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1 .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 Copyright (c) 1997 University of Cambridge.

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