is passed the entire string again, but with \fIstartoffset\fR +set to 4, it finds the second occurrence of "iss" because it is able to look +behind the starting point to discover that it is preceded by a letter. + +If a non-zero starting offset is passed when the pattern is anchored, one +attempt to match at the given offset is tried. This can only succeed if the +pattern does not require the match to be at the start of the subject. + +In general, a pattern matches a certain portion of the subject, and in +addition, further substrings from the subject may be picked out by parts of the +pattern. Following the usage in Jeffrey Friedl's book, this is called +"capturing" in what follows, and the phrase "capturing subpattern" is used for +a fragment of a pattern that picks out a substring. PCRE supports several other +kinds of parenthesized subpattern that do not cause substrings to be captured. + +Captured substrings are returned to the caller via a vector of integer offsets +whose address is passed in \fIovector\fR. The number of elements in the vector +is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass +back captured substrings, each substring using a pair of integers. The +remaining third of the vector is used as workspace by \fBpcre_exec()\fR while +matching capturing subpatterns, and is not available for passing back +information. The length passed in \fIovecsize\fR should always be a multiple of +three. If it is not, it is rounded down. + +When a match has been successful, information about captured substrings is +returned in pairs of integers, starting at the beginning of \fIovector\fR, and +continuing up to two-thirds of its length at the most. The first element of a +pair is set to the offset of the first character in a substring, and the second +is set to the offset of the first character after the end of a substring. The +first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the +subject string matched by the entire pattern. The next pair is used for the +first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR +is the number of pairs that have been set. If there are no capturing +subpatterns, the return value from a successful match is 1, indicating that +just the first pair of offsets has been set. + +Some convenience functions are provided for extracting the captured substrings +as separate strings. These are described in the following section. + +It is possible for an capturing subpattern number \fIn+1\fR to match some +part of the subject when subpattern \fIn\fR has not been used at all. For +example, if the string "abc" is matched against the pattern (a|(z))(bc) +subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset +values corresponding to the unused subpattern are set to -1. + +If a capturing subpattern is matched repeatedly, it is the last portion of the +string that it matched that gets returned. + +If the vector is too small to hold all the captured substrings, it is used as +far as possible (up to two-thirds of its length), and the function returns a +value of zero. In particular, if the substring offsets are not of interest, +\fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and +\fIovecsize\fR as zero. However, if the pattern contains back references and +the \fIovector\fR isn't big enough to remember the related substrings, PCRE has +to get additional memory for use during matching. Thus it is usually advisable +to supply an \fIovector\fR. + +Note that \fBpcre_info()\fR can be used to find out how many capturing +subpatterns there are in a compiled pattern. The smallest size for +\fIovector\fR that will allow for \fIn\fR captured substrings, in addition to +the offsets of the substring matched by the whole pattern, is (\fIn\fR+1)*3. + +If \fBpcre_exec()\fR fails, it returns a negative number. The following are +defined in the header file: + + PCRE_ERROR_NOMATCH (-1) + +The subject string did not match the pattern. + + PCRE_ERROR_NULL (-2) + +Either \fIcode\fR or \fIsubject\fR was passed as NULL, or \fIovector\fR was +NULL and \fIovecsize\fR was not zero. + + PCRE_ERROR_BADOPTION (-3) + +An unrecognized bit was set in the \fIoptions\fR argument. + + PCRE_ERROR_BADMAGIC (-4) + +PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch +the case when it is passed a junk pointer. This is the error it gives when the +magic number isn't present. + + PCRE_ERROR_UNKNOWN_NODE (-5) + +While running the pattern match, an unknown item was encountered in the +compiled pattern. This error could be caused by a bug in PCRE or by overwriting +of the compiled pattern. + + PCRE_ERROR_NOMEMORY (-6) + +If a pattern contains back references, but the \fIovector\fR that is passed to +\fBpcre_exec()\fR is not big enough to remember the referenced substrings, PCRE +gets a block of memory at the start of matching to use for this purpose. If the +call via \fBpcre_malloc()\fR fails, this error is given. The memory is freed at +the end of matching. + + PCRE_ERROR_NOSUBSTRING (-7) + +This error is used by the \fBpcre_copy_substring()\fR, +\fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see +below). It is never returned by \fBpcre_exec()\fR. + + PCRE_ERROR_MATCHLIMIT (-8) + +The recursion and backtracking limit, as specified by the \fImatch_limit\fR +field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the +description above. + + PCRE_ERROR_CALLOUT (-9) + +This error is never generated by \fBpcre_exec()\fR itself. It is provided for +use by callout functions that want to yield a distinctive error code. See the +\fBpcrecallout\fR documentation for details. + + PCRE_ERROR_BADUTF8 (-10) + +A string that contains an invalid UTF-8 byte sequence was passed as a subject. + + PCRE_ERROR_BADUTF8_OFFSET (-11) + +The UTF-8 byte sequence that was passed as a subject was valid, but the value +of \fIstartoffset\fR did not point to the beginning of a UTF-8 character. + +.SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER +.rs +.sp +.B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR, +.ti +5n +.B int \fIbuffersize\fR); +.PP +.br +.B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, int \fIstringnumber\fR, +.ti +5n +.B const char **\fIstringptr\fR); +.PP +.br +.B int pcre_get_substring_list(const char *\fIsubject\fR, +.ti +5n +.B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);" +.PP +Captured substrings can be accessed directly by using the offsets returned by +\fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions +\fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and +\fBpcre_get_substring_list()\fR are provided for extracting captured substrings +as new, separate, zero-terminated strings. These functions identify substrings +by number. The next section describes functions for extracting named +substrings. A substring that contains a binary zero is correctly extracted and +has a further zero added on the end, but the result is not, of course, +a C string. + +The first three arguments are the same for all three of these functions: +\fIsubject\fR is the subject string which has just been successfully matched, +\fIovector\fR is a pointer to the vector of integer offsets that was passed to +\fBpcre_exec()\fR, and \fIstringcount\fR is the number of substrings that were +captured by the match, including the substring that matched the entire regular +expression. This is the value returned by \fBpcre_exec\fR if it is greater than +zero. If \fBpcre_exec()\fR returned zero, indicating that it ran out of space +in \fIovector\fR, the value passed as \fIstringcount\fR should be the size of +the vector divided by three. + +The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR +extract a single substring, whose number is given as \fIstringnumber\fR. A +value of zero extracts the substring that matched the entire pattern, while +higher values extract the captured substrings. For \fBpcre_copy_substring()\fR, +the string is placed in \fIbuffer\fR, whose length is given by +\fIbuffersize\fR, while for \fBpcre_get_substring()\fR a new block of memory is +obtained via \fBpcre_malloc\fR, and its address is returned via +\fIstringptr\fR. The yield of the function is the length of the string, not +including the terminating zero, or one of + + PCRE_ERROR_NOMEMORY (-6) + +The buffer was too small for \fBpcre_copy_substring()\fR, or the attempt to get +memory failed for \fBpcre_get_substring()\fR. + + PCRE_ERROR_NOSUBSTRING (-7) + +There is no substring whose number is \fIstringnumber\fR. + +The \fBpcre_get_substring_list()\fR function extracts all available substrings +and builds a list of pointers to them. All this is done in a single block of +memory which is obtained via \fBpcre_malloc\fR. The address of the memory block +is returned via \fIlistptr\fR, which is also the start of the list of string +pointers. The end of the list is marked by a NULL pointer. The yield of the +function is zero if all went well, or + + PCRE_ERROR_NOMEMORY (-6) + +if the attempt to get the memory block failed. + +When any of these functions encounter a substring that is unset, which can +happen when capturing subpattern number \fIn+1\fR matches some part of the +subject, but subpattern \fIn\fR has not been used at all, they return an empty +string. This can be distinguished from a genuine zero-length substring by +inspecting the appropriate offset in \fIovector\fR, which is negative for unset +substrings. + +The two convenience functions \fBpcre_free_substring()\fR and +\fBpcre_free_substring_list()\fR can be used to free the memory returned by +a previous call of \fBpcre_get_substring()\fR or +\fBpcre_get_substring_list()\fR, respectively. They do nothing more than call +the function pointed to by \fBpcre_free\fR, which of course could be called +directly from a C program. However, PCRE is used in some situations where it is +linked via a special interface to another programming language which cannot use +\fBpcre_free\fR directly; it is for these cases that the functions are +provided. + +.SH EXTRACTING CAPTURED SUBSTRINGS BY NAME +.rs +.sp +.B int pcre_copy_named_substring(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, const char *\fIstringname\fR, +.ti +5n +.B char *\fIbuffer\fR, int \fIbuffersize\fR); +.PP +.br +.B int pcre_get_stringnumber(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIname\fR); +.PP +.br +.B int pcre_get_named_substring(const pcre *\fIcode\fR, +.ti +5n +.B const char *\fIsubject\fR, int *\fIovector\fR, +.ti +5n +.B int \fIstringcount\fR, const char *\fIstringname\fR, +.ti +5n +.B const char **\fIstringptr\fR); +.PP +To extract a substring by name, you first have to find associated number. This +can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the +compiled pattern, and the second is the name. For example, for this pattern + + ab(?<xxx>\\d+)... + +the number of the subpattern called "xxx" is 1. Given the number, you can then +extract the substring directly, or use one of the functions described in the +previous section. For convenience, there are also two functions that do the +whole job. + +Most of the arguments of \fIpcre_copy_named_substring()\fR and +\fIpcre_get_named_substring()\fR are the same as those for the functions that +extract by number, and so are not re-described here. There are just two +differences. + +First, instead of a substring number, a substring name is given. Second, there +is an extra argument, given at the start, which is a pointer to the compiled +pattern. This is needed in order to gain access to the name-to-number +translation table. + +These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they +then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as +appropriate. + +.in 0 +Last updated: 09 December 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcrebuild.3 b/external-libs/pcre/doc/pcrebuild.3 new file mode 100644 index 00000000..a91782c0 --- /dev/null +++ b/external-libs/pcre/doc/pcrebuild.3 @@ -0,0 +1,145 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH PCRE BUILD-TIME OPTIONS +.rs +.sp +This document describes the optional features of PCRE that can be selected when +the library is compiled. They are all selected, or deselected, by providing +options to the \fBconfigure\fR script which is run before the \fBmake\fR +command. The complete list of options for \fBconfigure\fR (which includes the +standard ones such as the selection of the installation directory) can be +obtained by running + + ./configure --help + +The following sections describe certain options whose names begin with --enable +or --disable. These settings specify changes to the defaults for the +\fBconfigure\fR command. Because of the way that \fBconfigure\fR works, +--enable and --disable always come in pairs, so the complementary option always +exists as well, but as it specifies the default, it is not described. + +.SH UTF-8 SUPPORT +.rs +.sp +To build PCRE with support for UTF-8 character strings, add + + --enable-utf8 + +to the \fBconfigure\fR command. Of itself, this does not make PCRE treat +strings as UTF-8. As well as compiling PCRE with this option, you also have +have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fR +function. + +.SH CODE VALUE OF NEWLINE +.rs +.sp +By default, PCRE treats character 10 (linefeed) as the newline character. This +is the normal newline character on Unix-like systems. You can compile PCRE to +use character 13 (carriage return) instead by adding + + --enable-newline-is-cr + +to the \fBconfigure\fR command. For completeness there is also a +--enable-newline-is-lf option, which explicitly specifies linefeed as the +newline character. + +.SH BUILDING SHARED AND STATIC LIBRARIES +.rs +.sp +The PCRE building process uses \fBlibtool\fR to build both shared and static +Unix libraries by default. You can suppress one of these by adding one of + + --disable-shared + --disable-static + +to the \fBconfigure\fR command, as required. + +.SH POSIX MALLOC USAGE +.rs +.sp +When PCRE is called through the POSIX interface (see the \fBpcreposix\fR +documentation), additional working storage is required for holding the pointers +to capturing substrings because PCRE requires three integers per substring, +whereas the POSIX interface provides only two. If the number of expected +substrings is small, the wrapper function uses space on the stack, because this +is faster than using \fBmalloc()\fR for each call. The default threshold above +which the stack is no longer used is 10; it can be changed by adding a setting +such as + + --with-posix-malloc-threshold=20 + +to the \fBconfigure\fR command. + +.SH LIMITING PCRE RESOURCE USAGE +.rs +.sp +Internally, PCRE has a function called \fBmatch()\fR which it calls repeatedly +(possibly recursively) when performing a matching operation. By limiting the +number of times this function may be called, a limit can be placed on the +resources used by a single call to \fBpcre_exec()\fR. The limit can be changed +at run time, as described in the \fBpcreapi\fR documentation. The default is 10 +million, but this can be changed by adding a setting such as + + --with-match-limit=500000 + +to the \fBconfigure\fR command. + +.SH HANDLING VERY LARGE PATTERNS +.rs +.sp +Within a compiled pattern, offset values are used to point from one part to +another (for example, from an opening parenthesis to an alternation +metacharacter). By default two-byte values are used for these offsets, leading +to a maximum size for a compiled pattern of around 64K. This is sufficient to +handle all but the most gigantic patterns. Nevertheless, some people do want to +process enormous patterns, so it is possible to compile PCRE to use three-byte +or four-byte offsets by adding a setting such as + + --with-link-size=3 + +to the \fBconfigure\fR command. The value given must be 2, 3, or 4. Using +longer offsets slows down the operation of PCRE because it has to load +additional bytes when handling them. + +If you build PCRE with an increased link size, test 2 (and test 5 if you are +using UTF-8) will fail. Part of the output of these tests is a representation +of the compiled pattern, and this changes with the link size. + +.SH AVOIDING EXCESSIVE STACK USAGE +.rs +.sp +PCRE implements backtracking while matching by making recursive calls to an +internal function called \fBmatch()\fR. In environments where the size of the +stack is limited, this can severely limit PCRE's operation. (The Unix +environment does not usually suffer from this problem.) An alternative approach +that uses memory from the heap to remember data, instead of using recursive +function calls, has been implemented to work round this problem. If you want to +build a version of PCRE that works this way, add + + --disable-stack-for-recursion + +to the \fBconfigure\fR command. With this configuration, PCRE will use the +\fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR