/vendor/pcre/doc/html/pcreposix.html

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  1. <html>
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  2. <head>
    3. 

  3. <title>pcreposix specification</title>
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  4. </head>
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  5. <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
    6. 

  6. <h1>pcreposix man page</h1>
    7. 

  7. <p>
    8. 

  8. Return to the <a href="index.html">PCRE index page</a>.
    9. 

  9. </p>
    10. 

  10. <p>
    11. 

  11. This page is part of the PCRE HTML documentation. It was generated automatically
    12. 

  12. from the original man page. If there is any nonsense in it, please consult the
    13. 

  13. man page, in case the conversion went wrong.
    14. 

  14. <br>
    15. 

  15. <ul>
    16. 

  16. <li><a name="TOC1" href="#SEC1">SYNOPSIS OF POSIX API</a>
    17. 

  17. <li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
    18. 

  18. <li><a name="TOC3" href="#SEC3">COMPILING A PATTERN</a>
    19. 

  19. <li><a name="TOC4" href="#SEC4">MATCHING NEWLINE CHARACTERS</a>
    20. 

  20. <li><a name="TOC5" href="#SEC5">MATCHING A PATTERN</a>
    21. 

  21. <li><a name="TOC6" href="#SEC6">ERROR MESSAGES</a>
    22. 

  22. <li><a name="TOC7" href="#SEC7">MEMORY USAGE</a>
    23. 

  23. <li><a name="TOC8" href="#SEC8">AUTHOR</a>
    24. 

  24. <li><a name="TOC9" href="#SEC9">REVISION</a>
    25. 

  25. </ul>
    26. 

  26. <br><a name="SEC1" href="#TOC1">SYNOPSIS OF POSIX API</a><br>
    27. 

  27. <P>
    28. 

  28. <b>#include &#60;pcreposix.h&#62;</b>
    29. 

  29. </P>
    30. 

  30. <P>
    31. 

  31. <b>int regcomp(regex_t *<i>preg</i>, const char *<i>pattern</i>,</b>
    32. 

  32. <b>int <i>cflags</i>);</b>
    33. 

  33. </P>
    34. 

  34. <P>
    35. 

  35. <b>int regexec(regex_t *<i>preg</i>, const char *<i>string</i>,</b>
    36. 

  36. <b>size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b>
    37. 

  37. </P>
    38. 

  38. <P>
    39. 

  39. <b>size_t regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b>
    40. 

  40. <b>char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b>
    41. 

  41. </P>
    42. 

  42. <P>
    43. 

  43. <b>void regfree(regex_t *<i>preg</i>);</b>
    44. 

  44. </P>
    45. 

  45. <br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
    46. 

  46. <P>
    47. 

  47. This set of functions provides a POSIX-style API to the PCRE regular expression
    48. 

  48. package. See the
    49. 

  49. <a href="pcreapi.html"><b>pcreapi</b></a>
    50. 

  50. documentation for a description of PCRE's native API, which contains much
    51. 

  51. additional functionality.
    52. 

  52. </P>
    53. 

  53. <P>
    54. 

  54. The functions described here are just wrapper functions that ultimately call
    55. 

  55. the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b>
    56. 

  56. header file, and on Unix systems the library itself is called
    57. 

  57. <b>pcreposix.a</b>, so can be accessed by adding <b>-lpcreposix</b> to the
    58. 

  58. command for linking an application that uses them. Because the POSIX functions
    59. 

  59. call the native ones, it is also necessary to add <b>-lpcre</b>.
    60. 

  60. </P>
    61. 

  61. <P>
    62. 

  62. I have implemented only those option bits that can be reasonably mapped to PCRE
    63. 

  63. native options. In addition, the option REG_EXTENDED is defined with the value
    64. 

  64. zero. This has no effect, but since programs that are written to the POSIX
    65. 

  65. interface often use it, this makes it easier to slot in PCRE as a replacement
    66. 

  66. library. Other POSIX options are not even defined.
    67. 

  67. </P>
    68. 

  68. <P>
    69. 

  69. When PCRE is called via these functions, it is only the API that is POSIX-like
    70. 

  70. in style. The syntax and semantics of the regular expressions themselves are
    71. 

  71. still those of Perl, subject to the setting of various PCRE options, as
    72. 

  72. described below. "POSIX-like in style" means that the API approximates to the
    73. 

  73. POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding
    74. 

  74. domains it is probably even less compatible.
    75. 

  75. </P>
    76. 

  76. <P>
    77. 

  77. The header for these functions is supplied as <b>pcreposix.h</b> to avoid any
    78. 

  78. potential clash with other POSIX libraries. It can, of course, be renamed or
    79. 

