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! 2: <head>
! 3: <title>pcreposix specification</title>
! 4: </head>
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! 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>
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