variables to call memory +management functions. Separate functions are provided because the usage is very +predictable: the block sizes requested are always the same, and the blocks are +always freed in reverse order. A calling program might be able to implement +optimized functions that perform better than the standard \fBmalloc()\fR and +\fBfree()\fR functions. PCRE runs noticeably more slowly when built in this +way. + +.SH USING EBCDIC CODE +.rs +.sp +PCRE assumes by default that it will run in an environment where the character +code is ASCII (or UTF-8, which is a superset of ASCII). PCRE can, however, be +compiled to run in an EBCDIC environment by adding + + --enable-ebcdic + +to the \fBconfigure\fR command. + +.in 0 +Last updated: 09 December 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcrecallout.3 b/external-libs/pcre/doc/pcrecallout.3 new file mode 100644 index 00000000..bfbb66b2 --- /dev/null +++ b/external-libs/pcre/doc/pcrecallout.3 @@ -0,0 +1,92 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH PCRE CALLOUTS +.rs +.sp +.B int (*pcre_callout)(pcre_callout_block *); +.PP +PCRE provides a feature called "callout", which is a means of temporarily +passing control to the caller of PCRE in the middle of pattern matching. The +caller of PCRE provides an external function by putting its entry point in the +global variable \fIpcre_callout\fR. By default, this variable contains NULL, +which disables all calling out. + +Within a regular expression, (?C) indicates the points at which the external +function is to be called. Different callout points can be identified by putting +a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: + + (?C1)\dabc(?C2)def + +During matching, when PCRE reaches a callout point (and \fIpcre_callout\fR is +set), the external function is called. Its only argument is a pointer to a +\fBpcre_callout\fR block. This contains the following variables: + + int \fIversion\fR; + int \fIcallout_number\fR; + int *\fIoffset_vector\fR; + const char *\fIsubject\fR; + int \fIsubject_length\fR; + int \fIstart_match\fR; + int \fIcurrent_position\fR; + int \fIcapture_top\fR; + int \fIcapture_last\fR; + void *\fIcallout_data\fR; + +The \fIversion\fR field is an integer containing the version number of the +block format. The current version is zero. The version number may change in +future if additional fields are added, but the intention is never to remove any +of the existing fields. + +The \fIcallout_number\fR field contains the number of the callout, as compiled +into the pattern (that is, the number after ?C). + +The \fIoffset_vector\fR field is a pointer to the vector of offsets that was +passed by the caller to \fBpcre_exec()\fR. The contents can be inspected in +order to extract substrings that have been matched so far, in the same way as +for extracting substrings after a match has completed. + +The \fIsubject\fR and \fIsubject_length\fR fields contain copies the values +that were passed to \fBpcre_exec()\fR. + +The \fIstart_match\fR field contains the offset within the subject at which the +current match attempt started. If the pattern is not anchored, the callout +function may be called several times for different starting points. + +The \fIcurrent_position\fR field contains the offset within the subject of the +current match pointer. + +The \fIcapture_top\fR field contains one more than the number of the highest +numbered captured substring so far. If no substrings have been captured, +the value of \fIcapture_top\fR is one. + +The \fIcapture_last\fR field contains the number of the most recently captured +substring. + +The \fIcallout_data\fR field contains a value that is passed to +\fBpcre_exec()\fR by the caller specifically so that it can be passed back in +callouts. It is passed in the \fIpcre_callout\fR field of the \fBpcre_extra\fR +data structure. If no such data was passed, the value of \fIcallout_data\fR in +a \fBpcre_callout\fR block is NULL. There is a description of the +\fBpcre_extra\fR structure in the \fBpcreapi\fR documentation. + + +.SH RETURN VALUES +.rs +.sp +The callout function returns an integer. If the value is zero, matching +proceeds as normal. If the value is greater than zero, matching fails at the +current point, but backtracking to test other possibilities goes ahead, just as +if a lookahead assertion had failed. If the value is less than zero, the match +is abandoned, and \fBpcre_exec()\fR returns the value. + +Negative values should normally be chosen from the set of PCRE_ERROR_xxx +values. In particular, PCRE_ERROR_NOMATCH forces a standard "no match" failure. +The error number PCRE_ERROR_CALLOUT is reserved for use by callout functions; +it will never be used by PCRE itself. + +.in 0 +Last updated: 21 January 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcrecompat.3 b/external-libs/pcre/doc/pcrecompat.3 new file mode 100644 index 00000000..e358f607 --- /dev/null +++ b/external-libs/pcre/doc/pcrecompat.3 @@ -0,0 +1,107 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH DIFFERENCES FROM PERL +.rs +.sp +This document describes the differences in the ways that PCRE and Perl handle +regular expressions. The differences described here are with respect to Perl +5.8. + +1. PCRE does not have full UTF-8 support. Details of what it does have are +given in the +.\" HTML <a href="pcre.html#utf8support"> +.\" </a> +section on UTF-8 support +.\" +in the main +.\" HREF +\fBpcre\fR +.\" +page. + +2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl permits +them, but they do not mean what you might think. For example, (?!a){3} does +not assert that the next three characters are not "a". It just asserts that the +next character is not "a" three times. + +3. Capturing subpatterns that occur inside negative lookahead assertions are +counted, but their entries in the offsets vector are never set. Perl sets its +numerical variables from any such patterns that are matched before the +assertion fails to match something (thereby succeeding), but only if the +negative lookahead assertion contains just one branch. + +4. Though binary zero characters are supported in the subject string, they are +not allowed in a pattern string because it is passed as a normal C string, +terminated by zero. The escape sequence "\\0" can be used in the pattern to +represent a binary zero. + +5. The following Perl escape sequences are not supported: \\l, \\u, \\L, +\\U, \\P, \\p, \\N, and \\X. In fact these are implemented by Perl's general +string-handling and are not part of its pattern matching engine. If any of +these are encountered by PCRE, an error is generated. + +6. PCRE does support the \\Q...\\E escape for quoting substrings. Characters in +between are treated as literals. This is slightly different from Perl in that $ +and @ are also handled as literals inside the quotes. In Perl, they cause +variable interpolation (but of course PCRE does not have variables). Note the +following examples: + + Pattern PCRE matches Perl matches + + \\Qabc$xyz\\E abc$xyz abc followed by the + contents of $xyz + \\Qabc\\$xyz\\E abc\\$xyz abc\\$xyz + \\Qabc\\E\\$\\Qxyz\\E abc$xyz abc$xyz + +The \\Q...\\E sequence is recognized both inside and outside character classes. + +7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) +constructions. However, there is some experimental support for recursive +patterns using the non-Perl items (?R), (?number) and (?P>name). Also, the PCRE +"callout" feature allows an external function to be called during pattern +matching. + +8. There are some differences that are concerned with the settings of captured +strings when part of a pattern is repeated. For example, matching "aba" against +the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b". + +9. PCRE provides some extensions to the Perl regular expression facilities: + +(a) Although lookbehind assertions must match fixed length strings, each +alternative branch of a lookbehind assertion can match a different length of +string. Perl requires them all to have the same length. + +(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ +meta-character matches only at the very end of the string. + +(c) If PCRE_EXTRA is set, a backslash followed by a letter with no special +meaning is faulted. + +(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is +inverted, that is, by default they are not greedy, but if followed by a +question mark they are. + +(e) PCRE_ANCHORED can be used to force a pattern to be tried only at the first +matching position in the subject string. + +(f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAPTURE +options for \fBpcre_exec()\fR have no Perl equivalents. + +(g) The (?R), (?number), and (?P>name) constructs allows for recursive pattern +matching (Perl can do this using the (?p{code}) construct, which PCRE cannot +support.) + +(h) PCRE supports named capturing substrings, using the Python syntax. + +(i) PCRE supports the possessive quantifier "++" syntax, taken from Sun's Java +package. + +(j) The (R) condition, for testing recursion, is a PCRE extension. + +(k) The callout facility is PCRE-specific. + +.in 0 +Last updated: 09 December 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcregrep.1 b/external-libs/pcre/doc/pcregrep.1 new file mode 100644 index 00000000..c40dc054 --- /dev/null +++ b/external-libs/pcre/doc/pcregrep.1 @@ -0,0 +1,130 @@ +.TH PCREGREP 1 +.SH NAME +pcregrep - a grep with Perl-compatible regular expressions. +.SH SYNOPSIS +.B pcregrep [-Vcfhilnrsuvx] [long options] [pattern] [file1 file2 ...] + +.SH DESCRIPTION +.rs +.sp +\fBpcregrep\fR searches files for character patterns, in the same way as other +grep commands do, but it uses the PCRE regular expression library to support +patterns that are compatible with the regular expressions of Perl 5. See +.\" HREF +\fBpcrepattern\fR +.\" +for a full description of syntax and semantics of the regular expressions that +PCRE supports. + +A pattern must be specified on the command line unless the \fB-f\fR option is +used (see below). + +If no files are specified, \fBpcregrep\fR reads the standard input. By default, +each line that matches the pattern is copied to the standard output, and if +there is more than one file, the file name is printed before each line of +output. However, there are options that can change how \fBpcregrep\fR behaves. + +Lines are limited to BUFSIZ characters. BUFSIZ is defined in \fB<stdio.h>\fR. +The newline character is removed from the end of each line before it is matched +against the pattern. + +.SH OPTIONS +.rs +.sp +.TP 10 +\fB-V\fR +Write the version number of the PCRE library being used to the standard error +stream. +.TP +\fB-c\fR +Do not print individual lines; instead just print a count of the number of +lines that would otherwise have been printed. If several files are given, a +count is printed for each of them. +.TP +\fB-f\fR\fIfilename\fR +Read a number of patterns from the file, one per line, and match all of them +against each line of input. A line is output if any of the patterns match it. +When \fB-f\fR is used, no pattern is taken from the command line; all arguments +are treated as file names. There is a maximum of 100 patterns. Trailing white +space is removed, and blank lines are ignored. An empty file contains no +patterns and therefore matches nothing. +.TP +\fB-h\fR +Suppress printing of filenames when searching multiple files. +.TP +\fB-i\fR +Ignore upper/lower case distinctions during comparisons. +.TP +\fB-l\fR +Instead of printing lines from the files, just print the names of the files +containing lines that would have been printed. Each file name is printed +once, on a separate line. +.TP +\fB-n\fR +Precede each line by its line number in the file. +.TP +\fB-r\fR +If any file is a directory, recursively scan the files it contains. Without +\fB-r\fR a directory is scanned as a normal file. +.TP +\fB-s\fR +Work silently, that is, display nothing except error messages. +The exit status indicates whether any matches were found. +.TP +\fB-u\fR +Operate in UTF-8 mode. This option is available only if PCRE has been compiled +with UTF-8 support. Both the pattern and each subject line are assumed to be +valid strings of UTF-8 characters. +.TP +\fB-v\fR +Invert the sense of the match, so that lines which do \fInot\fR match the +pattern are now the ones that are found. +.TP +\fB-x\fR +Force the pattern to be anchored (it must start matching at the beginning of +the line) and in addition, require it to match the entire line. This is +equivalent to having ^ and $ characters at the start and end of each +alternative branch in the regular expression. + +.SH LONG OPTIONS +.rs +.sp +Long forms of all the options are available, as in GNU grep. They are shown in +the following table: + + -c --count + -h --no-filename + -i --ignore-case + -l --files-with-matches + -n --line-number + -r --recursive + -s --no-messages + -u --utf-8 + -V --version + -v --invert-match + -x --line-regex + -x --line-regexp + +In addition, --file=\fIfilename\fR is equivalent to -f\fIfilename\fR, and +--help shows the list of options and then exits. + +.SH DIAGNOSTICS +.rs +.sp +Exit status is 0 if any matches were found, 1 if no matches were found, and 2 +for syntax errors or inacessible files (even if matches were found). + + +.SH AUTHOR +.rs +.sp +Philip Hazel <ph10@cam.ac.uk> +.br +University Computing Service +.br +Cambridge CB2 3QG, England. + +.in 0 +Last updated: 03 February 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcregrep.txt b/external-libs/pcre/doc/pcregrep.txt new file mode 100644 index 00000000..aae8928f --- /dev/null +++ b/external-libs/pcre/doc/pcregrep.txt @@ -0,0 +1,124 @@ +PCREGREP(1) PCREGREP(1) + + + +NAME + pcregrep - a grep with Perl-compatible regular expressions. + +SYNOPSIS + pcregrep [-Vcfhilnrsuvx] [long options] [pattern] [file1 file2 ...] + + +DESCRIPTION + + pcregrep searches files for character patterns, in the same way as + other grep commands do, but it uses the PCRE regular expression library + to support patterns that are compatible with the regular expressions of + Perl 5. See pcrepattern for a full description of syntax and semantics + of the regular expressions that PCRE supports. + + A pattern must be specified on the command line unless the -f option is + used (see below). + + If no files are specified, pcregrep reads the standard input. By + default, each line that matches the pattern is copied to the standard + output, and if there is more than one file, the file name is printed + before each line of output. However, there are options that can change + how pcregrep behaves. + + Lines are limited to BUFSIZ characters. BUFSIZ is defined in <stdio.h>. + The newline character is removed from the end of each line before it is + matched against the pattern. + + +OPTIONS + + + -V Write the version number of the PCRE library being used to + the standard error stream. + + -c Do not print individual lines; instead just print a count of + the number of lines that would otherwise have been printed. + If several files are given, a count is printed for each of + them. + + -ffilename + Read a number of patterns from the file, one per line, and + match all of them against each line of input. A line is out- + put if any of the patterns match it. When -f is used, no + pattern is taken from the command line; all arguments are + treated as file names. There is a maximum of 100 patterns. + Trailing white space is removed, and blank lines are ignored. + An empty file contains no patterns and therefore matches + nothing. + + -h Suppress printing of filenames when searching multiple files. + + -i Ignore upper/lower case distinctions during comparisons. + + -l Instead of printing lines from the files, just print the + names of the files containing lines that would have been + printed. Each file name is printed once, on a separate line. + + -n Precede each line by its line number in the file. + + -r If any file is a directory, recursively scan the files it + contains. Without -r a directory is scanned as a normal file. + + -s Work silently, that is, display nothing except error mes- + sages. The exit status indicates whether any matches were + found. + + -u Operate in UTF-8 mode. This option is available only if PCRE + has been compiled with UTF-8 support. Both the pattern and + each subject line are assumed to be valid strings of UTF-8 + characters. + + -v Invert the sense of the match, so that lines which do not + match the pattern are now the ones that are found. + + -x Force the pattern to be anchored (it must start matching at + the beginning of the line) and in addition, require it to + match the entire line. This is equivalent to having ^ and $ + characters at the start and end of each alternative branch in + the regular expression. + + +LONG OPTIONS + + Long forms of all the options are available, as in GNU grep. They are + shown in the following table: + + -c --count + -h --no-filename + -i --ignore-case + -l --files-with-matches + -n --line-number + -r --recursive + -s --no-messages + -u --utf-8 + -V --version + -v --invert-match + -x --line-regex + -x --line-regexp + + In addition, --file=filename is equivalent to -ffilename, and --help + shows the list of options and then exits. + + +DIAGNOSTICS + + Exit status is 0 if any matches were found, 1 if no matches were found, + and 2 for syntax errors or inacessible files (even if matches were + found). + + + +AUTHOR + + Philip Hazel <ph10@cam.ac.uk> + University Computing Service + Cambridge CB2 3QG, England. + +Last updated: 03 February 2003 +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcrepattern.3 b/external-libs/pcre/doc/pcrepattern.3 new file mode 100644 index 00000000..101aa311 --- /dev/null +++ b/external-libs/pcre/doc/pcrepattern.3 @@ -0,0 +1,1231 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH PCRE REGULAR EXPRESSION DETAILS +.rs +.sp +The syntax and semantics of the regular expressions supported by PCRE are +described below. Regular expressions are also described in the Perl +documentation and in a number of other books, some of which have copious +examples. Jeffrey Friedl's "Mastering Regular Expressions", published by +O'Reilly, covers them in great detail. The description here is intended as +reference documentation. + +The basic operation of PCRE is on strings of bytes. However, there is also +support for UTF-8 character strings. To use this support you must build PCRE to +include UTF-8 support, and then call \fBpcre_compile()\fR with the PCRE_UTF8 +option. How this affects the pattern matching is mentioned in several places +below. There is also a summary of UTF-8 features in the +.