doc/html/pcreposix.html

<html>
<head>
<title>pcreposix specification</title>
</head>
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
<h1>pcreposix man page</h1>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
<p>
This page is part of the PCRE HTML documentation. It was generated automatically
from the original man page. If there is any nonsense in it, please consult the
man page, in case the conversion went wrong.
<br>
<ul>
<li><a name="TOC1" href="#SEC1">SYNOPSIS OF POSIX API</a>
<li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
<li><a name="TOC3" href="#SEC3">COMPILING A PATTERN</a>
<li><a name="TOC4" href="#SEC4">MATCHING NEWLINE CHARACTERS</a>
<li><a name="TOC5" href="#SEC5">MATCHING A PATTERN</a>
<li><a name="TOC6" href="#SEC6">ERROR MESSAGES</a>
<li><a name="TOC7" href="#SEC7">MEMORY USAGE</a>
<li><a name="TOC8" href="#SEC8">AUTHOR</a>
<li><a name="TOC9" href="#SEC9">REVISION</a>
</ul>
<br><a name="SEC1" href="#TOC1">SYNOPSIS OF POSIX API</a><br>
<P>
<b>#include &#60;pcreposix.h&#62;</b>
</P>
<P>
<b>int regcomp(regex_t *<i>preg</i>, const char *<i>pattern</i>,</b>
<b>int <i>cflags</i>);</b>
</P>
<P>
<b>int regexec(regex_t *<i>preg</i>, const char *<i>string</i>,</b>
<b>size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b>
</P>
<P>
<b>size_t regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b>
<b>char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b>
</P>
<P>
<b>void regfree(regex_t *<i>preg</i>);</b>
</P>
<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
<P>
This set of functions provides a POSIX-style API to the PCRE regular expression
package. See the
<a href="pcreapi.html"><b>pcreapi</b></a>
documentation for a description of PCRE's native API, which contains much
additional functionality.
</P>
<P>
The functions described here are just wrapper functions that ultimately call
the PCRE native API. Their prototypes are defined in the <b>pcreposix.h</b>
header file, and on Unix systems the library itself is called
<b>pcreposix.a</b>, so can be accessed by adding <b>-lpcreposix</b> to the
command for linking an application that uses them. Because the POSIX functions
call the native ones, it is also necessary to add <b>-lpcre</b>.
</P>
<P>
I have implemented only those POSIX option bits that can be reasonably mapped
to PCRE native options. In addition, the option REG_EXTENDED is defined with
the value zero. This has no effect, but since programs that are written to the
POSIX interface often use it, this makes it easier to slot in PCRE as a
replacement library. Other POSIX options are not even defined.
</P>
<P>
There are also some other options that are not defined by POSIX. These have
been added at the request of users who want to make use of certain
PCRE-specific features via the POSIX calling interface.
</P>
<P>
When PCRE is called via these functions, it is only the API that is POSIX-like
in style. The syntax and semantics of the regular expressions themselves are
still those of Perl, subject to the setting of various PCRE options, as
described below. "POSIX-like in style" means that the API approximates to the
POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding
domains it is probably even less compatible.
</P>
<P>
The header for these functions is supplied as <b>pcreposix.h</b> to avoid any
potential clash with other POSIX libraries. It can, of course, be renamed or
aliased as <b>regex.h</b>, which is the "correct" name. It provides two
structure types, <i>regex_t</i> for compiled internal forms, and
<i>regmatch_t</i> for returning captured substrings. It also defines some
constants whose names start with "REG_"; these are used for setting options and
identifying error codes.
</P>
<P>
</P>
<br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br>
<P>
The function <b>regcomp()</b> is called to compile a pattern into an
internal form. The pattern is a C string terminated by a binary zero, and
is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer
to a <b>regex_t</b> structure that is used as a base for storing information
about the compiled regular expression.
