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> 8 Return to the <a href="index.html">PCRE index page</a>. 9 </p> 10 <p> 11 This page is part of the PCRE HTML documentation. It was generated automatically 12 from the original man page. If there is any nonsense in it, please consult the 13 man 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> 47 This set of functions provides a POSIX-style API to the PCRE regular expression 48 package. See the 49 <a href="pcreapi.html"><b>pcreapi</b></a> 50 documentation for a description of PCRE's native API, which contains much 51 additional functionality. 52 </P> 53 <P> 54 The functions described here are just wrapper functions that ultimately call 55 the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b> 56 header file, and on Unix systems the library itself is called 57 <b>pcreposix.a</b>, so can be accessed by adding <b>-lpcreposix</b> to the 58 command for linking an application that uses them. Because the POSIX functions 59 call the native ones, it is also necessary to add <b>-lpcre</b>. 60 </P> 61 <P> 62 I have implemented only those POSIX option bits that can be reasonably mapped 63 to PCRE native options. In addition, the option REG_EXTENDED is defined with 64 the value zero. This has no effect, but since programs that are written to the 65 POSIX interface often use it, this makes it easier to slot in PCRE as a 66 replacement library. Other POSIX options are not even defined. 67 </P> 68 <P> 69 There are also some other options that are not defined by POSIX. These have 70 been added at the request of users who want to make use of certain 71 PCRE-specific features via the POSIX calling interface. 72 </P> 73 <P> 74 When PCRE is called via these functions, it is only the API that is POSIX-like 75 in style. The syntax and semantics of the regular expressions themselves are 76 still those of Perl, subject to the setting of various PCRE options, as 77 described below. "POSIX-like in style" means that the API approximates to the 78 POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding 79 domains it is probably even less compatible. 80 </P> 81 <P> 82 The header for these functions is supplied as <b>pcreposix.h</b> to avoid any 83 potential clash with other POSIX libraries. It can, of course, be renamed or 84 aliased as <b>regex.h</b>, which is the "correct" name. It provides two 85 structure types, <i>regex_t</i> for compiled internal forms, and 86 <i>regmatch_t</i> for returning captured substrings. It also defines some 87 constants whose names start with "REG_"; these are used for setting options and 88 identifying error codes. 89 </P> 90 <br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br> 91 <P> 92 The function <b>regcomp()</b> is called to compile a pattern into an 93 internal form. The pattern is a C string terminated by a binary zero, and 94 is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer 95 to a <b>regex_t</b> structure that is used as a base for storing information 96 about the compiled regular expression. 97 </P> 98 <P> 99 The argument <i>cflags</i> is either zero, or contains one or more of the bits 100 defined by the following macros: 101 <pre> 102 REG_DOTALL 103 </pre> 104 The PCRE_DOTALL option is set when the regular expression is passed for 105 compilation to the native function. Note that REG_DOTALL is not part of the 106 POSIX standard. 107 <pre> 108 REG_ICASE 109 </pre> 110 The PCRE_CASELESS option is set when the regular expression is passed for 111 compilation to the native function. 112 <pre> 113 REG_NEWLINE 114 </pre> 115 The PCRE_MULTILINE option is set when the regular expression is passed for 116 compilation to the native function. Note that this does <i>not</i> mimic the 117 defined POSIX behaviour for REG_NEWLINE (see the following section). 118 <pre> 119 REG_NOSUB 120 </pre> 121 The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed 122 for compilation to the native function. In addition, when a pattern that is 123 compiled with this flag is passed to <b>regexec()</b> for matching, the 124 <i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings 125 are returned. 126 <pre> 127 REG_UCP 128 </pre> 129 The PCRE_UCP option is set when the regular expression is passed for 130 compilation to the native function. This causes PCRE to use Unicode properties 131 when matchine \d, \w, etc., instead of just recognizing ASCII values. Note 132 that REG_UTF8 is not part of the POSIX standard. 133 <pre> 134 REG_UNGREEDY 135 </pre> 136 The PCRE_UNGREEDY option is set when the regular expression is passed for 137 compilation to the native function. Note that REG_UNGREEDY is not part of the 138 POSIX standard. 139 <pre> 140 REG_UTF8 141 </pre> 142 The PCRE_UTF8 option is set when the regular expression is passed for 143 compilation to the native function. This causes the pattern itself and all data 144 strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8 145 is not part of the POSIX standard. 146 </P> 147 <P> 148 In the absence of these flags, no options are passed to the native function. 149 This means the the regex is compiled with PCRE default semantics. In 150 particular, the way it handles newline characters in the subject string is the 151 Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only 152 <i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way 153 newlines are matched by . (they are not) or by a negative class such as [^a] 154 (they are). 