  79. aliased as <b>regex.h</b>, which is the "correct" name. It provides two
    80. 

  80. structure types, <i>regex_t</i> for compiled internal forms, and
    81. 

  81. <i>regmatch_t</i> for returning captured substrings. It also defines some
    82. 

  82. constants whose names start with "REG_"; these are used for setting options and
    83. 

  83. identifying error codes.
    84. 

  84. </P>
    85. 

  85. <P>
    86. 

  86. </P>
    87. 

  87. <br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br>
    88. 

  88. <P>
    89. 

  89. The function <b>regcomp()</b> is called to compile a pattern into an
    90. 

  90. internal form. The pattern is a C string terminated by a binary zero, and
    91. 

  91. is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer
    92. 

  92. to a <b>regex_t</b> structure that is used as a base for storing information
    93. 

  93. about the compiled regular expression.
    94. 

  94. </P>
    95. 

  95. <P>
    96. 

  96. The argument <i>cflags</i> is either zero, or contains one or more of the bits
    97. 

  97. defined by the following macros:
    98. 

  98. <pre>
    99. 

  99.   REG_DOTALL
    100. 

  100. </pre>
    101. 

  101. The PCRE_DOTALL option is set when the regular expression is passed for
    102. 

  102. compilation to the native function. Note that REG_DOTALL is not part of the
    103. 

  103. POSIX standard.
    104. 

  104. <pre>
    105. 

  105.   REG_ICASE
    106. 

  106. </pre>
    107. 

  107. The PCRE_CASELESS option is set when the regular expression is passed for
    108. 

  108. compilation to the native function.
    109. 

  109. <pre>
    110. 

  110.   REG_NEWLINE
    111. 

  111. </pre>
    112. 

  112. The PCRE_MULTILINE option is set when the regular expression is passed for
    113. 

  113. compilation to the native function. Note that this does <i>not</i> mimic the
    114. 

  114. defined POSIX behaviour for REG_NEWLINE (see the following section).
    115. 

  115. <pre>
    116. 

  116.   REG_NOSUB
    117. 

  117. </pre>
    118. 

  118. The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed
    119. 

  119. for compilation to the native function. In addition, when a pattern that is
    120. 

  120. compiled with this flag is passed to <b>regexec()</b> for matching, the
    121. 

  121. <i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings
    122. 

  122. are returned.
    123. 

  123. <pre>
    124. 

  124.   REG_UTF8
    125. 

  125. </pre>
    126. 

  126. The PCRE_UTF8 option is set when the regular expression is passed for
    127. 

  127. compilation to the native function. This causes the pattern itself and all data
    128. 

  128. strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8
    129. 

  129. is not part of the POSIX standard.
    130. 

  130. </P>
    131. 

  131. <P>
    132. 

  132. In the absence of these flags, no options are passed to the native function.
    133. 

  133. This means the the regex is compiled with PCRE default semantics. In
    134. 

  134. particular, the way it handles newline characters in the subject string is the
    135. 

  135. Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only
    136. 

  136. <i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way
    137. 

  137. newlines are matched by . (they aren't) or by a negative class such as [^a]
    138. 

  138. (they are).
    139. 

  139. </P>
    140. 

  140. <P>
    141. 

  141. The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The
    142. 

  142. <i>preg</i> structure is filled in on success, and one member of the structure
    143. 

  143. is public: <i>re_nsub</i> contains the number of capturing subpatterns in
    144. 

  144. the regular expression. Various error codes are defined in the header file.
    145. 

  145. </P>
    146. 

  146. <br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br>
    147. 

  147. <P>
    148. 

  148. This area is not simple, because POSIX and Perl take different views of things.
    149. 

  149. It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never
    150. 

  150. intended to be a POSIX engine. The following table lists the different
    151. 

  151. possibilities for matching newline characters in PCRE:
    152. 

  152. <pre>
    153. 

  153.                           Default   Change with
    154. 

  154. 

  155.   . matches newline          no     PCRE_DOTALL
    156. 

  156.   newline matches [^a]       yes    not changeable
    157. 

  157.   $ matches \n at end        yes    PCRE_DOLLARENDONLY
    158. 

  158.   $ matches \n in middle     no     PCRE_MULTILINE
    159. 

  159.   ^ matches \n in middle     no     PCRE_MULTILINE
    160. 

  160. </pre>
    161. 

  161. This is the equivalent table for POSIX:
    162. 

  162. <pre>
    163. 

  163.                           Default   Change with
    164. 

  164. 

  165.   . matches newline          yes    REG_NEWLINE
    166. 

  166.   newline matches [^a]       yes    REG_NEWLINE
    167. 

  167.   $ matches \n at end        no     REG_NEWLINE
    168. 

