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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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