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1 <HTML>
2 <HEAD>
3 <TITLE>pcreposix specification</TITLE>
4 </HEAD>
5 <body bgcolor="#FFFFFF" text="#00005A">
6 <H1>pcreposix specification</H1>
7 This HTML document has been generated automatically from the original man page.
8 If there is any nonsense in it, please consult the man page in case the
9 conversion went wrong.
10 <UL>
11 <LI><A NAME="TOC1" HREF="#SEC1">NAME</A>
12 <LI><A NAME="TOC2" HREF="#SEC2">SYNOPSIS</A>
13 <LI><A NAME="TOC3" HREF="#SEC3">DESCRIPTION</A>
14 <LI><A NAME="TOC4" HREF="#SEC4">COMPILING A PATTERN</A>
15 <LI><A NAME="TOC5" HREF="#SEC5">MATCHING A PATTERN</A>
16 <LI><A NAME="TOC6" HREF="#SEC6">ERROR MESSAGES</A>
17 <LI><A NAME="TOC7" HREF="#SEC7">STORAGE</A>
18 <LI><A NAME="TOC8" HREF="#SEC8">AUTHOR</A>
19 </UL>
20 <LI><A NAME="SEC1" HREF="#TOC1">NAME</A>
21 <P>
22 pcreposix - POSIX API for Perl-compatible regular expressions.
23 </P>
24 <LI><A NAME="SEC2" HREF="#TOC1">SYNOPSIS</A>
25 <P>
26 <B>#include &#60;pcreposix.h&#62;</B>
27 </P>
28 <P>
29 <B>int regcomp(regex_t *<I>preg</I>, const char *<I>pattern</I>,</B>
30 <B>int <I>cflags</I>);</B>
31 </P>
32 <P>
33 <B>int regexec(regex_t *<I>preg</I>, const char *<I>string</I>,</B>
34 <B>size_t <I>nmatch</I>, regmatch_t <I>pmatch</I>[], int <I>eflags</I>);</B>
35 </P>
36 <P>
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 </P>
40 <P>
41 <B>void regfree(regex_t *<I>preg</I>);</B>
42 </P>
43 <LI><A NAME="SEC3" HREF="#TOC1">DESCRIPTION</A>
44 <P>
45 This set of functions provides a POSIX-style API to the PCRE regular expression
46 package. See the <B>pcre</B> documentation for a description of the native API,
47 which contains additional functionality.
48 </P>
49 <P>
50 The functions described here are just wrapper functions that ultimately call
51 the native API. Their prototypes are defined in the <B>pcreposix.h</B> header
52 file, and on Unix systems the library itself is called <B>pcreposix.a</B>, so
53 can be accessed by adding <B>-lpcreposix</B> to the command for linking an
54 application which uses them. Because the POSIX functions call the native ones,
55 it is also necessary to add \fR-lpcre\fR.
56 </P>
57 <P>
58 I have implemented only those option bits that can be reasonably mapped to PCRE
59 native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined
60 with the value zero. They have no effect, but since programs that are written
61 to the POSIX interface often use them, this makes it easier to slot in PCRE as
62 a replacement library. Other POSIX options are not even defined.
63 </P>
64 <P>
65 When PCRE is called via these functions, it is only the API that is POSIX-like
66 in style. The syntax and semantics of the regular expressions themselves are
67 still those of Perl, subject to the setting of various PCRE options, as
68 described below.
69 </P>
70 <P>
71 The header for these functions is supplied as <B>pcreposix.h</B> to avoid any
72 potential clash with other POSIX libraries. It can, of course, be renamed or
73 aliased as <B>regex.h</B>, which is the "correct" name. It provides two
74 structure types, <I>regex_t</I> for compiled internal forms, and
75 <I>regmatch_t</I> for returning captured substrings. It also defines some
76 constants whose names start with "REG_"; these are used for setting options and
77 identifying error codes.
78 </P>
79 <LI><A NAME="SEC4" HREF="#TOC1">COMPILING A PATTERN</A>
80 <P>
81 The function <B>regcomp()</B> is called to compile a pattern into an
82 internal form. The pattern is a C string terminated by a binary zero, and
83 is passed in the argument <I>pattern</I>. The <I>preg</I> argument is a pointer
84 to a regex_t structure which is used as a base for storing information about
85 the compiled expression.
