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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 As I am pretty ignorant about POSIX, these functions must be considered as
59 experimental. I have implemented only those option bits that can be reasonably
60 mapped to PCRE native options. Other POSIX options are not even defined. It may
61 be that it is useful to define, but ignore, other options. Feedback from more
62 knowledgeable folk may cause this kind of detail to change.
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 The yield of <B>regcomp()</B> is zero on success, and non-zero otherwise. The
111 <I>preg</I> structure is filled in on success, and one member of the structure
112 is publicized: <I>re_nsub</I> contains the number of capturing subpatterns in
113 the regular expression. Various error codes are defined in the header file.
114 </P>
115 <LI><A NAME="SEC5" HREF="#TOC1">MATCHING A PATTERN</A>
116 <P>
117 The function <B>regexec()</B> is called to match a pre-compiled pattern
118 <I>preg</I> against a given <I>string</I>, which is terminated by a zero byte,
119 subject to the options in <I>eflags</I>. These can be:
120 </P>
121 <P>
122 <PRE>
123 REG_NOTBOL
124 </PRE>
125 </P>
126 <P>
127 The PCRE_NOTBOL option is set when calling the underlying PCRE matching
128 function.
129 </P>
130 <P>
131 <PRE>
132 REG_NOTEOL
133 </PRE>
134 </P>
135 <P>
136 The PCRE_NOTEOL option is set when calling the underlying PCRE matching
137 function.
138 </P>
139 <P>
140 The portion of the string that was matched, and also any captured substrings,
141 are returned via the <I>pmatch</I> argument, which points to an array of
142 <I>nmatch</I> structures of type <I>regmatch_t</I>, containing the members
143 <I>rm_so</I> and <I>rm_eo</I>. These contain the offset to the first character of
144 each substring and the offset to the first character after the end of each
145 substring, respectively. The 0th element of the vector relates to the entire
146 portion of <I>string</I> that was matched; subsequent elements relate to the
147 capturing subpatterns of the regular expression. Unused entries in the array
148 have both structure members set to -1.
149 </P>
150 <P>
151 A successful match yields a zero return; various error codes are defined in the
152 header file, of which REG_NOMATCH is the "expected" failure code.
153 </P>
154 <LI><A NAME="SEC6" HREF="#TOC1">ERROR MESSAGES</A>
155 <P>
156 The <B>regerror()</B> function maps a non-zero errorcode from either
157 <B>regcomp</B> or <B>regexec</B> to a printable message. If <I>preg</I> is not
158 NULL, the error should have arisen from the use of that structure. A message
159 terminated by a binary zero is placed in <I>errbuf</I>. The length of the
160 message, including the zero, is limited to <I>errbuf_size</I>. The yield of the
161 function is the size of buffer needed to hold the whole message.
162 </P>
163 <LI><A NAME="SEC7" HREF="#TOC1">STORAGE</A>
164 <P>
165 Compiling a regular expression causes memory to be allocated and associated
166 with the <I>preg</I> structure. The function <B>regfree()</B> frees all such
167 memory, after which <I>preg</I> may no longer be used as a compiled expression.
168 </P>
169 <LI><A NAME="SEC8" HREF="#TOC1">AUTHOR</A>
170 <P>
171 Philip Hazel &#60;ph10@cam.ac.uk&#62;
172 <BR>
173 University Computing Service,
174 <BR>
175 New Museums Site,
176 <BR>
177 Cambridge CB2 3QG, England.
178 <BR>
179 Phone: +44 1223 334714
180 </P>
181 <P>
182 Copyright (c) 1997-1999 University of Cambridge.

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