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1 nigel 3 .TH PCRE 3
2     .SH NAME
3     pcreposix - POSIX API for Perl-compatible regular expressions.
4     .SH SYNOPSIS
5     .B #include <pcreposix.h>
6     .PP
7     .SM
8     .br
9     .B int regcomp(regex_t *\fIpreg\fR, const char *\fIpattern\fR,
10     .ti +5n
11     .B int \fIcflags\fR);
12     .PP
13     .br
14     .B int regexec(regex_t *\fIpreg\fR, const char *\fIstring\fR,
15     .ti +5n
16     .B size_t \fInmatch\fR, regmatch_t \fIpmatch\fR[], int \fIeflags\fR);
17     .PP
18     .br
19     .B size_t regerror(int \fIerrcode\fR, const regex_t *\fIpreg\fR,
20     .ti +5n
21     .B char *\fIerrbuf\fR, size_t \fIerrbuf_size\fR);
22     .PP
23     .br
24     .B void regfree(regex_t *\fIpreg\fR);
25    
26    
27     .SH DESCRIPTION
28     This set of functions provides a POSIX-style API to the PCRE regular expression
29     package. See \fBpcre (3)\fR for a description of the native API, which contains
30     additional functionality. The functions described here are just wrapper
31     functions that ultimately call the native API.
32    
33     As I am pretty ignorant about POSIX, these functions must be considered as
34     experimental. I have implemented only those option bits that can be reasonably
35     mapped to PCRE native options. Other POSIX options are not even defined. It may
36     be that it is useful to define, but ignore, other options. Feedback from more
37     knowledgeable folk may cause this kind of detail to change.
38    
39     When PCRE is called via these functions, it is only the API that is POSIX-like
40     in style. The syntax and semantics of the regular expressions themselves are
41     still those of Perl, subject to the setting of various PCRE options, as
42     described below.
43    
44     The header for these functions is supplied as \fBpcreposix.h\fR to avoid any
45     potential clash with other POSIX libraries. It can, of course, be renamed or
46     aliased as \fBregex.h\fR, which is the "correct" name. It provides two
47     structure types, \fIregex_t\fR for compiled internal forms, and
48     \fIregmatch_t\fR for returning captured substrings. It also defines some
49     constants whose names start with "REG_"; these are used for setting options and
50     identifying error codes.
51    
52    
53     .SH COMPILING A PATTERN
54    
55     The function \fBregcomp()\fR is called to compile a pattern into an
56     internal form. The pattern is a C string terminated by a binary zero, and
57     is passed in the argument \fIpattern\fR. The \fIpreg\fR argument is a pointer
58     to a regex_t structure which is used as a base for storing information about
59     the compiled expression.
60    
61     The argument \fIcflags\fR is either zero, or contains one or more of the bits
62     defined by the following macros:
63    
64     REG_ICASE
65    
66     The PCRE_CASELESS option is set when the expression is passed for compilation
67     to the native function.
68    
69     REG_NEWLINE
70    
71     The PCRE_MULTILINE option is set when the expression is passed for compilation
72     to the native function.
73    
74     The yield of \fBregcomp()\fR is zero on success, and non-zero otherwise. The
75     \fIpreg\fR structure is filled in on success, and one member of the structure
76     is publicized: \fIre_nsub\fR contains the number of capturing subpatterns in
77     the regular expression. Various error codes are defined in the header file.
78    
79    
80     .SH MATCHING A PATTERN
81     The function \fBregexec()\fR is called to match a pre-compiled pattern
82     \fIpreg\fR against a given \fIstring\fR, which is terminated by a zero byte,
83     subject to the options in \fIeflags\fR. These can be:
84    
85     REG_NOTBOL
86    
87     The PCRE_NOTBOL option is set when calling the underlying PCRE matching
88     function.
89    
90     REG_NOTEOL
91    
92     The PCRE_NOTEOL option is set when calling the underlying PCRE matching
93     function.
94    
95     The portion of the string that was matched, and also any captured substrings,
96     are returned via the \fIpmatch\fR argument, which points to an array of
97     \fInmatch\fR structures of type \fIregmatch_t\fR, containing the members
98     \fIrm_so\fR and \fIrm_eo\fR. These contain the offset to the first character of
99     each substring and the offset to the first character after the end of each
100     substring, respectively. The 0th element of the vector relates to the entire
101     portion of \fIstring\fR that was matched; subsequent elements relate to the
102     capturing subpatterns of the regular expression. Unused entries in the array
103     have both structure members set to -1.
104    
105     A successful match yields a zero return; various error codes are defined in the
106     header file, of which REG_NOMATCH is the "expected" failure code.
107    
108    
109     .SH ERROR MESSAGES
110     The \fBregerror()\fR function maps a non-zero errorcode from either
111     \fBregcomp\fR or \fBregexec\fR to a printable message. If \fIpreg\fR is not
112     NULL, the error should have arisen from the use of that structure. A message
113     terminated by a binary zero is placed in \fIerrbuf\fR. The length of the
114     message, including the zero, is limited to \fIerrbuf_size\fR. The yield of the
115     function is the size of buffer needed to hold the whole message.
116    
117    
118     .SH STORAGE
119     Compiling a regular expression causes memory to be allocated and associated
120     with the \fIpreg\fR structure. The function \fBregfree()\fR frees all such
121     memory, after which \fIpreg\fR may no longer be used as a compiled expression.
122    
123    
124     .SH AUTHOR
125     Philip Hazel <ph10@cam.ac.uk>
126     .br
127     University Computing Service,
128     .br
129     New Museums Site,
130     .br
131     Cambridge CB2 3QG, England.
132     .br
133     Phone: +44 1223 334714
134    
135 nigel 15 Copyright (c) 1998 University of Cambridge.

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