155 </P> 156 <P> 157 The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The 158 <i>preg</i> structure is filled in on success, and one member of the structure 159 is public: <i>re_nsub</i> contains the number of capturing subpatterns in 160 the regular expression. Various error codes are defined in the header file. 161 </P> 162 <P> 163 NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to 164 use the contents of the <i>preg</i> structure. If, for example, you pass it to 165 <b>regexec()</b>, the result is undefined and your program is likely to crash. 166 </P> 167 <br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br> 168 <P> 169 This area is not simple, because POSIX and Perl take different views of things. 170 It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never 171 intended to be a POSIX engine. The following table lists the different 172 possibilities for matching newline characters in PCRE: 173 <pre> 174 Default Change with 175 176 . matches newline no PCRE_DOTALL 177 newline matches [^a] yes not changeable 178 $ matches \n at end yes PCRE_DOLLARENDONLY 179 $ matches \n in middle no PCRE_MULTILINE 180 ^ matches \n in middle no PCRE_MULTILINE 181 </pre> 182 This is the equivalent table for POSIX: 183 <pre> 184 Default Change with 185 186 . matches newline yes REG_NEWLINE 187 newline matches [^a] yes REG_NEWLINE 188 $ matches \n at end no REG_NEWLINE 189 $ matches \n in middle no REG_NEWLINE 190 ^ matches \n in middle no REG_NEWLINE 191 </pre> 192 PCRE's behaviour is the same as Perl's, except that there is no equivalent for 193 PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop 194 newline from matching [^a]. 195 </P> 196 <P> 197 The default POSIX newline handling can be obtained by setting PCRE_DOTALL and 198 PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the 199 REG_NEWLINE action. 200 </P> 201 <br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br> 202 <P> 203 The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i> 204 against a given <i>string</i>, which is by default terminated by a zero byte 205 (but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can 206 be: 207 <pre> 208 REG_NOTBOL 209 </pre> 210 The PCRE_NOTBOL option is set when calling the underlying PCRE matching 211 function. 212 <pre> 213 REG_NOTEMPTY 214 </pre> 215 The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching 216 function. Note that REG_NOTEMPTY is not part of the POSIX standard. However, 217 setting this option can give more POSIX-like behaviour in some situations. 218 <pre> 219 REG_NOTEOL 220 </pre> 221 The PCRE_NOTEOL option is set when calling the underlying PCRE matching 222 function. 223 <pre> 224 REG_STARTEND 225 </pre> 226 The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and 227 to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i> 228 (there need not actually be a NUL at that location), regardless of the value of 229 <i>nmatch</i>. This is a BSD extension, compatible with but not specified by 230 IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software 231 intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does 232 not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not 233 how it is matched. 234 </P> 235 <P> 236 If the pattern was compiled with the REG_NOSUB flag, no data about any matched 237 strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of 238 <b>regexec()</b> are ignored. 239 </P> 240 <P> 241 If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL, 242 no data about any matched strings is returned. 243 </P> 244 <P> 245 Otherwise,the portion of the string that was matched, and also any captured 246 substrings, are returned via the <i>pmatch</i> argument, which points to an 247 array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the 248 members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first 249 character of each substring and the offset to the first character after the end 250 of each substring, respectively. The 0th element of the vector relates to the 251 entire portion of <i>string</i> that was matched; subsequent elements relate to 252 the capturing subpatterns of the regular expression. Unused entries in the 253 array have both structure members set to -1. 254 </P> 255 <P> 256 A successful match yields a zero return; various error codes are defined in the 257 header file, of which REG_NOMATCH is the "expected" failure code. 258 </P> 259 <br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br> 260 <P> 261 The <b>regerror()</b> function maps a non-zero errorcode from either 262 <b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not 263 NULL, the error should have arisen from the use of that structure. A message 264 terminated by a binary zero is placed in <i>errbuf</i>. The length of the 265 message, including the zero, is limited to <i>errbuf_size</i>. The yield of the 266 function is the size of buffer needed to hold the whole message. 267 </P> 268 <br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br> 269 <P> 270 Compiling a regular expression causes memory to be allocated and associated 271 with the <i>preg</i> structure. The function <b>regfree()</b> frees all such 272 memory, after which <i>preg</i> may no longer be used as a compiled expression. 273 </P> 274 <br><a name="SEC8" href="#TOC1">AUTHOR</a><br> 275 <P> 276 Philip Hazel 277 <br> 278 University Computing Service 279 <br> 280 Cambridge CB2 3QH, England. 281 <br> 282 </P> 283 <br><a name="SEC9" href="#TOC1">REVISION</a><br> 284 <P> 285 Last updated: 16 May 2010 286 <br> 287 Copyright © 1997-2010 University of Cambridge. 288 <br> 289 <p> 290 Return to the <a href="index.html">PCRE index page</a>. 291 </p> 292