</P>
<P>
The argument <i>cflags</i> is either zero, or contains one or more of the bits
defined by the following macros:
<pre>
  REG_DOTALL
</pre>
The PCRE_DOTALL option is set when the regular expression is passed for
compilation to the native function. Note that REG_DOTALL is not part of the
POSIX standard.
<pre>
  REG_ICASE
</pre>
The PCRE_CASELESS option is set when the regular expression is passed for
compilation to the native function.
<pre>
  REG_NEWLINE
</pre>
The PCRE_MULTILINE option is set when the regular expression is passed for
compilation to the native function. Note that this does <i>not</i> mimic the
defined POSIX behaviour for REG_NEWLINE (see the following section).
<pre>
  REG_NOSUB
</pre>
The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed
for compilation to the native function. In addition, when a pattern that is
compiled with this flag is passed to <b>regexec()</b> for matching, the
<i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings
are returned.
<pre>
  REG_UNGREEDY
</pre>
The PCRE_UNGREEDY option is set when the regular expression is passed for 
compilation to the native function. Note that REG_UNGREEDY is not part of the
POSIX standard.   
<pre>
  REG_UTF8
</pre>
The PCRE_UTF8 option is set when the regular expression is passed for
compilation to the native function. This causes the pattern itself and all data
strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8
is not part of the POSIX standard.
</P>
<P>
In the absence of these flags, no options are passed to the native function.
This means the the regex is compiled with PCRE default semantics. In
particular, the way it handles newline characters in the subject string is the
Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only
<i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way
newlines are matched by . (they are not) or by a negative class such as [^a]
(they are).
</P>
<P>
The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The
<i>preg</i> structure is filled in on success, and one member of the structure
is public: <i>re_nsub</i> contains the number of capturing subpatterns in
the regular expression. Various error codes are defined in the header file.
</P>
<P>
NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to
use the contents of the <i>preg</i> structure. If, for example, you pass it to
<b>regexec()</b>, the result is undefined and your program is likely to crash.
</P>
<br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br>
<P>
This area is not simple, because POSIX and Perl take different views of things.
It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never
intended to be a POSIX engine. The following table lists the different
possibilities for matching newline characters in PCRE:
<pre>
                          Default   Change with

  . matches newline          no     PCRE_DOTALL
  newline matches [^a]       yes    not changeable
  $ matches \n at end        yes    PCRE_DOLLARENDONLY
  $ matches \n in middle     no     PCRE_MULTILINE
  ^ matches \n in middle     no     PCRE_MULTILINE
</pre>
This is the equivalent table for POSIX:
<pre>
                          Default   Change with

  . matches newline          yes    REG_NEWLINE
  newline matches [^a]       yes    REG_NEWLINE
  $ matches \n at end        no     REG_NEWLINE
  $ matches \n in middle     no     REG_NEWLINE
  ^ matches \n in middle     no     REG_NEWLINE
</pre>
PCRE's behaviour is the same as Perl's, except that there is no equivalent for
PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop
newline from matching [^a].
</P>
<P>
The default POSIX newline handling can be obtained by setting PCRE_DOTALL and
PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the
REG_NEWLINE action.
</P>
<br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br>
<P>
The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i>
against a given <i>string</i>, which is by default terminated by a zero byte
(but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can
be:
<pre>
  REG_NOTBOL
</pre>
The PCRE_NOTBOL option is set when calling the underlying PCRE matching
function.
<pre>
  REG_NOTEMPTY
</pre>
The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching
function. Note that REG_NOTEMPTY is not part of the POSIX standard. However,
setting this option can give more POSIX-like behaviour in some situations.
<pre>
  REG_NOTEOL
</pre>
The PCRE_NOTEOL option is set when calling the underlying PCRE matching
function.
<pre>
  REG_STARTEND
</pre>
The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and
to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i>
(there need not actually be a NUL at that location), regardless of the value of
<i>nmatch</i>. This is a BSD extension, compatible with but not specified by
IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software
intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does
not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not
how it is matched.