86 </P>
87 <P>
88 The argument <I>cflags</I> is either zero, or contains one or more of the bits
89 defined by the following macros:
90 </P>
91 <P>
92 <PRE>
93 REG_ICASE
94 </PRE>
95 </P>
96 <P>
97 The PCRE_CASELESS option is set when the expression is passed for compilation
98 to the native function.
99 </P>
100 <P>
101 <PRE>
102 REG_NEWLINE
103 </PRE>
104 </P>
105 <P>
106 The PCRE_MULTILINE option is set when the expression is passed for compilation
107 to the native function.
108 </P>
109 <P>
110 In the absence of these flags, no options are passed to the native function.
111 This means the the regex is compiled with PCRE default semantics. In
112 particular, the way it handles newline characters in the subject string is the
113 Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only
114 <I>some</I> of the effects specified for REG_NEWLINE. It does not affect the way
115 newlines are matched by . (they aren't) or a negative class such as [^a] (they
116 are).
117 </P>
118 <P>
119 The yield of <B>regcomp()</B> is zero on success, and non-zero otherwise. The
120 <I>preg</I> structure is filled in on success, and one member of the structure
121 is publicized: <I>re_nsub</I> contains the number of capturing subpatterns in
122 the regular expression. Various error codes are defined in the header file.
123 </P>
124 <LI><A NAME="SEC5" HREF="#TOC1">MATCHING A PATTERN</A>
125 <P>
126 The function <B>regexec()</B> is called to match a pre-compiled pattern
127 <I>preg</I> against a given <I>string</I>, which is terminated by a zero byte,
128 subject to the options in <I>eflags</I>. These can be:
129 </P>
130 <P>
131 <PRE>
132 REG_NOTBOL
133 </PRE>
134 </P>
135 <P>
136 The PCRE_NOTBOL option is set when calling the underlying PCRE matching
137 function.
138 </P>
139 <P>
140 <PRE>
141 REG_NOTEOL
142 </PRE>
143 </P>
144 <P>
145 The PCRE_NOTEOL option is set when calling the underlying PCRE matching
146 function.
147 </P>
148 <P>
149 The portion of the string that was matched, and also any captured substrings,
150 are returned via the <I>pmatch</I> argument, which points to an array of
151 <I>nmatch</I> structures of type <I>regmatch_t</I>, containing the members
152 <I>rm_so</I> and <I>rm_eo</I>. These contain the offset to the first character of
153 each substring and the offset to the first character after the end of each
154 substring, respectively. The 0th element of the vector relates to the entire
155 portion of <I>string</I> that was matched; subsequent elements relate to the
156 capturing subpatterns of the regular expression. Unused entries in the array
157 have both structure members set to -1.
158 </P>
159 <P>
160 A successful match yields a zero return; various error codes are defined in the
161 header file, of which REG_NOMATCH is the "expected" failure code.
162 </P>
163 <LI><A NAME="SEC6" HREF="#TOC1">ERROR MESSAGES</A>
164 <P>
165 The <B>regerror()</B> function maps a non-zero errorcode from either
166 <B>regcomp</B> or <B>regexec</B> to a printable message. If <I>preg</I> is not
167 NULL, the error should have arisen from the use of that structure. A message
168 terminated by a binary zero is placed in <I>errbuf</I>. The length of the
169 message, including the zero, is limited to <I>errbuf_size</I>. The yield of the
170 function is the size of buffer needed to hold the whole message.
171 </P>
172 <LI><A NAME="SEC7" HREF="#TOC1">STORAGE</A>
173 <P>
174 Compiling a regular expression causes memory to be allocated and associated
175 with the <I>preg</I> structure. The function <B>regfree()</B> frees all such
176 memory, after which <I>preg</I> may no longer be used as a compiled expression.
177 </P>
178 <LI><A NAME="SEC8" HREF="#TOC1">AUTHOR</A>
179 <P>
180 Philip Hazel &#60;ph10@cam.ac.uk&#62;
181 <BR>
182 University Computing Service,
183 <BR>
184 New Museums Site,
185 <BR>
186 Cambridge CB2 3QG, England.
187 <BR>
188 Phone: +44 1223 334714
189 </P>
190 <P>
191 Copyright (c) 1997-2000 University of Cambridge.

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