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1  .TH PCRE 3  .TH PCRE 3
2  .SH NAME  .SH NAME
3  pcreposix - POSIX API for Perl-compatible regular expressions.  PCRE - Perl-compatible regular expressions.
4  .SH SYNOPSIS  .SH "SYNOPSIS OF POSIX API"
5    .rs
6    .sp
7  .B #include <pcreposix.h>  .B #include <pcreposix.h>
8  .PP  .PP
9  .SM  .SM
10  .br  .br
11  .B int regcomp(regex_t *\fIpreg\fR, const char *\fIpattern\fR,  .B int regcomp(regex_t *\fIpreg\fP, const char *\fIpattern\fP,
12  .ti +5n  .ti +5n
13  .B int \fIcflags\fR);  .B int \fIcflags\fP);
14  .PP  .PP
15  .br  .br
16  .B int regexec(regex_t *\fIpreg\fR, const char *\fIstring\fR,  .B int regexec(regex_t *\fIpreg\fP, const char *\fIstring\fP,
17  .ti +5n  .ti +5n
18  .B size_t \fInmatch\fR, regmatch_t \fIpmatch\fR[], int \fIeflags\fR);  .B size_t \fInmatch\fP, regmatch_t \fIpmatch\fP[], int \fIeflags\fP);
19  .PP  .PP
20  .br  .br
21  .B size_t regerror(int \fIerrcode\fR, const regex_t *\fIpreg\fR,  .B size_t regerror(int \fIerrcode\fP, const regex_t *\fIpreg\fP,
22  .ti +5n  .ti +5n
23  .B char *\fIerrbuf\fR, size_t \fIerrbuf_size\fR);  .B char *\fIerrbuf\fP, size_t \fIerrbuf_size\fP);
24  .PP  .PP
25  .br  .br
26  .B void regfree(regex_t *\fIpreg\fR);  .B void regfree(regex_t *\fIpreg\fP);
27    .
   
28  .SH DESCRIPTION  .SH DESCRIPTION
29    .rs
30    .sp
31  This set of functions provides a POSIX-style API to the PCRE regular expression  This set of functions provides a POSIX-style API to the PCRE regular expression
32  package. See the \fBpcre\fR documentation for a description of the native API,  package. See the
33  which contains additional functionality.  .\" HREF
34    \fBpcreapi\fP
35    .\"
36    documentation for a description of PCRE's native API, which contains additional
37    functionality.
38    .P
39  The functions described here are just wrapper functions that ultimately call  The functions described here are just wrapper functions that ultimately call
40  the native API. Their prototypes are defined in the \fBpcreposix.h\fR header  the PCRE native API. Their prototypes are defined in the \fBpcreposix.h\fP
41  file, and on Unix systems the library itself is called \fBpcreposix.a\fR, so  header file, and on Unix systems the library itself is called
42  can be accessed by adding \fB-lpcreposix\fR to the command for linking an  \fBpcreposix.a\fP, so can be accessed by adding \fB-lpcreposix\fP to the
43  application which uses them. Because the POSIX functions call the native ones,  command for linking an application that uses them. Because the POSIX functions
44  it is also necessary to add \fR-lpcre\fR.  call the native ones, it is also necessary to add \fB-lpcre\fP.
45    .P
46  I have implemented only those option bits that can be reasonably mapped to PCRE  I have implemented only those option bits that can be reasonably mapped to PCRE
47  native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined  native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined
48  with the value zero. They have no effect, but since programs that are written  with the value zero. They have no effect, but since programs that are written
49  to the POSIX interface often use them, this makes it easier to slot in PCRE as  to the POSIX interface often use them, this makes it easier to slot in PCRE as
50  a replacement library. Other POSIX options are not even defined.  a replacement library. Other POSIX options are not even defined.