\" HTML <a href="pcre.html#utf8support"> +.\" </a> +section on UTF-8 support +.\" +in the main +.\" HREF +\fBpcre\fR +.\" +page. + +A regular expression is a pattern that is matched against a subject string from +left to right. Most characters stand for themselves in a pattern, and match the +corresponding characters in the subject. As a trivial example, the pattern + + The quick brown fox + +matches a portion of a subject string that is identical to itself. The power of +regular expressions comes from the ability to include alternatives and +repetitions in the pattern. These are encoded in the pattern by the use of +\fImeta-characters\fR, which do not stand for themselves but instead are +interpreted in some special way. + +There are two different sets of meta-characters: those that are recognized +anywhere in the pattern except within square brackets, and those that are +recognized in square brackets. Outside square brackets, the meta-characters are +as follows: + + \\ general escape character with several uses + ^ assert start of string (or line, in multiline mode) + $ assert end of string (or line, in multiline mode) + . match any character except newline (by default) + [ start character class definition + | start of alternative branch + ( start subpattern + ) end subpattern + ? extends the meaning of ( + also 0 or 1 quantifier + also quantifier minimizer + * 0 or more quantifier + + 1 or more quantifier + also "possessive quantifier" + { start min/max quantifier + +Part of a pattern that is in square brackets is called a "character class". In +a character class the only meta-characters are: + + \\ general escape character + ^ negate the class, but only if the first character + - indicates character range + [ POSIX character class (only if followed by POSIX + syntax) + ] terminates the character class + +The following sections describe the use of each of the meta-characters. + +.SH BACKSLASH +.rs +.sp +The backslash character has several uses. Firstly, if it is followed by a +non-alphameric character, it takes away any special meaning that character may +have. This use of backslash as an escape character applies both inside and +outside character classes. + +For example, if you want to match a * character, you write \\* in the pattern. +This escaping action applies whether or not the following character would +otherwise be interpreted as a meta-character, so it is always safe to precede a +non-alphameric with backslash to specify that it stands for itself. In +particular, if you want to match a backslash, you write \\\\. + +If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the +pattern (other than in a character class) and characters between a # outside +a character class and the next newline character are ignored. An escaping +backslash can be used to include a whitespace or # character as part of the +pattern. + +If you want to remove the special meaning from a sequence of characters, you +can do so by putting them between \\Q and \\E. This is different from Perl in +that $ and @ are handled as literals in \\Q...\\E sequences in PCRE, whereas in +Perl, $ and @ cause variable interpolation. Note the following examples: + + Pattern PCRE matches Perl matches + + \\Qabc$xyz\\E abc$xyz abc followed by the + contents of $xyz + \\Qabc\\$xyz\\E abc\\$xyz abc\\$xyz + \\Qabc\\E\\$\\Qxyz\\E abc$xyz abc$xyz + +The \\Q...\\E sequence is recognized both inside and outside character classes. + +A second use of backslash provides a way of encoding non-printing characters +in patterns in a visible manner. There is no restriction on the appearance of +non-printing characters, apart from the binary zero that terminates a pattern, +but when a pattern is being prepared by text editing, it is usually easier to +use one of the following escape sequences than the binary character it +represents: + + \\a alarm, that is, the BEL character (hex 07) + \\cx "control-x", where x is any character + \\e escape (hex 1B) + \\f formfeed (hex 0C) + \\n newline (hex 0A) + \\r carriage return (hex 0D) + \\t tab (hex 09) + \\ddd character with octal code ddd, or backreference + \\xhh character with hex code hh + \\x{hhh..} character with hex code hhh... (UTF-8 mode only) + +The precise effect of \\cx is as follows: if x is a lower case letter, it +is converted to upper case. Then bit 6 of the character (hex 40) is inverted. +Thus \\cz becomes hex 1A, but \\c{ becomes hex 3B, while \\c; becomes hex +7B. + +After \\x, from zero to two hexadecimal digits are read (letters can be in +upper or lower case). In UTF-8 mode, any number of hexadecimal digits may +appear between \\x{ and }, but the value of the character code must be less +than 2**31 (that is, the maximum hexadecimal value is 7FFFFFFF). If characters +other than hexadecimal digits appear between \\x{ and }, or if there is no +terminating }, this form of escape is not recognized. Instead, the initial +\\x will be interpreted as a basic hexadecimal escape, with no following +digits, giving a byte whose value is zero. + +Characters whose value is less than 256 can be defined by either of the two +syntaxes for \\x when PCRE is in UTF-8 mode. There is no difference in the +way they are handled. For example, \\xdc is exactly the same as \\x{dc}. + +After \\0 up to two further octal digits are read. In both cases, if there +are fewer than two digits, just those that are present are used. Thus the +sequence \\0\\x\\07 specifies two binary zeros followed by a BEL character +(code value 7). Make sure you supply two digits after the initial zero if the +character that follows is itself an octal digit. + +The handling of a backslash followed by a digit other than 0 is complicated. +Outside a character class, PCRE reads it and any following digits as a decimal +number. If the number is less than 10, or if there have been at least that many +previous capturing left parentheses in the expression, the entire sequence is +taken as a \fIback reference\fR. A description of how this works is given +later, following the discussion of parenthesized subpatterns. + +Inside a character class, or if the decimal number is greater than 9 and there +have not been that many capturing subpatterns, PCRE re-reads up to three octal +digits following the backslash, and generates a single byte from the least +significant 8 bits of the value. Any subsequent digits stand for themselves. +For example: + + \\040 is another way of writing a space + \\40 is the same, provided there are fewer than 40 + previous capturing subpatterns + \\7 is always a back reference + \\11 might be a back reference, or another way of + writing a tab + \\011 is always a tab + \\0113 is a tab followed by the character "3" + \\113 might be a back reference, otherwise the + character with octal code 113 + \\377 might be a back reference, otherwise + the byte consisting entirely of 1 bits + \\81 is either a back reference, or a binary zero + followed by the two characters "8" and "1" + +Note that octal values of 100 or greater must not be introduced by a leading +zero, because no more than three octal digits are ever read. + +All the sequences that define a single byte value or a single UTF-8 character +(in UTF-8 mode) can be used both inside and outside character classes. In +addition, inside a character class, the sequence \\b is interpreted as the +backspace character (hex 08). Outside a character class it has a different +meaning (see below). + +The third use of backslash is for specifying generic character types: + + \\d any decimal digit + \\D any character that is not a decimal digit + \\s any whitespace character + \\S any character that is not a whitespace character + \\w any "word" character + \\W any "non-word" character + +Each pair of escape sequences partitions the complete set of characters into +two disjoint sets. Any given character matches one, and only one, of each pair. + +In UTF-8 mode, characters with values greater than 255 never match \\d, \\s, or +\\w, and always match \\D, \\S, and \\W. + +For compatibility with Perl, \\s does not match the VT character (code 11). +This makes it different from the the POSIX "space" class. The \\s characters +are HT (9), LF (10), FF (12), CR (13), and space (32). + +A "word" character is any letter or digit or the underscore character, that is, +any character which can be part of a Perl "word". The definition of letters and +digits is controlled by PCRE's character tables, and may vary if locale- +specific matching is taking place (see +.\" HTML <a href="pcreapi.html#localesupport"> +.\" </a> +"Locale support" +.\" +in the +.\" HREF +\fBpcreapi\fR +.\" +page). For example, in the "fr" (French) locale, some character codes greater +than 128 are used for accented letters, and these are matched by \\w. + +These character type sequences can appear both inside and outside character +classes. They each match one character of the appropriate type. If the current +matching point is at the end of the subject string, all of them fail, since +there is no character to match. + +The fourth use of backslash is for certain simple assertions. An assertion +specifies a condition that has to be met at a particular point in a match, +without consuming any characters from the subject string. The use of +subpatterns for more complicated assertions is described below. The backslashed +assertions are + + \\b matches at a word boundary + \\B matches when not at a word boundary + \\A matches at start of subject + \\Z matches at end of subject or before newline at end + \\z matches at end of subject + \\G matches at first matching position in subject + +These assertions may not appear in character classes (but note that \\b has a +different meaning, namely the backspace character, inside a character class). + +A word boundary is a position in the subject string where the current character +and the previous character do not both match \\w or \\W (i.e. one matches +\\w and the other matches \\W), or the start or end of the string if the +first or last character matches \\w, respectively. + +The \\A, \\Z, and \\z assertions differ from the traditional circumflex and +dollar (described below) in that they only ever match at the very start and end +of the subject string, whatever options are set. Thus, they are independent of +multiline mode. + +They are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options. If the +\fIstartoffset\fR argument of \fBpcre_exec()\fR is non-zero, indicating that +matching is to start at a point other than the beginning of the subject, \\A +can never match. The difference between \\Z and \\z is that \\Z matches before +a newline that is the last character of the string as well as at the end of the +string, whereas \\z matches only at the end. + +The \\G assertion is true only when the current matching position is at the +start point of the match, as specified by the \fIstartoffset\fR argument of +\fBpcre_exec()\fR. It differs from \\A when the value of \fIstartoffset\fR is +non-zero. By calling \fBpcre_exec()\fR multiple times with appropriate +arguments, you can mimic Perl's /g option, and it is in this kind of +implementation where \\G can be useful. + +Note, however, that PCRE's interpretation of \\G, as the start of the current +match, is subtly different from Perl's, which defines it as the end of the +previous match. In Perl, these can be different when the previously matched +string was empty. Because PCRE does just one match at a time, it cannot +reproduce this behaviour. + +If all the alternatives of a pattern begin with \\G, the expression is anchored +to the starting match position, and the "anchored" flag is set in the compiled +regular expression. + +.SH CIRCUMFLEX AND DOLLAR +.rs +.sp +Outside a character class, in the default matching mode, the circumflex +character is an assertion which is true only if the current matching point is +at the start of the subject string. If the \fIstartoffset\fR argument of +\fBpcre_exec()\fR is non-zero, circumflex can never match if the PCRE_MULTILINE +option is unset. Inside a character class, circumflex has an entirely different +meaning (see below). + +Circumflex need not be the first character of the pattern if a number of +alternatives are involved, but it should be the first thing in each alternative +in which it appears if the pattern is ever to match that branch. If all +possible alternatives start with a circumflex, that is, if the pattern is +constrained to match only at the start of the subject, it is said to be an +"anchored" pattern. (There are also other constructs that can cause a pattern +to be anchored.) + +A dollar character is an assertion which is true only if the current matching +point is at the end of the subject string, or immediately before a newline +character that is the last character in the string (by default). Dollar need +not be the last character of the pattern if a number of alternatives are +involved, but it should be the last item in any branch in which it appears. +Dollar has no special meaning in a character class. + +The meaning of dollar can be changed so that it matches only at the very end of +the string, by setting the PCRE_DOLLAR_ENDONLY option at compile time. This +does not affect the \\Z assertion. + +The meanings of the circumflex and dollar characters are changed if the +PCRE_MULTILINE option is set. When this is the case, they match immediately +after and immediately before an internal newline character, respectively, in +addition to matching at the start and end of the subject string. For example, +the pattern /^abc$/ matches the subject string "def\\nabc" in multiline mode, +but not otherwise. Consequently, patterns that are anchored in single line mode +because all branches start with ^ are not anchored in multiline mode, and a +match for circumflex is possible when the \fIstartoffset\fR argument of +\fBpcre_exec()\fR is non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if +PCRE_MULTILINE is set. + +Note that the sequences \\A, \\Z, and \\z can be used to match the start and +end of the subject in both modes, and if all branches of a pattern start with +\\A it is always anchored, whether PCRE_MULTILINE is set or not. + +.SH FULL STOP (PERIOD, DOT) +.rs +.sp +Outside a character class, a dot in the pattern matches any one character in +the subject, including a non-printing character, but not (by default) newline. +In UTF-8 mode, a dot matches any UTF-8 character, which might be more than one +byte long, except (by default) for newline. If the PCRE_DOTALL option is set, +dots match newlines as well. The handling of dot is entirely independent of the +handling of circumflex and dollar, the only relationship being that they both +involve newline characters. Dot has no special meaning in a character class. + +.SH MATCHING A SINGLE BYTE +.rs +.sp +Outside a character class, the escape sequence \\C matches any one byte, both +in and out of UTF-8 mode. Unlike a dot, it always matches a newline. The +feature