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1 nigel 63 <html>
2     <head>
3     <title>pcreposix specification</title>
4     </head>
5     <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 nigel 75 <h1>pcreposix man page</h1>
7     <p>
8     Return to the <a href="index.html">PCRE index page</a>.
9     </p>
10 ph10 111 <p>
11 nigel 75 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 ph10 111 <br>
15 nigel 63 <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 nigel 75 <li><a name="TOC7" href="#SEC7">MEMORY USAGE</a>
23 nigel 63 <li><a name="TOC8" href="#SEC8">AUTHOR</a>
24 ph10 99 <li><a name="TOC9" href="#SEC9">REVISION</a>
25 nigel 63 </ul>
26     <br><a name="SEC1" href="#TOC1">SYNOPSIS OF POSIX API</a><br>
27     <P>
28     <b>#include &#60;pcreposix.h&#62;</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 ph10 869 This set of functions provides a POSIX-style API for the PCRE regular
48     expression 8-bit library. See the
49 nigel 63 <a href="pcreapi.html"><b>pcreapi</b></a>
50 nigel 77 documentation for a description of PCRE's native API, which contains much
51 ph10 869 additional functionality. There is no POSIX-style wrapper for PCRE's 16-bit
52     library.
53 nigel 63 </P>
54     <P>
55     The functions described here are just wrapper functions that ultimately call
56     the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b>
57     header 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
59 nigel 75 command for linking an application that uses them. Because the POSIX functions
60     call the native ones, it is also necessary to add <b>-lpcre</b>.
61 nigel 63 </P>
62     <P>
63 ph10 392 I have implemented only those POSIX option bits that can be reasonably mapped
64     to PCRE native options. In addition, the option REG_EXTENDED is defined with
65     the value zero. This has no effect, but since programs that are written to the
66     POSIX interface often use it, this makes it easier to slot in PCRE as a
67     replacement library. Other POSIX options are not even defined.
68 nigel 63 </P>
69     <P>
70 ph10 453 There are also some other options that are not defined by POSIX. These have
71     been added at the request of users who want to make use of certain
72     PCRE-specific features via the POSIX calling interface.
73     </P>
74     <P>
75 nigel 63 When PCRE is called via these functions, it is only the API that is POSIX-like
76     in style. The syntax and semantics of the regular expressions themselves are
77     still those of Perl, subject to the setting of various PCRE options, as
78 nigel 69 described below. "POSIX-like in style" means that the API approximates to the
79     POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding
80     domains it is probably even less compatible.
81 nigel 63 </P>
82     <P>
83     The header for these functions is supplied as <b>pcreposix.h</b> to avoid any
84     potential clash with other POSIX libraries. It can, of course, be renamed or
85     aliased as <b>regex.h</b>, which is the "correct" name. It provides two
86     structure types, <i>regex_t</i> for compiled internal forms, and
87     <i>regmatch_t</i> for returning captured substrings. It also defines some
88     constants whose names start with "REG_"; these are used for setting options and
89     identifying error codes.
90     </P>
91     <br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br>
92     <P>
93     The function <b>regcomp()</b> is called to compile a pattern into an
94     internal form. The pattern is a C string terminated by a binary zero, and
95     is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer
96 nigel 75 to a <b>regex_t</b> structure that is used as a base for storing information
97 nigel 87 about the compiled regular expression.
98 nigel 63 </P>
99     <P>
100     The argument <i>cflags</i> is either zero, or contains one or more of the bits
101     defined by the following macros:
102     <pre>
103 nigel 77 REG_DOTALL
104     </pre>
105 nigel 87 The PCRE_DOTALL option is set when the regular expression is passed for
106     compilation to the native function. Note that REG_DOTALL is not part of the
107     POSIX standard.
108 nigel 77 <pre>
109 nigel 63 REG_ICASE
110 nigel 75 </pre>
111 nigel 87 The PCRE_CASELESS option is set when the regular expression is passed for
112     compilation to the native function.
113 nigel 63 <pre>
115 nigel 75 </pre>
116 nigel 87 The PCRE_MULTILINE option is set when the regular expression is passed for
117     compilation to the native function. Note that this does <i>not</i> mimic the
118     defined POSIX behaviour for REG_NEWLINE (see the following section).
119     <pre>
120     REG_NOSUB
121     </pre>
122     The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed
123     for compilation to the native function. In addition, when a pattern that is
124     compiled 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
126     are returned.
127     <pre>
128 ph10 535 REG_UCP
129     </pre>
130     The PCRE_UCP option is set when the regular expression is passed for
131     compilation to the native function. This causes PCRE to use Unicode properties
132     when matchine \d, \w, etc., instead of just recognizing ASCII values. Note
133     that REG_UTF8 is not part of the POSIX standard.
134     <pre>
135 ph10 453 REG_UNGREEDY
136     </pre>
137 ph10 461 The PCRE_UNGREEDY option is set when the regular expression is passed for
138 ph10 453 compilation to the native function. Note that REG_UNGREEDY is not part of the
139 ph10 461 POSIX standard.