51    .P
52  When PCRE is called via these functions, it is only the API that is POSIX-like  When PCRE is called via these functions, it is only the API that is POSIX-like
53  in style. The syntax and semantics of the regular expressions themselves are  in style. The syntax and semantics of the regular expressions themselves are
54  still those of Perl, subject to the setting of various PCRE options, as  still those of Perl, subject to the setting of various PCRE options, as
55  described below.  described below. "POSIX-like in style" means that the API approximates to the
56    POSIX definition; it is not fully POSIX-compatible, and in multi-byte encoding
57  The header for these functions is supplied as \fBpcreposix.h\fR to avoid any  domains it is probably even less compatible.
58    .P
59    The header for these functions is supplied as \fBpcreposix.h\fP to avoid any
60  potential clash with other POSIX libraries. It can, of course, be renamed or  potential clash with other POSIX libraries. It can, of course, be renamed or
61  aliased as \fBregex.h\fR, which is the "correct" name. It provides two  aliased as \fBregex.h\fP, which is the "correct" name. It provides two
62  structure types, \fIregex_t\fR for compiled internal forms, and  structure types, \fIregex_t\fP for compiled internal forms, and
63  \fIregmatch_t\fR for returning captured substrings. It also defines some  \fIregmatch_t\fP for returning captured substrings. It also defines some
64  constants whose names start with "REG_"; these are used for setting options and  constants whose names start with "REG_"; these are used for setting options and
65  identifying error codes.  identifying error codes.
66    .P
67    .SH "COMPILING A PATTERN"
68  .SH COMPILING A PATTERN  .rs
69    .sp
70  The function \fBregcomp()\fR is called to compile a pattern into an  The function \fBregcomp()\fP is called to compile a pattern into an
71  internal form. The pattern is a C string terminated by a binary zero, and  internal form. The pattern is a C string terminated by a binary zero, and
72  is passed in the argument \fIpattern\fR. The \fIpreg\fR argument is a pointer  is passed in the argument \fIpattern\fP. The \fIpreg\fP argument is a pointer
73  to a regex_t structure which is used as a base for storing information about  to a \fBregex_t\fP structure that is used as a base for storing information
74  the compiled expression.  about the compiled expression.
75    .P
76  The argument \fIcflags\fR is either zero, or contains one or more of the bits  The argument \fIcflags\fP is either zero, or contains one or more of the bits
77  defined by the following macros:  defined by the following macros:
78    .sp
79    REG_ICASE    REG_ICASE
80    .sp
81  The PCRE_CASELESS option is set when the expression is passed for compilation  The PCRE_CASELESS option is set when the expression is passed for compilation
82  to the native function.  to the native function.
83    .sp
84    REG_NEWLINE    REG_NEWLINE
85    .sp
86  The PCRE_MULTILINE option is set when the expression is passed for compilation  The PCRE_MULTILINE option is set when the expression is passed for compilation
87  to the native function.  to the native function. Note that this does \fInot\fP mimic the defined POSIX
88    behaviour for REG_NEWLINE (see the following section).
89  The yield of \fBregcomp()\fR is zero on success, and non-zero otherwise. The  .P
90  \fIpreg\fR structure is filled in on success, and one member of the structure  In the absence of these flags, no options are passed to the native function.
91  is publicized: \fIre_nsub\fR contains the number of capturing subpatterns in  This means the the regex is compiled with PCRE default semantics. In
92    particular, the way it handles newline characters in the subject string is the
93    Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only
94    \fIsome\fP of the effects specified for REG_NEWLINE. It does not affect the way
95    newlines are matched by . (they aren't) or by a negative class such as [^a]
96    (they are).
97    .P
98    The yield of \fBregcomp()\fP is zero on success, and non-zero otherwise. The
99    \fIpreg\fP structure is filled in on success, and one member of the structure
100    is public: \fIre_nsub\fP contains the number of capturing subpatterns in
101  the regular expression. Various error codes are defined in the header file.  the regular expression. Various error codes are defined in the header file.
102    .
103    .
104  .SH MATCHING A PATTERN  .SH "MATCHING NEWLINE CHARACTERS"
105  The function \fBregexec()\fR is called to match a pre-compiled pattern  .rs
106  \fIpreg\fR against a given \fIstring\fR, which is terminated by a zero byte,  .sp
107  subject to the options in \fIeflags\fR. These can be:  This area is not simple, because POSIX and Perl take different views of things.
