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