is provided in Perl in order to match individual bytes in UTF-8 mode. +Because it breaks up UTF-8 characters into individual bytes, what remains in +the string may be a malformed UTF-8 string. For this reason it is best avoided. + +PCRE does not allow \\C to appear in lookbehind assertions (see below), because +in UTF-8 mode it makes it impossible to calculate the length of the lookbehind. + +.SH SQUARE BRACKETS +.rs +.sp +An opening square bracket introduces a character class, terminated by a closing +square bracket. A closing square bracket on its own is not special. If a +closing square bracket is required as a member of the class, it should be the +first data character in the class (after an initial circumflex, if present) or +escaped with a backslash. + +A character class matches a single character in the subject. In UTF-8 mode, the +character may occupy more than one byte. A matched character must be in the set +of characters defined by the class, unless the first character in the class +definition is a circumflex, in which case the subject character must not be in +the set defined by the class. If a circumflex is actually required as a member +of the class, ensure it is not the first character, or escape it with a +backslash. + +For example, the character class [aeiou] matches any lower case vowel, while +[^aeiou] matches any character that is not a lower case vowel. Note that a +circumflex is just a convenient notation for specifying the characters which +are in the class by enumerating those that are not. It is not an assertion: it +still consumes a character from the subject string, and fails if the current +pointer is at the end of the string. + +In UTF-8 mode, characters with values greater than 255 can be included in a +class as a literal string of bytes, or by using the \\x{ escaping mechanism. + +When caseless matching is set, any letters in a class represent both their +upper case and lower case versions, so for example, a caseless [aeiou] matches +"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a +caseful version would. PCRE does not support the concept of case for characters +with values greater than 255. + +The newline character is never treated in any special way in character classes, +whatever the setting of the PCRE_DOTALL or PCRE_MULTILINE options is. A class +such as [^a] will always match a newline. + +The minus (hyphen) character can be used to specify a range of characters in a +character class. For example, [d-m] matches any letter between d and m, +inclusive. If a minus character is required in a class, it must be escaped with +a backslash or appear in a position where it cannot be interpreted as +indicating a range, typically as the first or last character in the class. + +It is not possible to have the literal character "]" as the end character of a +range. A pattern such as [W-]46] is interpreted as a class of two characters +("W" and "-") followed by a literal string "46]", so it would match "W46]" or +"-46]". However, if the "]" is escaped with a backslash it is interpreted as +the end of range, so [W-\\]46] is interpreted as a single class containing a +range followed by two separate characters. The octal or hexadecimal +representation of "]" can also be used to end a range. + +Ranges operate in the collating sequence of character values. They can also be +used for characters specified numerically, for example [\\000-\\037]. In UTF-8 +mode, ranges can include characters whose values are greater than 255, for +example [\\x{100}-\\x{2ff}]. + +If a range that includes letters is used when caseless matching is set, it +matches the letters in either case. For example, [W-c] is equivalent to +[][\\^_`wxyzabc], matched caselessly, and if character tables for the "fr" +locale are in use, [\\xc8-\\xcb] matches accented E characters in both cases. + +The character types \\d, \\D, \\s, \\S, \\w, and \\W may also appear in a +character class, and add the characters that they match to the class. For +example, [\\dABCDEF] matches any hexadecimal digit. A circumflex can +conveniently be used with the upper case character types to specify a more +restricted set of characters than the matching lower case type. For example, +the class [^\\W_] matches any letter or digit, but not underscore. + +All non-alphameric characters other than \\, -, ^ (at the start) and the +terminating ] are non-special in character classes, but it does no harm if they +are escaped. + +.SH POSIX CHARACTER CLASSES +.rs +.sp +Perl supports the POSIX notation for character classes, which uses names +enclosed by [: and :] within the enclosing square brackets. PCRE also supports +this notation. For example, + + [01[:alpha:]%] + +matches "0", "1", any alphabetic character, or "%". The supported class names +are + + alnum letters and digits + alpha letters + ascii character codes 0 - 127 + blank space or tab only + cntrl control characters + digit decimal digits (same as \\d) + graph printing characters, excluding space + lower lower case letters + print printing characters, including space + punct printing characters, excluding letters and digits + space white space (not quite the same as \\s) + upper upper case letters + word "word" characters (same as \\w) + xdigit hexadecimal digits + +The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), and +space (32). Notice that this list includes the VT character (code 11). This +makes "space" different to \\s, which does not include VT (for Perl +compatibility). + +The name "word" is a Perl extension, and "blank" is a GNU extension from Perl +5.8. Another Perl extension is negation, which is indicated by a ^ character +after the colon. For example, + + [12[:^digit:]] + +matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the POSIX +syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not +supported, and an error is given if they are encountered. + +In UTF-8 mode, characters with values greater than 255 do not match any of +the POSIX character classes. + +.SH VERTICAL BAR +.rs +.sp +Vertical bar characters are used to separate alternative patterns. For example, +the pattern + + gilbert|sullivan + +matches either "gilbert" or "sullivan". Any number of alternatives may appear, +and an empty alternative is permitted (matching the empty string). +The matching process tries each alternative in turn, from left to right, +and the first one that succeeds is used. If the alternatives are within a +subpattern (defined below), "succeeds" means matching the rest of the main +pattern as well as the alternative in the subpattern. + +.SH INTERNAL OPTION SETTING +.rs +.sp +The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and +PCRE_EXTENDED options can be changed from within the pattern by a sequence of +Perl option letters enclosed between "(?" and ")". The option letters are + + i for PCRE_CASELESS + m for PCRE_MULTILINE + s for PCRE_DOTALL + x for PCRE_EXTENDED + +For example, (?im) sets caseless, multiline matching. It is also possible to +unset these options by preceding the letter with a hyphen, and a combined +setting and unsetting such as (?im-sx), which sets PCRE_CASELESS and +PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, is also +permitted. If a letter appears both before and after the hyphen, the option is +unset. + +When an option change occurs at top level (that is, not inside subpattern +parentheses), the change applies to the remainder of the pattern that follows. +If the change is placed right at the start of a pattern, PCRE extracts it into +the global options (and it will therefore show up in data extracted by the +\fBpcre_fullinfo()\fR function). + +An option change within a subpattern affects only that part of the current +pattern that follows it, so + + (a(?i)b)c + +matches abc and aBc and no other strings (assuming PCRE_CASELESS is not used). +By this means, options can be made to have different settings in different +parts of the pattern. Any changes made in one alternative do carry on +into subsequent branches within the same subpattern. For example, + + (a(?i)b|c) + +matches "ab", "aB", "c", and "C", even though when matching "C" the first +branch is abandoned before the option setting. This is because the effects of +option settings happen at compile time. There would be some very weird +behaviour otherwise. + +The PCRE-specific options PCRE_UNGREEDY and PCRE_EXTRA can be changed in the +same way as the Perl-compatible options by using the characters U and X +respectively. The (?X) flag setting is special in that it must always occur +earlier in the pattern than any of the additional features it turns on, even +when it is at top level. It is best put at the start. + +.SH SUBPATTERNS +.rs +.sp +Subpatterns are delimited by parentheses (round brackets), which can be nested. +Marking part of a pattern as a subpattern does two things: + +1. It localizes a set of alternatives. For example, the pattern + + cat(aract|erpillar|) + +matches one of the words "cat", "cataract", or "caterpillar". Without the +parentheses, it would match "cataract", "erpillar" or the empty string. + +2. It sets up the subpattern as a capturing subpattern (as defined above). +When the whole pattern matches, that portion of the subject string that matched +the subpattern is passed back to the caller via the \fIovector\fR argument of +\fBpcre_exec()\fR. Opening parentheses are counted from left to right (starting +from 1) to obtain the numbers of the capturing subpatterns. + +For example, if the string "the red king" is matched against the pattern + + the ((red|white) (king|queen)) + +the captured substrings are "red king", "red", and "king", and are numbered 1, +2, and 3, respectively. + +The fact that plain parentheses fulfil two functions is not always helpful. +There are often times when a grouping subpattern is required without a +capturing requirement. If an opening parenthesis is followed by a question mark +and a colon, the subpattern does not do any capturing, and is not counted when +computing the number of any subsequent capturing subpatterns. For example, if +the string "the white queen" is matched against the pattern + + the ((?:red|white) (king|queen)) + +the captured substrings are "white queen" and "queen", and are numbered 1 and +2. The maximum number of capturing subpatterns is 65535, and the maximum depth +of nesting of all subpatterns, both capturing and non-capturing, is 200. + +As a convenient shorthand, if any option settings are required at the start of +a non-capturing subpattern, the option letters may appear between the "?" and +the ":". Thus the two patterns + + (?i:saturday|sunday) + (?:(?i)saturday|sunday) + +match exactly the same set of strings. Because alternative branches are tried +from left to right, and options are not reset until the end of the subpattern +is reached, an option setting in one branch does affect subsequent branches, so +the above patterns match "SUNDAY" as well as "Saturday". + +.SH NAMED SUBPATTERNS +.rs +.sp +Identifying capturing parentheses by number is simple, but it can be very hard +to keep track of the numbers in complicated regular expressions. Furthermore, +if an expression is modified, the numbers may change. To help with the +difficulty, PCRE supports the naming of subpatterns, something that Perl does +not provide. The Python syntax (?P<name>...) is used. Names consist of +alphanumeric characters and underscores, and must be unique within a pattern. + +Named capturing parentheses are still allocated numbers as well as names. The +PCRE API provides function calls for extracting the name-to-number translation +table from a compiled pattern. For further details see the +.\" HREF +\fBpcreapi\fR +.\" +documentation. + +.SH REPETITION +.rs +.sp +Repetition is specified by quantifiers, which can follow any of the following +items: + + a literal data character + the . metacharacter + the \\C escape sequence + escapes such as \\d that match single characters + a character class + a back reference (see next section) + a parenthesized subpattern (unless it is an assertion) + +The general repetition quantifier specifies a minimum and maximum number of +permitted matches, by giving the two numbers in curly brackets (braces), +separated by a comma. The numbers must be less than 65536, and the first must +be less than or equal to the second. For example: + + z{2,4} + +matches "zz", "zzz", or "zzzz". A closing brace on its own is not a special +character. If the second number is omitted, but the comma is present, there is +no upper limit; if the second number and the comma are both omitted, the +quantifier specifies an exact number of required matches. Thus + + [aeiou]{3,} + +matches at least 3 successive vowels, but may match many more, while + + \\d{8} + +matches exactly 8 digits. An opening curly bracket that appears in a position +where a quantifier is not allowed, or one that does not match the syntax of a +quantifier, is taken as a literal character. For example, {,6} is not a +quantifier, but a literal string of four characters. + +In UTF-8 mode, quantifiers apply to UTF-8 characters rather than to individual +bytes. Thus, for example, \\x{100}{2} matches two UTF-8 characters, each of +which is represented by a two-byte sequence. + +The quantifier {0} is permitted, causing the expression to behave as if the +previous item and the quantifier were not present. + +For convenience (and historical compatibility) the three most common +quantifiers have single-character abbreviations: + + * is equivalent to {0,} + + is equivalent to {1,} + ? is equivalent to {0,1} + +It is possible to construct infinite loops by following a subpattern that can +match no characters with a quantifier that has no upper limit, for example: + + (a?)* + +Earlier versions of Perl and PCRE used to give an error at compile time for +such patterns. However, because there are cases where this can be useful, such +patterns are now accepted, but if any repetition of the subpattern does in fact +match no characters, the loop is forcibly broken. + +By default, the quantifiers are "greedy", that is, they match as much as +possible (up to the maximum number of permitted times), without causing the +rest of the pattern to fail. The classic example of where this gives problems +is in trying to match comments in C programs. These appear between the +sequences /* and */ and within the sequence, individual * and / characters may +appear. An attempt to match C comments by applying the pattern + + /\\*.*\\*/ + +to the string + + /* first command */ not comment /* second comment */ + +fails, because it matches the entire string owing to the greediness of the .* +item. + +However, if a quantifier is followed by a question mark, it ceases to be +greedy, and instead matches the minimum number of times possible, so the +pattern + + /\\*.*?\\*/ + +does the right thing with the C comments. The meaning of the various +quantifiers is not otherwise changed, just the preferred number of matches. +Do not confuse this use of question mark with its use as a quantifier in its +own right. Because it has two uses, it can sometimes appear doubled, as in + + \\d??\\d + +which matches one digit by preference, but can match two if that is the only +way the rest of the pattern matches. + +If the PCRE_UNGREEDY option is set (an option which is not available in Perl), +the quantifiers are not greedy by default, but individual ones can be made +greedy by following them with a question mark. In other words, it inverts the +default behaviour. + +When a parenthesized subpattern is quantified with a minimum repeat count that +is greater than 1 or with a limited maximum, more store is required for the +compiled pattern, in proportion to the size of the minimum or maximum. + +If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent +to Perl's /s) is set, thus allowing the . to match newlines, the pattern is +implicitly anchored, because whatever follows will be tried against every +character position in the subject string, so there is no point in retrying the +overall match at any position after the first. PCRE normally treats such a +pattern as though it were preceded by \\A. + +In cases where it is known that the subject string contains no newlines, it is +worth setting PCRE_DOTALL in order to obtain this optimization, or +alternatively using ^ to indicate anchoring explicitly. + +However, there is one situation where the optimization cannot be used. When .* +is inside capturing parentheses that are the subject of a backreference +elsewhere in the pattern, a match at the start may fail, and a later one +succeed. Consider, for example: + + (.