1<html> 2<head> 3<title>pcreposix specification</title> 4</head> 5<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6<h1>pcreposix man page</h1> 7<p> 8Return to the <a href="index.html">PCRE index page</a>. 9</p> 10<p> 11This page is part of the PCRE HTML documentation. It was generated automatically 12from the original man page. If there is any nonsense in it, please consult the 13man page, in case the conversion went wrong. 14<br> 15<ul> 16<li><a name="TOC1" href="#SEC1">SYNOPSIS OF POSIX API</a> 17<li><a name="TOC2" href="#SEC2">DESCRIPTION</a> 18<li><a name="TOC3" href="#SEC3">COMPILING A PATTERN</a> 19<li><a name="TOC4" href="#SEC4">MATCHING NEWLINE CHARACTERS</a> 20<li><a name="TOC5" href="#SEC5">MATCHING A PATTERN</a> 21<li><a name="TOC6" href="#SEC6">ERROR MESSAGES</a> 22<li><a name="TOC7" href="#SEC7">MEMORY USAGE</a> 23<li><a name="TOC8" href="#SEC8">AUTHOR</a> 24<li><a name="TOC9" href="#SEC9">REVISION</a> 25</ul> 26<br><a name="SEC1" href="#TOC1">SYNOPSIS OF POSIX API</a><br> 27<P> 28<b>#include <pcreposix.h></b> 29</P> 30<P> 31<b>int regcomp(regex_t *<i>preg</i>, const char *<i>pattern</i>,</b> 32<b>int <i>cflags</i>);</b> 33</P> 34<P> 35<b>int regexec(regex_t *<i>preg</i>, const char *<i>string</i>,</b> 36<b>size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b> 37</P> 38<P> 39<b>size_t regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b> 40<b>char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b> 41</P> 42<P> 43<b>void regfree(regex_t *<i>preg</i>);</b> 44</P> 45<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br> 46<P> 47This set of functions provides a POSIX-style API for the PCRE regular 48expression 8-bit library. See the 49<a href="pcreapi.html"><b>pcreapi</b></a> 50documentation for a description of PCRE's native API, which contains much 51additional functionality. There is no POSIX-style wrapper for PCRE's 16-bit 52library. 53</P> 54<P> 55The functions described here are just wrapper functions that ultimately call 56the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b> 57header file, and on Unix systems the library itself is called 58<b>pcreposix.a</b>, so can be accessed by adding <b>-lpcreposix</b> to the 59command for linking an application that uses them. Because the POSIX functions 60call the native ones, it is also necessary to add <b>-lpcre</b>. 61</P> 62<P> 63I have implemented only those POSIX option bits that can be reasonably mapped 64to PCRE native options. In addition, the option REG_EXTENDED is defined with 65the value zero. This has no effect, but since programs that are written to the 66POSIX interface often use it, this makes it easier to slot in PCRE as a 67replacement library. Other POSIX options are not even defined. 68</P> 69<P> 70There are also some other options that are not defined by POSIX. These have 71been added at the request of users who want to make use of certain 72PCRE-specific features via the POSIX calling interface. 73</P> 74<P> 75When PCRE is called via these functions, it is only the API that is POSIX-like 76in style. The syntax and semantics of the regular expressions themselves are 77still those of Perl, subject to the setting of various PCRE options, as 78described below. "POSIX-like in style" means that the API approximates to the 79POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding 80domains it is probably even less compatible. 81</P> 82<P> 83The header for these functions is supplied as <b>pcreposix.h</b> to avoid any 84potential clash with other POSIX libraries. It can, of course, be renamed or 85aliased as <b>regex.h</b>, which is the "correct" name. It provides two 86structure types, <i>regex_t</i> for compiled internal forms, and 87<i>regmatch_t</i> for returning captured substrings. It also defines some 88constants whose names start with "REG_"; these are used for setting options and 89identifying error codes. 90</P> 91<br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br> 92<P> 93The function <b>regcomp()</b> is called to compile a pattern into an 94internal form. The pattern is a C string terminated by a binary zero, and 95is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer 96to a <b>regex_t</b> structure that is used as a base for storing information 97about the compiled regular expression. 98</P> 99<P> 100The argument <i>cflags</i> is either zero, or contains one or more of the bits 101defined by the following macros: 102<pre> 103 REG_DOTALL 104</pre> 105The PCRE_DOTALL option is set when the regular expression is passed for 106compilation to the native function. Note that REG_DOTALL is not part of the 107POSIX standard. 108<pre> 109 REG_ICASE 110</pre> 111The PCRE_CASELESS option is set when the regular expression is passed for 112compilation to the native function. 113<pre> 114 REG_NEWLINE 115</pre> 116The PCRE_MULTILINE option is set when the regular expression is passed for 117compilation to the native function. Note that this does <i>not</i> mimic the 118defined POSIX behaviour for REG_NEWLINE (see the following section). 119<pre> 120 REG_NOSUB 121</pre> 122The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed 123for compilation to the native function. In addition, when a pattern that is 124compiled with this flag is passed to <b>regexec()</b> for matching, the 125<i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings 126are returned. 127<pre> 128 REG_UCP 129</pre> 130The PCRE_UCP option is set when the regular expression is passed for 131compilation to the native function. This causes PCRE to use Unicode properties 132when matchine \d, \w, etc., instead of just recognizing ASCII values. Note 133that REG_UTF8 is not part of the POSIX standard. 134<pre> 135 REG_UNGREEDY 136</pre> 137The PCRE_UNGREEDY option is set when the regular expression is passed for 138compilation to the native function. Note that REG_UNGREEDY is not part of the 139POSIX standard. 140<pre> 141 REG_UTF8 142</pre> 143The PCRE_UTF8 option is set when the regular expression is passed for 144compilation to the native function. This causes the pattern itself and all data 145strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8 146is not part of the POSIX standard. 