diff options
Diffstat (limited to 'doc/html/pcreposix.html')
| -rw-r--r-- | doc/html/pcreposix.html | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/doc/html/pcreposix.html b/doc/html/pcreposix.html new file mode 100644 index 0000000..18924cf --- /dev/null +++ b/doc/html/pcreposix.html @@ -0,0 +1,290 @@ +<html> +<head> +<title>pcreposix specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +<h1>pcreposix man page</h1> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> +<p> +This page is part of the PCRE HTML documentation. It was 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">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">MEMORY USAGE</a> +<li><a name="TOC8" href="#SEC8">AUTHOR</a> +<li><a name="TOC9" href="#SEC9">REVISION</a> +</ul> +<br><a name="SEC1" href="#TOC1">SYNOPSIS</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> +<br> +<br> +<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> +<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> +<br> +<br> +<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 for the PCRE regular +expression 8-bit library. See the +<a href="pcreapi.html"><b>pcreapi</b></a> +documentation for a description of PCRE's native API, which contains much +additional functionality. There is no POSIX-style wrapper for PCRE's 16-bit +and 32-bit library. +</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 that uses them. Because the POSIX functions +call the native ones, it is also necessary to add <b>-lpcre</b>. +</P> +<P> +I have implemented only those POSIX option bits that can be reasonably mapped +to PCRE native options. In addition, the option REG_EXTENDED is defined with +the value zero. This has no effect, but since programs that are written to the +POSIX interface often use it, this makes it easier to slot in PCRE as a +replacement library. Other POSIX options are not even defined. +</P> +<P> +There are also some other options that are not defined by POSIX. These have +been added at the request of users who want to make use of certain +PCRE-specific features via the POSIX calling interface. +</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 <b>regex_t</b> structure that is used as a base for storing information +about the compiled regular expression. +</P> +<P> +The argument <i>cflags</i> is either zero, or contains one or more of the bits +defined by the following macros: +<pre> + REG_DOTALL +</pre> +The PCRE_DOTALL option is set when the regular expression is passed for +compilation to the native function. Note that REG_DOTALL is not part of the +POSIX standard. +<pre> + REG_ICASE +</pre> +The PCRE_CASELESS option is set when the regular expression is passed for +compilation to the native function. +<pre> + REG_NEWLINE +</pre> +The PCRE_MULTILINE option is set when the regular 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). +<pre> + REG_NOSUB +</pre> +The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed +for compilation to the native function. In addition, when a pattern that is +compiled with this flag is passed to <b>regexec()</b> for matching, the +<i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings +are returned. +<pre> + REG_UCP +</pre> +The PCRE_UCP option is set when the regular expression is passed for +compilation to the native function. This causes PCRE to use Unicode properties +when matchine \d, \w, etc., instead of just recognizing ASCII values. Note +that REG_UTF8 is not part of the POSIX standard. +<pre> + REG_UNGREEDY +</pre> +The PCRE_UNGREEDY option is set when the regular expression is passed for +compilation to the native function. Note that REG_UNGREEDY is not part of the +POSIX standard. +<pre> + REG_UTF8 +</pre> +The PCRE_UTF8 option is set when the regular expression is passed for +compilation to the native function. This causes the pattern itself and all data +strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8 +is not part of the POSIX standard. +</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 are not) 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> +<P> +NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to +use the contents of the <i>preg</i> structure. If, for example, you pass it to +<b>regexec()</b>, the result is undefined and your program is likely to crash. +</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: +<pre> + 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 +</pre> +This is the equivalent table for POSIX: +<pre> + 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 +</pre> +PCRE's behaviour is the same as Perl's, except that there is no equivalent for +PCRE_DOLLAR_ENDONLY 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_DOLLAR_ENDONLY, 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 compiled pattern <i>preg</i> +against a given <i>string</i>, which is by default terminated by a zero byte +(but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can +be: +<pre> + REG_NOTBOL +</pre> +The PCRE_NOTBOL option is set when calling the underlying PCRE matching +function. +<pre> + REG_NOTEMPTY +</pre> +The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching +function. Note that REG_NOTEMPTY is not part of the POSIX standard. However, +setting this option can give more POSIX-like behaviour in some situations. +<pre> + REG_NOTEOL +</pre> +The PCRE_NOTEOL option is set when calling the underlying PCRE matching +function. +<pre> + REG_STARTEND +</pre> +The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and +to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i> +(there need not actually be a NUL at that location), regardless of the value of +<i>nmatch</i>. This is a BSD extension, compatible with but not specified by +IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software +intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does +not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not +how it is matched. +</P> +<P> +If the pattern was compiled with the REG_NOSUB flag, no data about any matched +strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of +<b>regexec()</b> are ignored. +</P> +<P> +If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL, +no data about any matched strings is returned. +</P> +<P> +Otherwise,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">MEMORY USAGE</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 +<br> +University Computing Service +<br> +Cambridge CB2 3QH, England. +<br> +</P> +<br><a name="SEC9" href="#TOC1">REVISION</a><br> +<P> +Last updated: 09 January 2012 +<br> +Copyright © 1997-2012 University of Cambridge. +<br> +<p> +Return to the <a href="index.html">PCRE index page</a>. +</p> |