*)abc\\1 + +If the subject is "xyz123abc123" the match point is the fourth character. For +this reason, such a pattern is not implicitly anchored. + +When a capturing subpattern is repeated, the value captured is the substring +that matched the final iteration. For example, after + + (tweedle[dume]{3}\\s*)+ + +has matched "tweedledum tweedledee" the value of the captured substring is +"tweedledee". However, if there are nested capturing subpatterns, the +corresponding captured values may have been set in previous iterations. For +example, after + + /(a|(b))+/ + +matches "aba" the value of the second captured substring is "b". + +.SH ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS +.rs +.sp +With both maximizing and minimizing repetition, failure of what follows +normally causes the repeated item to be re-evaluated to see if a different +number of repeats allows the rest of the pattern to match. Sometimes it is +useful to prevent this, either to change the nature of the match, or to cause +it fail earlier than it otherwise might, when the author of the pattern knows +there is no point in carrying on. + +Consider, for example, the pattern \\d+foo when applied to the subject line + + 123456bar + +After matching all 6 digits and then failing to match "foo", the normal +action of the matcher is to try again with only 5 digits matching the \\d+ +item, and then with 4, and so on, before ultimately failing. "Atomic grouping" +(a term taken from Jeffrey Friedl's book) provides the means for specifying +that once a subpattern has matched, it is not to be re-evaluated in this way. + +If we use atomic grouping for the previous example, the matcher would give up +immediately on failing to match "foo" the first time. The notation is a kind of +special parenthesis, starting with (?> as in this example: + + (?>\\d+)foo + +This kind of parenthesis "locks up" the part of the pattern it contains once +it has matched, and a failure further into the pattern is prevented from +backtracking into it. Backtracking past it to previous items, however, works as +normal. + +An alternative description is that a subpattern of this type matches the string +of characters that an identical standalone pattern would match, if anchored at +the current point in the subject string. + +Atomic grouping subpatterns are not capturing subpatterns. Simple cases such as +the above example can be thought of as a maximizing repeat that must swallow +everything it can. So, while both \\d+ and \\d+? are prepared to adjust the +number of digits they match in order to make the rest of the pattern match, +(?>\\d+) can only match an entire sequence of digits. + +Atomic groups in general can of course contain arbitrarily complicated +subpatterns, and can be nested. However, when the subpattern for an atomic +group is just a single repeated item, as in the example above, a simpler +notation, called a "possessive quantifier" can be used. This consists of an +additional + character following a quantifier. Using this notation, the +previous example can be rewritten as + + \\d++bar + +Possessive quantifiers are always greedy; the setting of the PCRE_UNGREEDY +option is ignored. They are a convenient notation for the simpler forms of +atomic group. However, there is no difference in the meaning or processing of a +possessive quantifier and the equivalent atomic group. + +The possessive quantifier syntax is an extension to the Perl syntax. It +originates in Sun's Java package. + +When a pattern contains an unlimited repeat inside a subpattern that can itself +be repeated an unlimited number of times, the use of an atomic group is the +only way to avoid some failing matches taking a very long time indeed. The +pattern + + (\\D+|<\\d+>)*[!?] + +matches an unlimited number of substrings that either consist of non-digits, or +digits enclosed in <>, followed by either ! or ?. When it matches, it runs +quickly. However, if it is applied to + + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa + +it takes a long time before reporting failure. This is because the string can +be divided between the two repeats in a large number of ways, and all have to +be tried. (The example used [!?] rather than a single character at the end, +because both PCRE and Perl have an optimization that allows for fast failure +when a single character is used. They remember the last single character that +is required for a match, and fail early if it is not present in the string.) +If the pattern is changed to + + ((?>\\D+)|<\\d+>)*[!?] + +sequences of non-digits cannot be broken, and failure happens quickly. + +.SH BACK REFERENCES +.rs +.sp +Outside a character class, a backslash followed by a digit greater than 0 (and +possibly further digits) is a back reference to a capturing subpattern earlier +(that is, to its left) in the pattern, provided there have been that many +previous capturing left parentheses. + +However, if the decimal number following the backslash is less than 10, it is +always taken as a back reference, and causes an error only if there are not +that many capturing left parentheses in the entire pattern. In other words, the +parentheses that are referenced need not be to the left of the reference for +numbers less than 10. See the section entitled "Backslash" above for further +details of the handling of digits following a backslash. + +A back reference matches whatever actually matched the capturing subpattern in +the current subject string, rather than anything matching the subpattern +itself (see +.\" HTML <a href="#subpatternsassubroutines"> +.\" </a> +"Subpatterns as subroutines" +.\" +below for a way of doing that). So the pattern + + (sens|respons)e and \\1ibility + +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If caseful matching is in force at the time of the +back reference, the case of letters is relevant. For example, + + ((?i)rah)\\s+\\1 + +matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original +capturing subpattern is matched caselessly. + +Back references to named subpatterns use the Python syntax (?P=name). We could +rewrite the above example as follows: + + (?<p1>(?i)rah)\\s+(?P=p1) + +There may be more than one back reference to the same subpattern. If a +subpattern has not actually been used in a particular match, any back +references to it always fail. For example, the pattern + + (a|(bc))\\2 + +always fails if it starts to match "a" rather than "bc". Because there may be +many capturing parentheses in a pattern, all digits following the backslash are +taken as part of a potential back reference number. If the pattern continues +with a digit character, some delimiter must be used to terminate the back +reference. If the PCRE_EXTENDED option is set, this can be whitespace. +Otherwise an empty comment can be used. + +A back reference that occurs inside the parentheses to which it refers fails +when the subpattern is first used, so, for example, (a\\1) never matches. +However, such references can be useful inside repeated subpatterns. For +example, the pattern + + (a|b\\1)+ + +matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration of +the subpattern, the back reference matches the character string corresponding +to the previous iteration. In order for this to work, the pattern must be such +that the first iteration does not need to match the back reference. This can be +done using alternation, as in the example above, or by a quantifier with a +minimum of zero. + +.SH ASSERTIONS +.rs +.sp +An assertion is a test on the characters following or preceding the current +matching point that does not actually consume any characters. The simple +assertions coded as \\b, \\B, \\A, \\G, \\Z, \\z, ^ and $ are described above. +More complicated assertions are coded as subpatterns. There are two kinds: +those that look ahead of the current position in the subject string, and those +that look behind it. + +An assertion subpattern is matched in the normal way, except that it does not +cause the current matching position to be changed. Lookahead assertions start +with (?= for positive assertions and (?! for negative assertions. For example, + + \\w+(?=;) + +matches a word followed by a semicolon, but does not include the semicolon in +the match, and + + foo(?!bar) + +matches any occurrence of "foo" that is not followed by "bar". Note that the +apparently similar pattern + + (?!foo)bar + +does not find an occurrence of "bar" that is preceded by something other than +"foo"; it finds any occurrence of "bar" whatsoever, because the assertion +(?!foo) is always true when the next three characters are "bar". A +lookbehind assertion is needed to achieve this effect. + +If you want to force a matching failure at some point in a pattern, the most +convenient way to do it is with (?!) because an empty string always matches, so +an assertion that requires there not to be an empty string must always fail. + +Lookbehind assertions start with (?<= for positive assertions and (?<! for +negative assertions. For example, + + (?<!foo)bar + +does find an occurrence of "bar" that is not preceded by "foo". The contents of +a lookbehind assertion are restricted such that all the strings it matches must +have a fixed length. However, if there are several alternatives, they do not +all have to have the same fixed length. Thus + + (?<=bullock|donkey) + +is permitted, but + + (?<!dogs?|cats?) + +causes an error at compile time. Branches that match different length strings +are permitted only at the top level of a lookbehind assertion. This is an +extension compared with Perl (at least for 5.8), which requires all branches to +match the same length of string. An assertion such as + + (?<=ab(c|de)) + +is not permitted, because its single top-level branch can match two different +lengths, but it is acceptable if rewritten to use two top-level branches: + + (?<=abc|abde) + +The implementation of lookbehind assertions is, for each alternative, to +temporarily move the current position back by the fixed width and then try to +match. If there are insufficient characters before the current position, the +match is deemed to fail. + +PCRE does not allow the \\C escape (which matches a single byte in UTF-8 mode) +to appear in lookbehind assertions, because it makes it impossible to calculate +the length of the lookbehind. + +Atomic groups can be used in conjunction with lookbehind assertions to specify +efficient matching at the end of the subject string. Consider a simple pattern +such as + + abcd$ + +when applied to a long string that does not match. Because matching proceeds +from left to right, PCRE will look for each "a" in the subject and then see if +what follows matches the rest of the pattern. If the pattern is specified as + + ^.*abcd$ + +the initial .* matches the entire string at first, but when this fails (because +there is no following "a"), it backtracks to match all but the last character, +then all but the last two characters, and so on. Once again the search for "a" +covers the entire string, from right to left, so we are no better off. However, +if the pattern is written as + + ^(?>.*)(?<=abcd) + +or, equivalently, + + ^.*+(?<=abcd) + +there can be no backtracking for the .* item; it can match only the entire +string. The subsequent lookbehind assertion does a single test on the last four +characters. If it fails, the match fails immediately. For long strings, this +approach makes a significant difference to the processing time. + +Several assertions (of any sort) may occur in succession. For example, + + (?<=\\d{3})(?<!999)foo + +matches "foo" preceded by three digits that are not "999". Notice that each of +the assertions is applied independently at the same point in the subject +string. First there is a check that the previous three characters are all +digits, and then there is a check that the same three characters are not "999". +This pattern does \fInot\fR match "foo" preceded by six characters, the first +of which are digits and the last three of which are not "999". For example, it +doesn't match "123abcfoo". A pattern to do that is + + (?<=\\d{3}...)(?<!999)foo + +This time the first assertion looks at the preceding six characters, checking +that the first three are digits, and then the second assertion checks that the +preceding three characters are not "999". + +Assertions can be nested in any combination. For example, + + (?<=(?<!foo)bar)baz + +matches an occurrence of "baz" that is preceded by "bar" which in turn is not +preceded by "foo", while + + (?<=\\d{3}(?!999)...)foo + +is another pattern which matches "foo" preceded by three digits and any three +characters that are not "999". + +Assertion subpatterns are not capturing subpatterns, and may not be repeated, +because it makes no sense to assert the same thing several times. If any kind +of assertion contains capturing subpatterns within it, these are counted for +the purposes of numbering the capturing subpatterns in the whole pattern. +However, substring capturing is carried out only for positive assertions, +because it does not make sense for negative assertions. + +.SH CONDITIONAL SUBPATTERNS +.rs +.sp +It is possible to cause the matching process to obey a subpattern +conditionally or to choose between two alternative subpatterns, depending on +the result of an assertion, or whether a previous capturing subpattern matched +or not. The two possible forms of conditional subpattern are + + (?(condition)yes-pattern) + (?(condition)yes-pattern|no-pattern) + +If the condition is satisfied, the yes-pattern is used; otherwise the +no-pattern (if present) is used. If there are more than two alternatives in the +subpattern, a compile-time error occurs. + +There are three kinds of condition. If the text between the parentheses +consists of a sequence of digits, the condition is satisfied if the capturing +subpattern of that number has previously matched. The number must be greater +than zero. Consider the following pattern, which contains non-significant white +space to make it more readable (assume the PCRE_EXTENDED option) and to divide +it into three parts for ease of discussion: + + ( \\( )? [^()]+ (?(1) \\) ) + +The first part matches an optional opening parenthesis, and if that +character is present, sets it as the first captured substring. The second part +matches one or more characters that are not parentheses. The third part is a +conditional subpattern that tests whether the first set of parentheses matched +or not. If they did, that is, if subject started with an opening parenthesis, +the condition is true, and so the yes-pattern is executed and a closing +parenthesis is required. Otherwise, since no-pattern is not present, the +subpattern matches nothing. In other words, this pattern matches a sequence of +non-parentheses, optionally enclosed in parentheses. + +If the condition is the string (R), it is satisfied if a recursive call to the +pattern or subpattern has been made. At "top level", the condition is false. +This is a PCRE extension. Recursive patterns are described in the next section. + +If the condition is not a sequence of digits or (R), it must be an assertion. +This may be a positive or negative lookahead or lookbehind assertion. Consider +this pattern, again containing non-significant white space, and with the two +alternatives on the second line: + + (?(?=[^a-z]*[a-z]) + \\d{2}-[a-z]{3}-\\d{2} | \\d{2}-\\d{2}-\\d{2} ) + +The condition is a positive lookahead assertion that matches an optional +sequence of non-letters followed by a letter. In other words, it tests for the +presence of at least one letter in the subject. If a letter is found, the +subject is matched against the first alternative; otherwise it is matched +against the second. This pattern matches strings in one of the two forms +dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. + +.SH COMMENTS +.rs +.sp +The sequence (?# marks the start of a comment which continues up to the next +closing parenthesis. Nested parentheses are not permitted. The characters +that make up a comment play no part in the pattern matching at all. + +If the PCRE_EXTENDED option is set, an unescaped # character outside a +character class introduces a comment that continues up to the next newline +character in the pattern. + +.SH RECURSIVE PATTERNS +.rs +.sp +Consider the problem of matching a string in parentheses, allowing for +unlimited nested parentheses. Without the use of recursion, the best that can +be done is to use a pattern that matches up to some fixed depth of nesting. It +is not possible to handle an arbitrary nesting depth. Perl has provided an +experimental facility that allows regular expressions to recurse (amongst other +things). It does this by interpolating Perl code in the expression at run time, +and the code can refer to the expression itself. A Perl pattern to solve the +parentheses problem can be created like this: + + $re = qr{\\( (?: (?>[^()]+) | (?p{$re}) )* \\)}x; + +The (?p{...