147</P> 148<P> 149In the absence of these flags, no options are passed to the native function. 150This means the the regex is compiled with PCRE default semantics. In 151particular, the way it handles newline characters in the subject string is the 152Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only 153<i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way 154newlines are matched by . (they are not) or by a negative class such as [^a] 155(they are). 156</P> 157<P> 158The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The 159<i>preg</i> structure is filled in on success, and one member of the structure 160is public: <i>re_nsub</i> contains the number of capturing subpatterns in 161the regular expression. Various error codes are defined in the header file. 162</P> 163<P> 164NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to 165use the contents of the <i>preg</i> structure. If, for example, you pass it to 166<b>regexec()</b>, the result is undefined and your program is likely to crash. 167</P> 168<br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br> 169<P> 170This area is not simple, because POSIX and Perl take different views of things. 171It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never 172intended to be a POSIX engine. The following table lists the different 173possibilities for matching newline characters in PCRE: 174<pre> 175 Default Change with 176 177 . matches newline no PCRE_DOTALL 178 newline matches [^a] yes not changeable 179 $ matches \n at end yes PCRE_DOLLARENDONLY 180 $ matches \n in middle no PCRE_MULTILINE 181 ^ matches \n in middle no PCRE_MULTILINE 182</pre> 183This is the equivalent table for POSIX: 184<pre> 185 Default Change with 186 187 . matches newline yes REG_NEWLINE 188 newline matches [^a] yes REG_NEWLINE 189 $ matches \n at end no REG_NEWLINE 190 $ matches \n in middle no REG_NEWLINE 191 ^ matches \n in middle no REG_NEWLINE 192</pre> 193PCRE's behaviour is the same as Perl's, except that there is no equivalent for 194PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop 195newline from matching [^a]. 196</P> 197<P> 198The default POSIX newline handling can be obtained by setting PCRE_DOTALL and 199PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the 200REG_NEWLINE action. 201</P> 202<br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br> 203<P> 204The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i> 205against a given <i>string</i>, which is by default terminated by a zero byte 206(but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can 207be: 208<pre> 209 REG_NOTBOL 210</pre> 211The PCRE_NOTBOL option is set when calling the underlying PCRE matching 212function. 213<pre> 214 REG_NOTEMPTY 215</pre> 216The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching 217function. Note that REG_NOTEMPTY is not part of the POSIX standard. However, 218setting this option can give more POSIX-like behaviour in some situations. 219<pre> 220 REG_NOTEOL 221</pre> 222The PCRE_NOTEOL option is set when calling the underlying PCRE matching 223function. 224<pre> 225 REG_STARTEND 226</pre> 227The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and 228to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i> 229(there need not actually be a NUL at that location), regardless of the value of 230<i>nmatch</i>. This is a BSD extension, compatible with but not specified by 231IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software 232intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does 233not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not 234how it is matched. 235</P> 236<P> 237If the pattern was compiled with the REG_NOSUB flag, no data about any matched 238strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of 239<b>regexec()</b> are ignored. 240</P> 241<P> 242If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL, 243no data about any matched strings is returned. 244</P> 245<P> 246Otherwise,the portion of the string that was matched, and also any captured 247substrings, are returned via the <i>pmatch</i> argument, which points to an 248array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the 249members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first 250character of each substring and the offset to the first character after the end 251of each substring, respectively. The 0th element of the vector relates to the 252entire portion of <i>string</i> that was matched; subsequent elements relate to 253the capturing subpatterns of the regular expression. Unused entries in the 254array have both structure members set to -1. 255</P> 256<P> 257A successful match yields a zero return; various error codes are defined in the 258header file, of which REG_NOMATCH is the "expected" failure code. 259</P> 260<br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br> 261<P> 262The <b>regerror()</b> function maps a non-zero errorcode from either 263<b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not 264NULL, the error should have arisen from the use of that structure. A message 265terminated by a binary zero is placed in <i>errbuf</i>. The length of the 266message, including the zero, is limited to <i>errbuf_size</i>. The yield of the 267function is the size of buffer needed to hold the whole message. 268</P> 269<br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br> 270<P> 271Compiling a regular expression causes memory to be allocated and associated 272with the <i>preg</i> structure. The function <b>regfree()</b> frees all such 273memory, after which <i>preg</i> may no longer be used as a compiled expression. 274</P> 275<br><a name="SEC8" href="#TOC1">AUTHOR</a><br> 276<P> 277Philip Hazel 278<br> 279University Computing Service 280<br> 281Cambridge CB2 3QH, England. 282<br> 283</P> 284<br><a name="SEC9" href="#TOC1">REVISION</a><br> 285<P> 286Last updated: 09 January 2012 287<br> 288Copyright © 1997-2012 University of Cambridge. 289<br> 290<p> 291Return to the <a href="index.html">PCRE index page</a>. 292</p> 293