</P>
<P>
If the pattern was compiled with the REG_NOSUB flag, no data about any matched
strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of
<b>regexec()</b> are ignored.
</P>
<P>
If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL,
no data about any matched strings is returned.
</P>
<P>
Otherwise,the portion of the string that was matched, and also any captured
substrings, are returned via the <i>pmatch</i> argument, which points to an
array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the
members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first
character of each substring and the offset to the first character after the end
of each substring, respectively. The 0th element of the vector relates to the
entire portion of <i>string</i> that was matched; subsequent elements relate to
the capturing subpatterns of the regular expression. Unused entries in the
array have both structure members set to -1.
</P>
<P>
A successful match yields a zero return; various error codes are defined in the
header file, of which REG_NOMATCH is the "expected" failure code.
</P>
<br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br>
<P>
The <b>regerror()</b> function maps a non-zero errorcode from either
<b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not
NULL, the error should have arisen from the use of that structure. A message
terminated by a binary zero is placed in <i>errbuf</i>. The length of the
message, including the zero, is limited to <i>errbuf_size</i>. The yield of the
function is the size of buffer needed to hold the whole message.
</P>
<br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br>
<P>
Compiling a regular expression causes memory to be allocated and associated
with the <i>preg</i> structure. The function <b>regfree()</b> frees all such
memory, after which <i>preg</i> may no longer be used as a compiled expression.
</P>
<br><a name="SEC8" href="#TOC1">AUTHOR</a><br>
<P>
Philip Hazel
<br>
University Computing Service
<br>
Cambridge CB2 3QH, England.
<br>
</P>
<br><a name="SEC9" href="#TOC1">REVISION</a><br>
<P>
Last updated: 02 September 2009
<br>
Copyright &copy; 1997-2009 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
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 <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	nigel	77	documentation for a description of PCRE's native API, which contains much
51			additional functionality.
52	nigel	63	</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	nigel	75	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	nigel	63	</P>
61			<P>
62	ph10	392	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	nigel	63	</P>
68			<P>
69	ph10	453	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	nigel	63	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	nigel	69	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	nigel	63	</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	nigel	75	<P>
91			</P>
92	nigel	63	<br><a name="SEC3" href="#TOC1">COMPILING A PATTERN</a><br>
93			<P>
94			The function <b>regcomp()</b> is called to compile a pattern into an
95			internal form. The pattern is a C string terminated by a binary zero, and
96			is passed in the argument <i>pattern</i>. The <i>preg</i> argument is a pointer
97	nigel	75	to a <b>regex_t</b> structure that is used as a base for storing information
98	nigel	87	about the compiled regular expression.
99	nigel	63	</P>
100			<P>
101			The argument <i>cflags</i> is either zero, or contains one or more of the bits
102			defined by the following macros:
103			<pre>
104	nigel	77	REG_DOTALL
105			</pre>
106	nigel	87	The PCRE_DOTALL option is set when the regular expression is passed for
107			compilation to the native function. Note that REG_DOTALL is not part of the
108			POSIX standard.
109	nigel	77	<pre>
110	nigel	63	REG_ICASE
111	nigel	75	</pre>
112	nigel	87	The PCRE_CASELESS option is set when the regular expression is passed for
113			compilation to the native function.
114	nigel	63	<pre>
115			REG_NEWLINE
116	nigel	75	</pre>
117	nigel	87	The PCRE_MULTILINE option is set when the regular expression is passed for
118			compilation to the native function. Note that this does <i>not</i> mimic the
119			defined POSIX behaviour for REG_NEWLINE (see the following section).
120			<pre>
121			REG_NOSUB
122			</pre>
123			The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is passed
124			for compilation to the native function. In addition, when a pattern that is
125			compiled with this flag is passed to <b>regexec()</b> for matching, the
126			<i>nmatch</i> and <i>pmatch</i> arguments are ignored, and no captured strings
127			are returned.