}) item interpolates Perl code at run time, and in this case refers +recursively to the pattern in which it appears. Obviously, PCRE cannot support +the interpolation of Perl code. Instead, it supports some special syntax for +recursion of the entire pattern, and also for individual subpattern recursion. + +The special item that consists of (? followed by a number greater than zero and +a closing parenthesis is a recursive call of the subpattern of the given +number, provided that it occurs inside that subpattern. (If not, it is a +"subroutine" call, which is described in the next section.) The special item +(?R) is a recursive call of the entire regular expression. + +For example, this PCRE pattern solves the nested parentheses problem (assume +the PCRE_EXTENDED option is set so that white space is ignored): + + \\( ( (?>[^()]+) | (?R) )* \\) + +First it matches an opening parenthesis. Then it matches any number of +substrings which can either be a sequence of non-parentheses, or a recursive +match of the pattern itself (that is a correctly parenthesized substring). +Finally there is a closing parenthesis. + +If this were part of a larger pattern, you would not want to recurse the entire +pattern, so instead you could use this: + + ( \\( ( (?>[^()]+) | (?1) )* \\) ) + +We have put the pattern into parentheses, and caused the recursion to refer to +them instead of the whole pattern. In a larger pattern, keeping track of +parenthesis numbers can be tricky. It may be more convenient to use named +parentheses instead. For this, PCRE uses (?P>name), which is an extension to +the Python syntax that PCRE uses for named parentheses (Perl does not provide +named parentheses). We could rewrite the above example as follows: + + (?P<pn> \\( ( (?>[^()]+) | (?P>pn) )* \\) ) + +This particular example pattern contains nested unlimited repeats, and so the +use of atomic grouping for matching strings of non-parentheses is important +when applying the pattern to strings that do not match. For example, when this +pattern is applied to + + (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() + +it yields "no match" quickly. However, if atomic grouping is not used, +the match runs for a very long time indeed because there are so many different +ways the + and * repeats can carve up the subject, and all have to be tested +before failure can be reported. + +At the end of a match, the values set for any capturing subpatterns are those +from the outermost level of the recursion at which the subpattern value is set. +If you want to obtain intermediate values, a callout function can be used (see +below and the +.\" HREF +\fBpcrecallout\fR +.\" +documentation). If the pattern above is matched against + + (ab(cd)ef) + +the value for the capturing parentheses is "ef", which is the last value taken +on at the top level. If additional parentheses are added, giving + + \\( ( ( (?>[^()]+) | (?R) )* ) \\) + ^ ^ + ^ ^ + +the string they capture is "ab(cd)ef", the contents of the top level +parentheses. If there are more than 15 capturing parentheses in a pattern, PCRE +has to obtain extra memory to store data during a recursion, which it does by +using \fBpcre_malloc\fR, freeing it via \fBpcre_free\fR afterwards. If no +memory can be obtained, the match fails with the PCRE_ERROR_NOMEMORY error. + +Do not confuse the (?R) item with the condition (R), which tests for recursion. +Consider this pattern, which matches text in angle brackets, allowing for +arbitrary nesting. Only digits are allowed in nested brackets (that is, when +recursing), whereas any characters are permitted at the outer level. + + < (?: (?(R) \\d++ | [^<>]*+) | (?R)) * > + +In this pattern, (?(R) is the start of a conditional subpattern, with two +different alternatives for the recursive and non-recursive cases. The (?R) item +is the actual recursive call. + +.\" HTML <a name="subpatternsassubroutines"></a> +.SH SUBPATTERNS AS SUBROUTINES +.rs +.sp +If the syntax for a recursive subpattern reference (either by number or by +name) is used outside the parentheses to which it refers, it operates like a +subroutine in a programming language. An earlier example pointed out that the +pattern + + (sens|respons)e and \\1ibility + +matches "sense and sensibility" and "response and responsibility", but not +"sense and responsibility". If instead the pattern + + (sens|respons)e and (?1)ibility + +is used, it does match "sense and responsibility" as well as the other two +strings. Such references must, however, follow the subpattern to which they +refer. + +.SH CALLOUTS +.rs +.sp +Perl has a feature whereby using the sequence (?{...}) causes arbitrary Perl +code to be obeyed in the middle of matching a regular expression. This makes it +possible, amongst other things, to extract different substrings that match the +same pair of parentheses when there is a repetition. + +PCRE provides a similar feature, but of course it cannot obey arbitrary Perl +code. The feature is called "callout". The caller of PCRE provides an external +function by putting its entry point in the global variable \fIpcre_callout\fR. +By default, this variable contains NULL, which disables all calling out. + +Within a regular expression, (?C) indicates the points at which the external +function is to be called. If you want to identify different callout points, you +can put a number less than 256 after the letter C. The default value is zero. +For example, this pattern has two callout points: + + (?C1)\dabc(?C2)def + +During matching, when PCRE reaches a callout point (and \fIpcre_callout\fR is +set), the external function is called. It is provided with the number of the +callout, and, optionally, one item of data originally supplied by the caller of +\fBpcre_exec()\fR. The callout function may cause matching to backtrack, or to +fail altogether. A complete description of the interface to the callout +function is given in the +.\" HREF +\fBpcrecallout\fR +.\" +documentation. + +.in 0 +Last updated: 03 February 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcreperform.3 b/external-libs/pcre/doc/pcreperform.3 new file mode 100644 index 00000000..52a332fc --- /dev/null +++ b/external-libs/pcre/doc/pcreperform.3 @@ -0,0 +1,66 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH PCRE PERFORMANCE +.rs +.sp +Certain items that may appear in regular expression patterns are more efficient +than others. It is more efficient to use a character class like [aeiou] than a +set of alternatives such as (a|e|i|o|u). In general, the simplest construction +that provides the required behaviour is usually the most efficient. Jeffrey +Friedl's book contains a lot of discussion about optimizing regular expressions +for efficient performance. + +When a pattern begins with .* not in parentheses, or in parentheses that are +not the subject of a backreference, and the PCRE_DOTALL option is set, the +pattern is implicitly anchored by PCRE, since it can match only at the start of +a subject string. However, if PCRE_DOTALL is not set, PCRE cannot make this +optimization, because the . metacharacter does not then match a newline, and if +the subject string contains newlines, the pattern may match from the character +immediately following one of them instead of from the very start. For example, +the pattern + + .*second + +matches the subject "first\\nand second" (where \\n stands for a newline +character), with the match starting at the seventh character. In order to do +this, PCRE has to retry the match starting after every newline in the subject. + +If you are using such a pattern with subject strings that do not contain +newlines, the best performance is obtained by setting PCRE_DOTALL, or starting +the pattern with ^.* to indicate explicit anchoring. That saves PCRE from +having to scan along the subject looking for a newline to restart at. + +Beware of patterns that contain nested indefinite repeats. These can take a +long time to run when applied to a string that does not match. Consider the +pattern fragment + + (a+)* + +This can match "aaaa" in 33 different ways, and this number increases very +rapidly as the string gets longer. (The * repeat can match 0, 1, 2, 3, or 4 +times, and for each of those cases other than 0, the + repeats can match +different numbers of times.) When the remainder of the pattern is such that the +entire match is going to fail, PCRE has in principle to try every possible +variation, and this can take an extremely long time. + +An optimization catches some of the more simple cases such as + + (a+)*b + +where a literal character follows. Before embarking on the standard matching +procedure, PCRE checks that there is a "b" later in the subject string, and if +there is not, it fails the match immediately. However, when there is no +following literal this optimization cannot be used. You can see the difference +by comparing the behaviour of + + (a+)*\\d + +with the pattern above. The former gives a failure almost instantly when +applied to a whole line of "a" characters, whereas the latter takes an +appreciable time with strings longer than about 20 characters. + +.in 0 +Last updated: 03 February 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcreposix.3 b/external-libs/pcre/doc/pcreposix.3 new file mode 100644 index 00000000..5198630f --- /dev/null +++ b/external-libs/pcre/doc/pcreposix.3 @@ -0,0 +1,194 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions. +.SH SYNOPSIS OF POSIX API +.B #include <pcreposix.h> +.PP +.SM +.br +.B int regcomp(regex_t *\fIpreg\fR, const char *\fIpattern\fR, +.ti +5n +.B int \fIcflags\fR); +.PP +.br +.B int regexec(regex_t *\fIpreg\fR, const char *\fIstring\fR, +.ti +5n +.B size_t \fInmatch\fR, regmatch_t \fIpmatch\fR[], int \fIeflags\fR); +.PP +.br +.B size_t regerror(int \fIerrcode\fR, const regex_t *\fIpreg\fR, +.ti +5n +.B char *\fIerrbuf\fR, size_t \fIerrbuf_size\fR); +.PP +.br +.B void regfree(regex_t *\fIpreg\fR); + +.SH DESCRIPTION +.rs +.sp +This set of functions provides a POSIX-style API to the PCRE regular expression +package. See the +.\" HREF +\fBpcreapi\fR +.\" +documentation for a description of the native API, which contains additional +functionality. + +The functions described here are just wrapper functions that ultimately call +the PCRE native API. Their prototypes are defined in the \fBpcreposix.h\fR +header file, and on Unix systems the library itself is called +\fBpcreposix.a\fR, so can be accessed by adding \fB-lpcreposix\fR to the +command for linking an application which uses them. Because the POSIX functions +call the native ones, it is also necessary to add \fR-lpcre\fR. + +I have implemented only those option bits that can be reasonably mapped to PCRE +native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined +with the value zero. They have no effect, but since programs that are written +to the POSIX interface often use them, this makes it easier to slot in PCRE as +a replacement library. Other POSIX options are not even defined. + +When PCRE is called via these functions, it is only the API that is POSIX-like +in style. The syntax and semantics of the regular expressions themselves are +still those of Perl, subject to the setting of various PCRE options, as +described below. "POSIX-like in style" means that the API approximates to the +POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding +domains it is probably even less compatible. + +The header for these functions is supplied as \fBpcreposix.h\fR to avoid any +potential clash with other POSIX libraries. It can, of course, be renamed or +aliased as \fBregex.h\fR, which is the "correct" name. It provides two +structure types, \fIregex_t\fR for compiled internal forms, and +\fIregmatch_t\fR for returning captured substrings. It also defines some +constants whose names start with "REG_"; these are used for setting options and +identifying error codes. + +.SH COMPILING A PATTERN +.rs +.sp +The function \fBregcomp()\fR is called to compile a pattern into an +internal form. The pattern is a C string terminated by a binary zero, and +is passed in the argument \fIpattern\fR. The \fIpreg\fR argument is a pointer +to a regex_t structure which is used as a base for storing information about +the compiled expression. + +The argument \fIcflags\fR is either zero, or contains one or more of the bits +defined by the following macros: + + REG_ICASE + +The PCRE_CASELESS option is set when the expression is passed for compilation +to the native function. + + REG_NEWLINE + +The PCRE_MULTILINE option is set when the expression is passed for compilation +to the native function. Note that this does \fInot\fR mimic the defined POSIX +behaviour for REG_NEWLINE (see the following section). + +In the absence of these flags, no options are passed to the native function. +This means the the regex is compiled with PCRE default semantics. In +particular, the way it handles newline characters in the subject string is the +Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only +\fIsome\fR of the effects specified for REG_NEWLINE. It does not affect the way +newlines are matched by . (they aren't) or by a negative class such as [^a] +(they are). + +The yield of \fBregcomp()\fR is zero on success, and non-zero otherwise. The +\fIpreg\fR structure is filled in on success, and one member of the structure +is public: \fIre_nsub\fR contains the number of capturing subpatterns in +the regular expression. Various error codes are defined in the header file. + +.SH MATCHING NEWLINE CHARACTERS +.rs +.sp +This area is not simple, because POSIX and Perl take different views of things. +It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never +intended to be a POSIX engine. The following table lists the different +possibilities for matching newline characters in PCRE: + + Default Change with + + . matches newline no PCRE_DOTALL + newline matches [^a] yes not changeable + $ matches \\n at end yes PCRE_DOLLARENDONLY + $ matches \\n in middle no PCRE_MULTILINE + ^ matches \\n in middle no PCRE_MULTILINE + +This is the equivalent table for POSIX: + + Default Change with + + . matches newline yes REG_NEWLINE + newline matches [^a] yes REG_NEWLINE + $ matches \\n at end no REG_NEWLINE + $ matches \\n in middle no REG_NEWLINE + ^ matches \\n in middle no REG_NEWLINE + +PCRE's behaviour is the same as Perl's, except that there is no equivalent for +PCRE_DOLLARENDONLY in Perl. In both PCRE and Perl, there is no way to stop +newline from matching [^a]. + +The default POSIX newline handling can be obtained by setting PCRE_DOTALL and +PCRE_DOLLARENDONLY, but there is no way to make PCRE behave exactly as for the +REG_NEWLINE action. + +.SH MATCHING A PATTERN +.rs +.sp +The function \fBregexec()\fR is called to match a pre-compiled pattern +\fIpreg\fR against a given \fIstring\fR, which is terminated by a zero byte, +subject to the options in \fIeflags\fR. These can be: + + REG_NOTBOL + +The PCRE_NOTBOL option is set when calling the underlying PCRE matching +function. + + REG_NOTEOL + +The PCRE_NOTEOL option is set when calling the underlying PCRE matching +function. + +The portion of the string that was matched, and also any captured substrings, +are returned via the \fIpmatch\fR argument, which points to an array of +\fInmatch\fR structures of type \fIregmatch_t\fR, containing the members +\fIrm_so\fR and \fIrm_eo\fR. These contain the offset to the first character of +each substring and the offset to the first character after the end of each +substring, respectively. The 0th element of the vector relates to the entire +portion of \fIstring\fR that was matched; subsequent elements relate to the +capturing subpatterns of the regular expression. Unused entries in the array +have both structure members set to -1. + +A successful match yields a zero return; various error codes are defined in the +header file, of which REG_NOMATCH is the "expected" failure code. + +.SH ERROR MESSAGES +.rs +.sp +The \fBregerror()\fR function maps a non-zero errorcode from either +\fBregcomp()\fR or \fBregexec()\fR to a printable message. If \fIpreg\fR is not +NULL, the error should have arisen from the use of that structure. A message +terminated by a binary zero is placed in \fIerrbuf\fR. The length of the +message, including the zero, is limited to \fIerrbuf_size\fR. The yield of the +function is the size of buffer needed to hold the whole message. + +.SH STORAGE +.rs +.sp +Compiling a regular expression causes memory to be allocated and associated +with the \fIpreg\fR structure. The function \fBregfree()\fR frees all such +memory, after which \fIpreg\fR may no longer be used as a compiled expression. + +.SH AUTHOR +.rs +.sp +Philip Hazel <ph10@cam.ac.uk> +.br +University Computing Service, +.br +Cambridge CB2 3QG, England. + +.in 0 +Last updated: 03 February 