  168.   $ matches \n in middle     no     REG_NEWLINE
    169. 

  169.   ^ matches \n in middle     no     REG_NEWLINE
    170. 

  170. </pre>
    171. 

  171. PCRE's behaviour is the same as Perl's, except that there is no equivalent for
    172. 

  172. PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop
    173. 

  173. newline from matching [^a].
    174. 

  174. </P>
    175. 

  175. <P>
    176. 

  176. The default POSIX newline handling can be obtained by setting PCRE_DOTALL and
    177. 

  177. PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the
    178. 

  178. REG_NEWLINE action.
    179. 

  179. </P>
    180. 

  180. <br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br>
    181. 

  181. <P>
    182. 

  182. The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i>
    183. 

  183. against a given <i>string</i>, which is by default terminated by a zero byte
    184. 

  184. (but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can
    185. 

  185. be:
    186. 

  186. <pre>
    187. 

  187.   REG_NOTBOL
    188. 

  188. </pre>
    189. 

  189. The PCRE_NOTBOL option is set when calling the underlying PCRE matching
    190. 

  190. function.
    191. 

  191. <pre>
    192. 

  192.   REG_NOTEOL
    193. 

  193. </pre>
    194. 

  194. The PCRE_NOTEOL option is set when calling the underlying PCRE matching
    195. 

  195. function.
    196. 

  196. <pre>
    197. 

  197.   REG_STARTEND
    198. 

  198. </pre>
    199. 

  199. The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and
    200. 

  200. to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i>
    201. 

  201. (there need not actually be a NUL at that location), regardless of the value of
    202. 

  202. <i>nmatch</i>. This is a BSD extension, compatible with but not specified by
    203. 

  203. IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software
    204. 

  204. intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does
    205. 

  205. not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not
    206. 

  206. how it is matched.
    207. 

  207. </P>
    208. 

  208. <P>
    209. 

  209. If the pattern was compiled with the REG_NOSUB flag, no data about any matched
    210. 

  210. strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of
    211. 

  211. <b>regexec()</b> are ignored.
    212. 

  212. </P>
    213. 

  213. <P>
    214. 

  214. Otherwise,the portion of the string that was matched, and also any captured
    215. 

  215. substrings, are returned via the <i>pmatch</i> argument, which points to an
    216. 

  216. array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the
    217. 

  217. members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first
    218. 

  218. character of each substring and the offset to the first character after the end
    219. 

  219. of each substring, respectively. The 0th element of the vector relates to the
    220. 

  220. entire portion of <i>string</i> that was matched; subsequent elements relate to
    221. 

  221. the capturing subpatterns of the regular expression. Unused entries in the
    222. 

  222. array have both structure members set to -1.
    223. 

  223. </P>
    224. 

  224. <P>
    225. 

  225. A successful match yields a zero return; various error codes are defined in the
    226. 

  226. header file, of which REG_NOMATCH is the "expected" failure code.
    227. 

  227. </P>
    228. 

  228. <br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br>
    229. 

  229. <P>
    230. 

  230. The <b>regerror()</b> function maps a non-zero errorcode from either
    231. 

  231. <b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not
    232. 

  232. NULL, the error should have arisen from the use of that structure. A message
    233. 

  233. terminated by a binary zero is placed in <i>errbuf</i>. The length of the
    234. 

  234. message, including the zero, is limited to <i>errbuf_size</i>. The yield of the
    235. 

  235. function is the size of buffer needed to hold the whole message.
    236. 

  236. </P>
    237. 

  237. <br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br>
    238. 

  238. <P>
    239. 

  239. Compiling a regular expression causes memory to be allocated and associated
    240. 

  240. with the <i>preg</i> structure. The function <b>regfree()</b> frees all such
    241. 

  241. memory, after which <i>preg</i> may no longer be used as a compiled expression.
    242. 

  242. </P>
    243. 

  243. <br><a name="SEC8" href="#TOC1">AUTHOR</a><br>
    244. 

  244. <P>
    245. 

  245. Philip Hazel
    246. 

  246. <br>
    247. 

  247. University Computing Service
    248. 

  248. <br>
    249. 

  249. Cambridge CB2 3QH, England.
    250. 

  250. <br>
    251. 

  251. </P>
    252. 

  252. <br><a name="SEC9" href="#TOC1">REVISION</a><br>
    253. 

  253. <P>
    254. 

  254. Last updated: 05 April 2008
    255. 

  255. <br>
    256. 

  256. Copyright &copy; 1997-2008 University of Cambridge.
    257. 

  257. <br>
    258. 

  258. <p>
    259. 

  259. Return to the <a href="index.html">PCRE index page</a>.
    260. 

  260. </p>
    261.