/[pcre]/code/tags/pcre-2.08/pcreposix.3
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Contents of /code/tags/pcre-2.08/pcreposix.3

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Sat Feb 24 21:39:15 2007 UTC (7 years, 1 month ago) by nigel
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Tag code/trunk as code/tags/pcre-2.08.

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 nigel 37 package. See the \fBpcre\fR documentation for a description of the native API,
30     which contains additional functionality.
31 nigel 3
32 nigel 37 The functions described here are just wrapper functions that ultimately call
33     the native API. Their prototypes are defined in the \fBpcreposix.h\fR header
34     file, and on Unix systems the library itself is called \fBpcreposix.a\fR, so
35     can be accessed by adding \fB-lpcreposix\fR to the command for linking an
36     application which uses them. Because the POSIX functions call the native ones,
37     it is also necessary to add \fR-lpcre\fR.
38    
39 nigel 3 As I am pretty ignorant about POSIX, these functions must be considered as
40     experimental. I have implemented only those option bits that can be reasonably
41     mapped to PCRE native options. Other POSIX options are not even defined. It may
42     be that it is useful to define, but ignore, other options. Feedback from more
43     knowledgeable folk may cause this kind of detail to change.
44    
45     When PCRE is called via these functions, it is only the API that is POSIX-like
46     in style. The syntax and semantics of the regular expressions themselves are
47     still those of Perl, subject to the setting of various PCRE options, as
48     described below.
49    
50     The header for these functions is supplied as \fBpcreposix.h\fR to avoid any
51     potential clash with other POSIX libraries. It can, of course, be renamed or
52     aliased as \fBregex.h\fR, which is the "correct" name. It provides two
53     structure types, \fIregex_t\fR for compiled internal forms, and
54     \fIregmatch_t\fR for returning captured substrings. It also defines some
55     constants whose names start with "REG_"; these are used for setting options and
56     identifying error codes.
57    
58    
59     .SH COMPILING A PATTERN
60    
61     The function \fBregcomp()\fR is called to compile a pattern into an
62     internal form. The pattern is a C string terminated by a binary zero, and
63     is passed in the argument \fIpattern\fR. The \fIpreg\fR argument is a pointer
64     to a regex_t structure which is used as a base for storing information about
65     the compiled expression.
66    
67     The argument \fIcflags\fR is either zero, or contains one or more of the bits
68     defined by the following macros:
69    
70     REG_ICASE
71    
72     The PCRE_CASELESS option is set when the expression is passed for compilation
73     to the native function.
74    
75     REG_NEWLINE
76    
77     The PCRE_MULTILINE option is set when the expression is passed for compilation
78     to the native function.
79    
80     The yield of \fBregcomp()\fR is zero on success, and non-zero otherwise. The
81     \fIpreg\fR structure is filled in on success, and one member of the structure
82     is publicized: \fIre_nsub\fR contains the number of capturing subpatterns in
83     the regular expression. Various error codes are defined in the header file.
84    
85    
86     .SH MATCHING A PATTERN
87     The function \fBregexec()\fR is called to match a pre-compiled pattern
88     \fIpreg\fR against a given \fIstring\fR, which is terminated by a zero byte,
89     subject to the options in \fIeflags\fR. These can be:
90    
91     REG_NOTBOL
92    
93     The PCRE_NOTBOL option is set when calling the underlying PCRE matching
94     function.
95    
96     REG_NOTEOL
97    
98     The PCRE_NOTEOL option is set when calling the underlying PCRE matching
99     function.
100    
101     The portion of the string that was matched, and also any captured substrings,
102     are returned via the \fIpmatch\fR argument, which points to an array of
103     \fInmatch\fR structures of type \fIregmatch_t\fR, containing the members
104     \fIrm_so\fR and \fIrm_eo\fR. These contain the offset to the first character of
105     each substring and the offset to the first character after the end of each
106     substring, respectively. The 0th element of the vector relates to the entire
107     portion of \fIstring\fR that was matched; subsequent elements relate to the
108     capturing subpatterns of the regular expression. Unused entries in the array
109     have both structure members set to -1.
110    
111     A successful match yields a zero return; various error codes are defined in the
112     header file, of which REG_NOMATCH is the "expected" failure code.
113    
114    
115     .SH ERROR MESSAGES
116     The \fBregerror()\fR function maps a non-zero errorcode from either
117     \fBregcomp\fR or \fBregexec\fR to a printable message. If \fIpreg\fR is not
118     NULL, the error should have arisen from the use of that structure. A message
119     terminated by a binary zero is placed in \fIerrbuf\fR. The length of the
120     message, including the zero, is limited to \fIerrbuf_size\fR. The yield of the
121     function is the size of buffer needed to hold the whole message.
122    
123    
124     .SH STORAGE
125     Compiling a regular expression causes memory to be allocated and associated
126     with the \fIpreg\fR structure. The function \fBregfree()\fR frees all such
127     memory, after which \fIpreg\fR may no longer be used as a compiled expression.
128    
129    
130     .SH AUTHOR
131     Philip Hazel <ph10@cam.ac.uk>
132     .br
133     University Computing Service,
134     .br
135     New Museums Site,
136     .br
137     Cambridge CB2 3QG, England.
138     .br
139     Phone: +44 1223 334714
140    
141 nigel 27 Copyright (c) 1997-1999 University of Cambridge.

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