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcresample.3 b/external-libs/pcre/doc/pcresample.3 new file mode 100644 index 00000000..02a7a548 --- /dev/null +++ b/external-libs/pcre/doc/pcresample.3 @@ -0,0 +1,52 @@ +.TH PCRE 3 +.SH NAME +PCRE - Perl-compatible regular expressions +.SH PCRE SAMPLE PROGRAM +.rs +.sp +A simple, complete demonstration program, to get you started with using PCRE, +is supplied in the file \fIpcredemo.c\fR in the PCRE distribution. + +The program compiles the regular expression that is its first argument, and +matches it against the subject string in its second argument. No PCRE options +are set, and default character tables are used. If matching succeeds, the +program outputs the portion of the subject that matched, together with the +contents of any captured substrings. + +If the -g option is given on the command line, the program then goes on to +check for further matches of the same regular expression in the same subject +string. The logic is a little bit tricky because of the possibility of matching +an empty string. Comments in the code explain what is going on. + +On a Unix system that has PCRE installed in \fI/usr/local\fR, you can compile +the demonstration program using a command like this: + + gcc -o pcredemo pcredemo.c -I/usr/local/include \\ + -L/usr/local/lib -lpcre + +Then you can run simple tests like this: + + ./pcredemo 'cat|dog' 'the cat sat on the mat' + ./pcredemo -g 'cat|dog' 'the dog sat on the cat' + +Note that there is a much more comprehensive test program, called +\fBpcretest\fR, which supports many more facilities for testing regular +expressions and the PCRE library. The \fBpcredemo\fR program is provided as a +simple coding example. + +On some operating systems (e.g. Solaris) you may get an error like this when +you try to run \fBpcredemo\fR: + + ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory + +This is caused by the way shared library support works on those systems. You +need to add + + -R/usr/local/lib + +to the compile command to get round this problem. + +.in 0 +Last updated: 28 January 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcretest.1 b/external-libs/pcre/doc/pcretest.1 new file mode 100644 index 00000000..f3d69c83 --- /dev/null +++ b/external-libs/pcre/doc/pcretest.1 @@ -0,0 +1,364 @@ +.TH PCRETEST 1 +.SH NAME +pcretest - a program for testing Perl-compatible regular expressions. +.SH SYNOPSIS +.B pcretest "[-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]" + +\fBpcretest\fR was written as a test program for the PCRE regular expression +library itself, but it can also be used for experimenting with regular +expressions. This document describes the features of the test program; for +details of the regular expressions themselves, see the +.\" HREF +\fBpcrepattern\fR +.\" +documentation. For details of PCRE and its options, see the +.\" HREF +\fBpcreapi\fR +.\" +documentation. + +.SH OPTIONS +.rs +.sp +.TP 10 +\fB-C\fR +Output the version number of the PCRE library, and all available information +about the optional features that are included, and then exit. +.TP 10 +\fB-d\fR +Behave as if each regex had the \fB/D\fR modifier (see below); the internal +form is output after compilation. +.TP 10 +\fB-i\fR +Behave as if each regex had the \fB/I\fR modifier; information about the +compiled pattern is given after compilation. +.TP 10 +\fB-m\fR +Output the size of each compiled pattern after it has been compiled. This is +equivalent to adding /M to each regular expression. For compatibility with +earlier versions of pcretest, \fB-s\fR is a synonym for \fB-m\fR. +.TP 10 +\fB-o\fR \fIosize\fR +Set the number of elements in the output vector that is used when calling PCRE +to be \fIosize\fR. The default value is 45, which is enough for 14 capturing +subexpressions. The vector size can be changed for individual matching calls by +including \\O in the data line (see below). +.TP 10 +\fB-p\fR +Behave as if each regex has \fB/P\fR modifier; the POSIX wrapper API is used +to call PCRE. None of the other options has any effect when \fB-p\fR is set. +.TP 10 +\fB-t\fR +Run each compile, study, and match many times with a timer, and output +resulting time per compile or match (in milliseconds). Do not set \fB-t\fR with +\fB-m\fR, because you will then get the size output 20000 times and the timing +will be distorted. + +.SH DESCRIPTION +.rs +.sp +If \fBpcretest\fR is given two filename arguments, it reads from the first and +writes to the second. If it is given only one filename argument, it reads from +that file and writes to stdout. Otherwise, it reads from stdin and writes to +stdout, and prompts for each line of input, using "re>" to prompt for regular +expressions, and "data>" to prompt for data lines. + +The program handles any number of sets of input on a single input file. Each +set starts with a regular expression, and continues with any number of data +lines to be matched against the pattern. + +Each line is matched separately and independently. If you want to do +multiple-line matches, you have to use the \\n escape sequence in a single line +of input to encode the newline characters. The maximum length of data line is +30,000 characters. + +An empty line signals the end of the data lines, at which point a new regular +expression is read. The regular expressions are given enclosed in any +non-alphameric delimiters other than backslash, for example + + /(a|bc)x+yz/ + +White space before the initial delimiter is ignored. A regular expression may +be continued over several input lines, in which case the newline characters are +included within it. It is possible to include the delimiter within the pattern +by escaping it, for example + + /abc\\/def/ + +If you do so, the escape and the delimiter form part of the pattern, but since +delimiters are always non-alphameric, this does not affect its interpretation. +If the terminating delimiter is immediately followed by a backslash, for +example, + + /abc/\\ + +then a backslash is added to the end of the pattern. This is done to provide a +way of testing the error condition that arises if a pattern finishes with a +backslash, because + + /abc\\/ + +is interpreted as the first line of a pattern that starts with "abc/", causing +pcretest to read the next line as a continuation of the regular expression. + +.SH PATTERN MODIFIERS +.rs +.sp +The pattern may be followed by \fBi\fR, \fBm\fR, \fBs\fR, or \fBx\fR to set the +PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, +respectively. For example: + + /caseless/i + +These modifier letters have the same effect as they do in Perl. There are +others that set PCRE options that do not correspond to anything in Perl: +\fB/A\fR, \fB/E\fR, \fB/N\fR, \fB/U\fR, and \fB/X\fR set PCRE_ANCHORED, +PCRE_DOLLAR_ENDONLY, PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, and PCRE_EXTRA +respectively. + +Searching for all possible matches within each subject string can be requested +by the \fB/g\fR or \fB/G\fR modifier. After finding a match, PCRE is called +again to search the remainder of the subject string. The difference between +\fB/g\fR and \fB/G\fR is that the former uses the \fIstartoffset\fR argument to +\fBpcre_exec()\fR to start searching at a new point within the entire string +(which is in effect what Perl does), whereas the latter passes over a shortened +substring. This makes a difference to the matching process if the pattern +begins with a lookbehind assertion (including \\b or \\B). + +If any call to \fBpcre_exec()\fR in a \fB/g\fR or \fB/G\fR sequence matches an +empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED +flags set in order to search for another, non-empty, match at the same point. +If this second match fails, the start offset is advanced by one, and the normal +match is retried. This imitates the way Perl handles such cases when using the +\fB/g\fR modifier or the \fBsplit()\fR function. + +There are a number of other modifiers for controlling the way \fBpcretest\fR +operates. + +The \fB/+\fR modifier requests that as well as outputting the substring that +matched the entire pattern, pcretest should in addition output the remainder of +the subject string. This is useful for tests where the subject contains +multiple copies of the same substring. + +The \fB/L\fR modifier must be followed directly by the name of a locale, for +example, + + /pattern/Lfr + +For this reason, it must be the last modifier letter. The given locale is set, +\fBpcre_maketables()\fR is called to build a set of character tables for the +locale, and this is then passed to \fBpcre_compile()\fR when compiling the +regular expression. Without an \fB/L\fR modifier, NULL is passed as the tables +pointer; that is, \fB/L\fR applies only to the expression on which it appears. + +The \fB/I\fR modifier requests that \fBpcretest\fR output information about the +compiled expression (whether it is anchored, has a fixed first character, and +so on). It does this by calling \fBpcre_fullinfo()\fR after compiling an +expression, and outputting the information it gets back. If the pattern is +studied, the results of that are also output. + +The \fB/D\fR modifier is a PCRE debugging feature, which also assumes \fB/I\fR. +It causes the internal form of compiled regular expressions to be output after +compilation. If the pattern was studied, the information returned is also +output. + +The \fB/S\fR modifier causes \fBpcre_study()\fR to be called after the +expression has been compiled, and the results used when the expression is +matched. + +The \fB/M\fR modifier causes the size of memory block used to hold the compiled +pattern to be output. + +The \fB/P\fR modifier causes \fBpcretest\fR to call PCRE via the POSIX wrapper +API rather than its native API. When this is done, all other modifiers except +\fB/i\fR, \fB/m\fR, and \fB/+\fR are ignored. REG_ICASE is set if \fB/i\fR is +present, and REG_NEWLINE is set if \fB/m\fR is present. The wrapper functions +force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set. + +The \fB/8\fR modifier causes \fBpcretest\fR to call PCRE with the PCRE_UTF8 +option set. This turns on support for UTF-8 character handling in PCRE, +provided that it was compiled with this support enabled. This modifier also +causes any non-printing characters in output strings to be printed using the +\\x{hh...} notation if they are valid UTF-8 sequences. + +If the \fB/?\fR modifier is used with \fB/8\fR, it causes \fBpcretest\fR to +call \fBpcre_compile()\fR with the PCRE_NO_UTF8_CHECK option, to suppress the +checking of the string for UTF-8 validity. + +.SH CALLOUTS +.rs +.sp +If the pattern contains any callout requests, \fBpcretest\fR's callout function +will be called. By default, it displays the callout number, and the start and +current positions in the text at the callout time. For example, the output + + --->pqrabcdef + 0 ^ ^ + +indicates that callout number 0 occurred for a match attempt starting at the +fourth character of the subject string, when the pointer was at the seventh +character. The callout function returns zero (carry on matching) by default. + +Inserting callouts may be helpful when using \fBpcretest\fR to check +complicated regular expressions. For further information about callouts, see +the +.\" HREF +\fBpcrecallout\fR +.\" +documentation. + +For testing the PCRE library, additional control of callout behaviour is +available via escape sequences in the data, as described in the following +section. In particular, it is possible to pass in a number as callout data (the +default is zero). If the callout function receives a non-zero number, it +returns that value instead of zero. + +.SH DATA LINES +.rs +.sp +Before each data line is passed to \fBpcre_exec()\fR, leading and trailing +whitespace is removed, and it is then scanned for \\ escapes. Some of these are +pretty esoteric features, intended for checking out some of the more +complicated features of PCRE. If you are just testing "ordinary" regular +expressions, you probably don't need any of these. The following escapes are +recognized: + + \\a alarm (= BEL) + \\b backspace + \\e escape + \\f formfeed + \\n newline + \\r carriage return + \\t tab + \\v vertical tab + \\nnn octal character (up to 3 octal digits) + \\xhh hexadecimal character (up to 2 hex digits) + \\x{hh...} hexadecimal character, any number of digits + in UTF-8 mode + \\A pass the PCRE_ANCHORED option to \fBpcre_exec()\fR + \\B pass the PCRE_NOTBOL option to \fBpcre_exec()\fR + \\Cdd call pcre_copy_substring() for substring dd + after a successful match (any decimal number + less than 32) + \\Cname call pcre_copy_named_substring() for substring + "name" after a successful match (name termin- + ated by next non alphanumeric character) + \\C+ show the current captured substrings at callout + time + \\C- do not supply a callout function + \\C!n return 1 instead of 0 when callout number n is + reached + \\C!n!m return 1 instead of 0 when callout number n is + reached for the nth time + \\C*n pass the number n (may be negative) as callout + data + \\Gdd call pcre_get_substring() for substring dd + after a successful match (any decimal number + less than 32) + \\Gname call pcre_get_named_substring() for substring + "name" after a successful match (name termin- + ated by next non-alphanumeric character) + \\L call pcre_get_substringlist() after a + successful match + \\M discover the minimum MATCH_LIMIT setting + \\N pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fR + \\Odd set the size of the output vector passed to + \fBpcre_exec()\fR to dd (any number of decimal + digits) + \\S output details of memory get/free calls during matching + \\Z pass the PCRE_NOTEOL option to \fBpcre_exec()\fR + \\? pass the PCRE_NO_UTF8_CHECK option to + \fBpcre_exec()\fR + +If \\M is present, \fBpcretest\fR calls \fBpcre_exec()\fR several times, with +different values in the \fImatch_limit\fR field of the \fBpcre_extra\fR data +structure, until it finds the minimum number that is needed for +\fBpcre_exec()\fR to complete. This number is a measure of the amount of +recursion and backtracking that takes place, and checking it out can be +instructive. For most simple matches, the number is quite small, but for +patterns with very large numbers of matching possibilities, it can become large +very quickly with increasing length of subject string. + +When \\O is used, it may be higher or lower than the size set by the \fB-O\fR +option (or defaulted to 45); \\O applies only to the call of \fBpcre_exec()\fR +for the line in which it appears. + +A backslash followed by anything else just escapes the anything else. If the +very last character is a backslash, it is ignored. This gives a way of passing +an empty line as data, since a real empty line terminates the data input. + +If \fB/P\fR was present on the regex, causing the POSIX wrapper API to be used, +only \fB\B\fR, and \fB\Z\fR have any effect, causing REG_NOTBOL and REG_NOTEOL +to be passed to \fBregexec()\fR respectively. + +The use of \\x{hh...} to represent UTF-8 characters is not dependent on the use +of the \fB/8\fR modifier on the pattern. It is recognized always. There may be +any number of hexadecimal digits inside the braces. The result is from one to +six bytes, encoded according to the UTF-8 rules. + +.SH OUTPUT FROM PCRETEST +.rs +.sp +When a match succeeds, pcretest outputs the list of captured substrings that +\fBpcre_exec()\fR returns, starting with number 0 for the string that matched +the whole pattern. Here is an example of an interactive pcretest run. + + $ pcretest + PCRE version 4.00 08-Jan-2003 + + re> /^abc(\\d+)/ + data> abc123 + 0: abc123 + 1: 123 + data> xyz + No match + +If the strings contain any non-printing characters, they are output as \\0x +escapes, or as \\x{...