128			<pre>
129	ph10	453	REG_UNGREEDY
130			</pre>
131			The PCRE_UNGREEDY option is set when the regular expression is passed for
132			compilation to the native function. Note that REG_UNGREEDY is not part of the
133			POSIX standard.
134			<pre>
135	nigel	87	REG_UTF8
136			</pre>
137			The PCRE_UTF8 option is set when the regular expression is passed for
138			compilation to the native function. This causes the pattern itself and all data
139			strings used for matching it to be treated as UTF-8 strings. Note that REG_UTF8
140			is not part of the POSIX standard.
141	nigel	63	</P>
142			<P>
143			In the absence of these flags, no options are passed to the native function.
144			This means the the regex is compiled with PCRE default semantics. In
145			particular, the way it handles newline characters in the subject string is the
146			Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only
147			<i>some</i> of the effects specified for REG_NEWLINE. It does not affect the way
148	ph10	453	newlines are matched by . (they are not) or by a negative class such as [^a]
149	nigel	63	(they are).
150			</P>
151			<P>
152			The yield of <b>regcomp()</b> is zero on success, and non-zero otherwise. The
153			<i>preg</i> structure is filled in on success, and one member of the structure
154			is public: <i>re_nsub</i> contains the number of capturing subpatterns in
155			the regular expression. Various error codes are defined in the header file.
156			</P>
157	ph10	429	<P>
158			NOTE: If the yield of <b>regcomp()</b> is non-zero, you must not attempt to
159			use the contents of the <i>preg</i> structure. If, for example, you pass it to
160			<b>regexec()</b>, the result is undefined and your program is likely to crash.
161			</P>
162	nigel	63	<br><a name="SEC4" href="#TOC1">MATCHING NEWLINE CHARACTERS</a><br>
163			<P>
164			This area is not simple, because POSIX and Perl take different views of things.
165			It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never
166			intended to be a POSIX engine. The following table lists the different
167			possibilities for matching newline characters in PCRE:
168			<pre>
169			Default Change with
170	nigel	75
171	nigel	63	. matches newline no PCRE_DOTALL
172			newline matches [^a] yes not changeable
173			$ matches \n at end yes PCRE_DOLLARENDONLY
174			$ matches \n in middle no PCRE_MULTILINE
175			^ matches \n in middle no PCRE_MULTILINE
176	nigel	75	</pre>
177	nigel	63	This is the equivalent table for POSIX:
178			<pre>
179			Default Change with
180	nigel	75
181			. matches newline yes REG_NEWLINE
182			newline matches [^a] yes REG_NEWLINE
183			$ matches \n at end no REG_NEWLINE
184			$ matches \n in middle no REG_NEWLINE
185			^ matches \n in middle no REG_NEWLINE
186			</pre>
187	nigel	63	PCRE's behaviour is the same as Perl's, except that there is no equivalent for
188	nigel	75	PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop
189	nigel	63	newline from matching [^a].
190			</P>
191			<P>
192			The default POSIX newline handling can be obtained by setting PCRE_DOTALL and
193	nigel	75	PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the
194	nigel	63	REG_NEWLINE action.
195			</P>
196			<br><a name="SEC5" href="#TOC1">MATCHING A PATTERN</a><br>
197			<P>
198	nigel	75	The function <b>regexec()</b> is called to match a compiled pattern <i>preg</i>
199	ph10	345	against a given <i>string</i>, which is by default terminated by a zero byte
200			(but see REG_STARTEND below), subject to the options in <i>eflags</i>. These can
201			be:
202	nigel	63	<pre>
203			REG_NOTBOL
204	nigel	75	</pre>
205	nigel	63	The PCRE_NOTBOL option is set when calling the underlying PCRE matching
206			function.
207			<pre>
208	ph10	392	REG_NOTEMPTY
209			</pre>
210			The PCRE_NOTEMPTY option is set when calling the underlying PCRE matching
211			function. Note that REG_NOTEMPTY is not part of the POSIX standard. However,
212			setting this option can give more POSIX-like behaviour in some situations.