140 ph10 453 <pre>
141 nigel 87 REG_UTF8
142     </pre>
143     The PCRE_UTF8 option is set when the regular expression is passed for
144     compilation to the native function. This causes the pattern itself and all data
145     strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8
146     is not part of the POSIX standard.
147 nigel 63 </P>
148     <P>
149     In the absence of these flags, no options are passed to the native function.
150     This means the the regex is compiled with PCRE default semantics. In
151     particular, the way it handles newline characters in the subject string is the
152     Perl 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
154 ph10 453 newlines are matched by . (they are not) or by a negative class such as [^a]
155 nigel 63 (they are).
156     </P>
157     <P>
158     The 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
160     is public: <i>re_nsub</i> contains the number of capturing subpatterns in
161     the regular expression. Various error codes are defined in the header file.
162     </P>
163 ph10 429 <P>
164     NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to
165     use 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 nigel 63 <br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br>
169     <P>
170     This area is not simple, because POSIX and Perl take different views of things.
171     It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never
172     intended to be a POSIX engine. The following table lists the different
173     possibilities for matching newline characters in PCRE:
174     <pre>
175     Default Change with
176 nigel 75
177 nigel 63 . 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 nigel 75 </pre>
183 nigel 63 This is the equivalent table for POSIX:
184     <pre>
185     Default Change with
186 nigel 75
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>
193 nigel 63 PCRE's behaviour is the same as Perl's, except that there is no equivalent for
194 nigel 75 PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop
195 nigel 63 newline from matching [^a].
196     </P>
197     <P>
198     The default POSIX newline handling can be obtained by setting PCRE_DOTALL and
199 nigel 75 PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the
200 nigel 63 REG_NEWLINE action.
201     </P>
202     <br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br>
203     <P>
204 nigel 75 The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i>
205 ph10 345 against 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
207     be:
208 nigel 63 <pre>
209     REG_NOTBOL
210 nigel 75 </pre>
211 nigel 63 The PCRE_NOTBOL option is set when calling the underlying PCRE matching
212     function.
213     <pre>
214 ph10 392 REG_NOTEMPTY
215     </pre>
216     The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching
217     function. Note that REG_NOTEMPTY is not part of the POSIX standard. However,
218     setting this option can give more POSIX-like behaviour in some situations.
219     <pre>
220 nigel 63 REG_NOTEOL
221 nigel 75 </pre>
222 nigel 63 The PCRE_NOTEOL option is set when calling the underlying PCRE matching
223     function.
224 ph10 345 <pre>
226     </pre>
227     The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and
228     to 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
231     IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software
232     intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does
233     not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not
234     how it is matched.
235 nigel 63 </P>
236     <P>
237 nigel 87 If the pattern was compiled with the REG_NOSUB flag, no data about any matched
238     strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of
239     <b>regexec()</b> are ignored.
240 nigel 63 </P>
241     <P>
242 ph10 453 If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL,
243     no data about any matched strings is returned.
244     </P>
245     <P>
246 nigel 87 Otherwise,the portion of the string that was matched, and also any captured
247     substrings, are returned via the <i>pmatch</i> argument, which points to an
248     array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the
249     members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first
250     character of each substring and the offset to the first character after the end
251     of each substring, respectively. The 0th element of the vector relates to the
252     entire portion of <i>string</i> that was matched; subsequent elements relate to
253     the capturing subpatterns of the regular expression. Unused entries in the
254     array have both structure members set to -1.
255     </P>
256     <P>
257 nigel 63 A successful match yields a zero return; various error codes are defined in the
258     header 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>
262     The <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
264     NULL, the error should have arisen from the use of that structure. A message
265     terminated by a binary zero is placed in <i>errbuf</i>. The length of the
266     message, including the zero, is limited to <i>errbuf_size</i>. The yield of the
267     function is the size of buffer needed to hold the whole message.
268     </P>
269 nigel 75 <br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br>
270 nigel 63 <P>
271     Compiling a regular expression causes memory to be allocated and associated
272     with the <i>preg</i> structure. The function <b>regfree()</b> frees all such
273     memory, 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>
277 nigel 77 Philip Hazel
278 nigel 63 <br>
279 ph10 99 University Computing Service
280 nigel 63 <br>
281 nigel 93 Cambridge CB2 3QH, England.
282 ph10 99 <br>
283 nigel 63 </P>
284 ph10 99 <br><a name="SEC9" href="#TOC1">REVISION</a><br>
285 nigel 63 <P>
286 ph10 869 Last updated: 09 January 2012
287 nigel 63 <br>
288 ph10 869 Copyright &copy; 1997-2012 University of Cambridge.
289 ph10 99 <br>
290 nigel 75 <p>
291     Return to the <a href="index.html">PCRE index page</a>.
292     </p>


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