} escapes if the \fB/8\fR modifier was present on the +pattern. If the pattern has the \fB/+\fR modifier, then the output for +substring 0 is followed by the the rest of the subject string, identified by +"0+" like this: + + re> /cat/+ + data> cataract + 0: cat + 0+ aract + +If the pattern has the \fB/g\fR or \fB/G\fR modifier, the results of successive +matching attempts are output in sequence, like this: + + re> /\\Bi(\\w\\w)/g + data> Mississippi + 0: iss + 1: ss + 0: iss + 1: ss + 0: ipp + 1: pp + +"No match" is output only if the first match attempt fails. + +If any of the sequences \fB\\C\fR, \fB\\G\fR, or \fB\\L\fR are present in a +data line that is successfully matched, the substrings extracted by the +convenience functions are output with C, G, or L after the string number +instead of a colon. This is in addition to the normal full list. The string +length (that is, the return from the extraction function) is given in +parentheses after each string for \fB\\C\fR and \fB\\G\fR. + +Note that while patterns can be continued over several lines (a plain ">" +prompt is used for continuations), data lines may not. However newlines can be +included in data by means of the \\n escape. + +.SH AUTHOR +.rs +.sp +Philip Hazel <ph10@cam.ac.uk> +.br +University Computing Service, +.br +Cambridge CB2 3QG, England. + +.in 0 +Last updated: 09 December 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/pcretest.txt b/external-libs/pcre/doc/pcretest.txt new file mode 100644 index 00000000..0e9cd138 --- /dev/null +++ b/external-libs/pcre/doc/pcretest.txt @@ -0,0 +1,357 @@ +PCRETEST(1) PCRETEST(1) + + + +NAME + pcretest - a program for testing Perl-compatible regular expressions. + +SYNOPSIS + pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination] + + pcretest was written as a test program for the PCRE regular expression + library itself, but it can also be used for experimenting with regular + expressions. This document describes the features of the test program; + for details of the regular expressions themselves, see the pcrepattern + documentation. For details of PCRE and its options, see the pcreapi + documentation. + + +OPTIONS + + + -C Output the version number of the PCRE library, and all avail- + able information about the optional features that are + included, and then exit. + + -d Behave as if each regex had the /D modifier (see below); the + internal form is output after compilation. + + -i Behave as if each regex had the /I modifier; information + about the compiled pattern is given after compilation. + + -m Output the size of each compiled pattern after it has been + compiled. This is equivalent to adding /M to each regular + expression. For compatibility with earlier versions of + pcretest, -s is a synonym for -m. + + -o osize Set the number of elements in the output vector that is used + when calling PCRE to be osize. The default value is 45, which + is enough for 14 capturing subexpressions. The vector size + can be changed for individual matching calls by including \O + in the data line (see below). + + -p Behave as if each regex has /P modifier; the POSIX wrapper + API is used to call PCRE. None of the other options has any + effect when -p is set. + + -t Run each compile, study, and match many times with a timer, + and output resulting time per compile or match (in millisec- + onds). Do not set -t with -m, because you will then get the + size output 20000 times and the timing will be distorted. + + +DESCRIPTION + + If pcretest is given two filename arguments, it reads from the first + and writes to the second. If it is given only one filename argument, it + reads from that file and writes to stdout. Otherwise, it reads from + stdin and writes to stdout, and prompts for each line of input, using + "re>" to prompt for regular expressions, and "data>" to prompt for data + lines. + + The program handles any number of sets of input on a single input file. + Each set starts with a regular expression, and continues with any num- + ber of data lines to be matched against the pattern. + + Each line is matched separately and independently. If you want to do + multiple-line matches, you have to use the \n escape sequence in a sin- + gle line of input to encode the newline characters. The maximum length + of data line is 30,000 characters. + + An empty line signals the end of the data lines, at which point a new + regular expression is read. The regular expressions are given enclosed + in any non-alphameric delimiters other than backslash, for example + + /(a|bc)x+yz/ + + White space before the initial delimiter is ignored. A regular expres- + sion may be continued over several input lines, in which case the new- + line characters are included within it. It is possible to include the + delimiter within the pattern by escaping it, for example + + /abc\/def/ + + If you do so, the escape and the delimiter form part of the pattern, + but since delimiters are always non-alphameric, this does not affect + its interpretation. If the terminating delimiter is immediately fol- + lowed by a backslash, for example, + + /abc/\ + + then a backslash is added to the end of the pattern. This is done to + provide a way of testing the error condition that arises if a pattern + finishes with a backslash, because + + /abc\/ + + is interpreted as the first line of a pattern that starts with "abc/", + causing pcretest to read the next line as a continuation of the regular + expression. + + +PATTERN MODIFIERS + + The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS, + PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. + For example: + + /caseless/i + + These modifier letters have the same effect as they do in Perl. There + are others that set PCRE options that do not correspond to anything in + Perl: /A, /E, /N, /U, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, + PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, and PCRE_EXTRA respectively. + + Searching for all possible matches within each subject string can be + requested by the /g or /G modifier. After finding a match, PCRE is + called again to search the remainder of the subject string. The differ- + ence between /g and /G is that the former uses the startoffset argument + to pcre_exec() to start searching at a new point within the entire + string (which is in effect what Perl does), whereas the latter passes + over a shortened substring. This makes a difference to the matching + process if the pattern begins with a lookbehind assertion (including \b + or \B). + + If any call to pcre_exec() in a /g or /G sequence matches an empty + string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED + flags set in order to search for another, non-empty, match at the same + point. If this second match fails, the start offset is advanced by + one, and the normal match is retried. This imitates the way Perl han- + dles such cases when using the /g modifier or the split() function. + + There are a number of other modifiers for controlling the way pcretest + operates. + + The /+ modifier requests that as well as outputting the substring that + matched the entire pattern, pcretest should in addition output the + remainder of the subject string. This is useful for tests where the + subject contains multiple copies of the same substring. + + The /L modifier must be followed directly by the name of a locale, for + example, + + /pattern/Lfr + + For this reason, it must be the last modifier letter. The given locale + is set, pcre_maketables() is called to build a set of character tables + for the locale, and this is then passed to pcre_compile() when compil- + ing the regular expression. Without an /L modifier, NULL is passed as + the tables pointer; that is, /L applies only to the expression on which + it appears. + + The /I modifier requests that pcretest output information about the + compiled expression (whether it is anchored, has a fixed first charac- + ter, and so on). It does this by calling pcre_fullinfo() after compil- + ing an expression, and outputting the information it gets back. If the + pattern is studied, the results of that are also output. + + The /D modifier is a PCRE debugging feature, which also assumes /I. It + causes the internal form of compiled regular expressions to be output + after compilation. If the pattern was studied, the information returned + is also output. + + The /S modifier causes pcre_study() to be called after the expression + has been compiled, and the results used when the expression is matched. + + The /M modifier causes the size of memory block used to hold the com- + piled pattern to be output. + + The /P modifier causes pcretest to call PCRE via the POSIX wrapper API + rather than its native API. When this is done, all other modifiers + except /i, /m, and /+ are ignored. REG_ICASE is set if /i is present, + and REG_NEWLINE is set if /m is present. The wrapper functions force + PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set. + + The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option + set. This turns on support for UTF-8 character handling in PCRE, pro- + vided that it was compiled with this support enabled. This modifier + also causes any non-printing characters in output strings to be printed + using the \x{hh...} notation if they are valid UTF-8 sequences. + + If the /? modifier is used with /8, it causes pcretest to call + pcre_compile() with the PCRE_NO_UTF8_CHECK option, to suppress the + checking of the string for UTF-8 validity. + + +CALLOUTS + + If the pattern contains any callout requests, pcretest's callout func- + tion will be called. By default, it displays the callout number, and + the start and current positions in the text at the callout time. For + example, the output + + --->pqrabcdef + 0 ^ ^ + + indicates that callout number 0 occurred for a match attempt starting + at the fourth character of the subject string, when the pointer was at + the seventh character. The callout function returns zero (carry on + matching) by default. + + Inserting callouts may be helpful when using pcretest to check compli- + cated regular expressions. For further information about callouts, see + the pcrecallout documentation. + + For testing the PCRE library, additional control of callout behaviour + is available via escape sequences in the data, as described in the fol- + lowing section. In particular, it is possible to pass in a number as + callout data (the default is zero). If the callout function receives a + non-zero number, it returns that value instead of zero. + + +DATA LINES + + Before each data line is passed to pcre_exec(), leading and trailing + whitespace is removed, and it is then scanned for \ escapes. Some of + these are pretty esoteric features, intended for checking out some of + the more complicated features of PCRE. If you are just testing "ordi- + nary" regular expressions, you probably don't need any of these. The + following escapes are recognized: + + \a alarm (= BEL) + \b backspace + \e escape + \f formfeed + \n newline + \r carriage return + \t tab + \v vertical tab + \nnn octal character (up to 3 octal digits) + \xhh hexadecimal character (up to 2 hex digits) + \x{hh...} hexadecimal character, any number of digits + in UTF-8 mode + \A pass the PCRE_ANCHORED option to pcre_exec() + \B pass the PCRE_NOTBOL option to pcre_exec() + \Cdd call pcre_copy_substring() for substring dd + after a successful match (any decimal number + less than 32) + \Cname call pcre_copy_named_substring() for substring + "name" after a successful match (name termin- + ated by next non alphanumeric character) + \C+ show the current captured substrings at callout + time + \C- do not supply a callout function + \C!n return 1 instead of 0 when callout number n is + reached + \C!n!m return 1 instead of 0 when callout number n is + reached for the nth time + \C*n pass the number n (may be negative) as callout + data + \Gdd call pcre_get_substring() for substring dd + after a successful match (any decimal number + less than 32) + \Gname call pcre_get_named_substring() for substring + "name" after a successful match (name termin- + ated by next non-alphanumeric character) + \L call pcre_get_substringlist() after a + successful match + \M discover the minimum MATCH_LIMIT setting + \N pass the PCRE_NOTEMPTY option to pcre_exec() + \Odd set the size of the output vector passed to + pcre_exec() to dd (any number of decimal + digits) + \S output details of memory get/free calls during matching + \Z pass the PCRE_NOTEOL option to pcre_exec() + \? pass the PCRE_NO_UTF8_CHECK option to + pcre_exec() + + If \M is present, pcretest calls pcre_exec() several times, with dif- + ferent values in the match_limit field of the pcre_extra data struc- + ture, until it finds the minimum number that is needed for pcre_exec() + to complete. This number is a measure of the amount of recursion and + backtracking that takes place, and checking it out can be instructive. + For most simple matches, the number is quite small, but for patterns + with very large numbers of matching possibilities, it can become large + very quickly with increasing length of subject string. + + When \O is used, it may be higher or lower than the size set by the -O + option (or defaulted to 45); \O applies only to the call of pcre_exec() + for the line in which it appears. + + A backslash followed by anything else just escapes the anything else. + If the very last character is a backslash, it is ignored. This gives a + way of passing an empty line as data, since a real empty line termi- + nates the data input. + + If /P was present on the regex, causing the POSIX wrapper API to be + used, only 0 causing REG_NOTBOL and REG_NOTEOL to be passed to + regexec() respectively. + + The use of \x{hh...} to represent UTF-8 characters is not dependent on + the use of the /8 modifier on the pattern. It is recognized always. + There may be any number of hexadecimal digits inside the braces. The + result is from one to six bytes, encoded according to the UTF-8 rules. + + +OUTPUT FROM PCRETEST + + When a match succeeds, pcretest outputs the list of captured substrings + that pcre_exec() returns, starting with number 0 for the string that + matched the whole pattern. Here is an example of an interactive + pcretest run. + + $ pcretest + PCRE version 4.00 08-Jan-2003 + + re> /^abc(\d+)/ + data> abc123 + 0: abc123 + 1: 123 + data> xyz + No match + + If the strings contain any non-printing characters, they are output as + \0x escapes, or as \x{...} escapes if the /8 modifier was present on + the pattern. If the pattern has the /+ modifier, then the output for + substring 0 is followed by the the rest of the subject string, identi- + fied by "0+" like this: + + re> /cat/+ + data> cataract + 0: cat + 0+ aract + + If the pattern has the /g or /G modifier, the results of successive + matching attempts are output in sequence, like this: + + re> /\Bi(\w\w)/g + data> Mississippi + 0: iss + 1: ss + 0: iss + 1: ss + 0: ipp + 1: pp + + "No match" is output only if the first match attempt fails. + + If any of the sequences \C, \G, or \L are present in a data line that + is successfully matched, the substrings extracted by the convenience + functions are output with C, G, or L after the string number instead of + a colon. This is in addition to the normal full list. The string length + (that is, the return from the extraction function) is given in paren- + theses after each string for \C and \G. + + Note that while patterns can be continued over several lines (a plain + ">" prompt is used for continuations), data lines may not. However new- + lines can be included in data by means of the \n escape. + + +AUTHOR + + Philip Hazel <ph10@cam.ac.uk> + University Computing Service, + Cambridge CB2 3QG, England. + +Last updated: 09 December 2003 +Copyright (c) 1997-2003 University of Cambridge. diff --git a/external-libs/pcre/doc/perltest.txt b/external-libs/pcre/doc/perltest.txt new file mode 100644 index 00000000..9ea9d932 --- /dev/null +++ b/external-libs/pcre/doc/perltest.txt @@ -0,0 +1,34 @@ +The perltest program +-------------------- + +The perltest program tests Perl's regular expressions; it has the same +specification as pcretest, and so can be given identical input, except that +input patterns can be followed only by Perl's lower case modifiers and /+ (as +used by pcretest), which is recognized and handled by the program. + +The data lines are processed as Perl double-quoted strings, so if they contain +" \ $ or @ characters, these have to be escaped. For this reason, all such +characters in testinput1 and testinput3 are escaped so that they can be used +for perltest as well as for pcretest, and the special upper case modifiers such +as /A that pcretest recognizes are not used in these files. The output should +be identical, apart from the initial identifying banner. + +The perltest script can also test UTF-8 features. It works as is for Perl 5.8 +or higher. It recognizes the special modifier /8 that pcretest uses to invoke +UTF-8 functionality. The testinput5 file can be fed to perltest to run UTF-8 +tests. + +For Perl 5.6, perltest won't work unmodified for the UTF-8 tests. You need to +uncomment the "use utf8" lines that it contains. It is best to do this on a +copy of the script, because for non-UTF-8 tests, these lines should remain +commented out. + +The testinput2 and testinput4 files are not suitable for feeding to perltest, +since they do make use of the special upper case modifiers and escapes that +pcretest uses to test some features of PCRE. The first of these files also +contains malformed regular expressions, in order to check that PCRE diagnoses +them correctly. Similarly, testinput6 tests UTF-8 features that do not relate +to Perl. + +Philip Hazel <ph10@cam.ac.uk> +August 2002 |