213			<pre>
214	nigel	63	REG_NOTEOL
215	nigel	75	</pre>
216	nigel	63	The PCRE_NOTEOL option is set when calling the underlying PCRE matching
217			function.
218	ph10	345	<pre>
219			REG_STARTEND
220			</pre>
221			The string is considered to start at <i>string</i> + <i>pmatch[0].rm_so</i> and
222			to have a terminating NUL located at <i>string</i> + <i>pmatch[0].rm_eo</i>
223			(there need not actually be a NUL at that location), regardless of the value of
224			<i>nmatch</i>. This is a BSD extension, compatible with but not specified by
225			IEEE Standard 1003.2 (POSIX.2), and should be used with caution in software
226			intended to be portable to other systems. Note that a non-zero <i>rm_so</i> does
227			not imply REG_NOTBOL; REG_STARTEND affects only the location of the string, not
228			how it is matched.
229	nigel	63	</P>
230			<P>
231	nigel	87	If the pattern was compiled with the REG_NOSUB flag, no data about any matched
232			strings is returned. The <i>nmatch</i> and <i>pmatch</i> arguments of
233			<b>regexec()</b> are ignored.
234	nigel	63	</P>
235			<P>
236	ph10	453	If the value of <i>nmatch</i> is zero, or if the value <i>pmatch</i> is NULL,
237			no data about any matched strings is returned.
238			</P>
239			<P>
240	nigel	87	Otherwise,the portion of the string that was matched, and also any captured
241			substrings, are returned via the <i>pmatch</i> argument, which points to an
242			array of <i>nmatch</i> structures of type <i>regmatch_t</i>, containing the
243			members <i>rm_so</i> and <i>rm_eo</i>. These contain the offset to the first
244			character of each substring and the offset to the first character after the end
245			of each substring, respectively. The 0th element of the vector relates to the
246			entire portion of <i>string</i> that was matched; subsequent elements relate to
247			the capturing subpatterns of the regular expression. Unused entries in the
248			array have both structure members set to -1.
249			</P>
250			<P>
251	nigel	63	A successful match yields a zero return; various error codes are defined in the
252			header file, of which REG_NOMATCH is the "expected" failure code.
253			</P>
254			<br><a name="SEC6" href="#TOC1">ERROR MESSAGES</a><br>
255			<P>
256			The <b>regerror()</b> function maps a non-zero errorcode from either
257			<b>regcomp()</b> or <b>regexec()</b> to a printable message. If <i>preg</i> is not
258			NULL, the error should have arisen from the use of that structure. A message
259			terminated by a binary zero is placed in <i>errbuf</i>. The length of the
260			message, including the zero, is limited to <i>errbuf_size</i>. The yield of the
261			function is the size of buffer needed to hold the whole message.
262			</P>
263	nigel	75	<br><a name="SEC7" href="#TOC1">MEMORY USAGE</a><br>
264	nigel	63	<P>
265			Compiling a regular expression causes memory to be allocated and associated
266			with the <i>preg</i> structure. The function <b>regfree()</b> frees all such
267			memory, after which <i>preg</i> may no longer be used as a compiled expression.
268			</P>
269			<br><a name="SEC8" href="#TOC1">AUTHOR</a><br>
270			<P>
271	nigel	77	Philip Hazel
272	nigel	63	<br>
273	ph10	99	University Computing Service
274	nigel	63	<br>
275	nigel	93	Cambridge CB2 3QH, England.
276	ph10	99	<br>
277	nigel	63	</P>
278	ph10	99	<br><a name="SEC9" href="#TOC1">REVISION</a><br>
279	nigel	63	<P>
280	ph10	453	Last updated: 02 September 2009
281	nigel	63	<br>
282	ph10	392	Copyright © 1997-2009 University of Cambridge.
283	ph10	99	<br>
284	nigel	75	<p>
285			Return to the <a href="index.html">PCRE index page</a>.
286			</p>
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