108    It is not possible to get PCRE to obey POSIX semantics, but then PCRE was never
109    intended to be a POSIX engine. The following table lists the different
110    possibilities for matching newline characters in PCRE:
111    .sp
112                              Default   Change with
113    .sp
114      . matches newline          no     PCRE_DOTALL
115      newline matches [^a]       yes    not changeable
116      $ matches \en at end        yes    PCRE_DOLLARENDONLY
117      $ matches \en in middle     no     PCRE_MULTILINE
118      ^ matches \en in middle     no     PCRE_MULTILINE
119    .sp
120    This is the equivalent table for POSIX:
121    .sp
122                              Default   Change with
123    .sp
124      . matches newline          yes    REG_NEWLINE
125      newline matches [^a]       yes    REG_NEWLINE
126      $ matches \en at end        no     REG_NEWLINE
127      $ matches \en in middle     no     REG_NEWLINE
128      ^ matches \en in middle     no     REG_NEWLINE
129    .sp
130    PCRE's behaviour is the same as Perl's, except that there is no equivalent for
131    PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is no way to stop
132    newline from matching [^a].
133    .P
134    The default POSIX newline handling can be obtained by setting PCRE_DOTALL and
135    PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE behave exactly as for the
136    REG_NEWLINE action.
137    .
138    .
139    .SH "MATCHING A PATTERN"
140    .rs
141    .sp
142    The function \fBregexec()\fP is called to match a compiled pattern \fIpreg\fP
143    against a given \fIstring\fP, which is terminated by a zero byte, subject to
144    the options in \fIeflags\fP. These can be:
145    .sp
146    REG_NOTBOL    REG_NOTBOL
147    .sp
148  The PCRE_NOTBOL option is set when calling the underlying PCRE matching  The PCRE_NOTBOL option is set when calling the underlying PCRE matching
149  function.  function.
150    .sp
151    REG_NOTEOL    REG_NOTEOL
152    .sp
153  The PCRE_NOTEOL option is set when calling the underlying PCRE matching  The PCRE_NOTEOL option is set when calling the underlying PCRE matching
154  function.  function.
155    .P
156  The portion of the string that was matched, and also any captured substrings,  The portion of the string that was matched, and also any captured substrings,
157  are returned via the \fIpmatch\fR argument, which points to an array of  are returned via the \fIpmatch\fP argument, which points to an array of
158  \fInmatch\fR structures of type \fIregmatch_t\fR, containing the members  \fInmatch\fP structures of type \fIregmatch_t\fP, containing the members
159  \fIrm_so\fR and \fIrm_eo\fR. These contain the offset to the first character of  \fIrm_so\fP and \fIrm_eo\fP. These contain the offset to the first character of
160  each substring and the offset to the first character after the end of each  each substring and the offset to the first character after the end of each
161  substring, respectively. The 0th element of the vector relates to the entire  substring, respectively. The 0th element of the vector relates to the entire
162  portion of \fIstring\fR that was matched; subsequent elements relate to the  portion of \fIstring\fP that was matched; subsequent elements relate to the
163  capturing subpatterns of the regular expression. Unused entries in the array  capturing subpatterns of the regular expression. Unused entries in the array
164  have both structure members set to -1.  have both structure members set to -1.
165    .P
166  A successful match yields a zero return; various error codes are defined in the  A successful match yields a zero return; various error codes are defined in the
167  header file, of which REG_NOMATCH is the "expected" failure code.  header file, of which REG_NOMATCH is the "expected" failure code.
168    .
169    .
170  .SH ERROR MESSAGES  .SH "ERROR MESSAGES"
171  The \fBregerror()\fR function maps a non-zero errorcode from either  .rs
172  \fBregcomp\fR or \fBregexec\fR to a printable message. If \fIpreg\fR is not  .sp
173    The \fBregerror()\fP function maps a non-zero errorcode from either
174    \fBregcomp()\fP or \fBregexec()\fP to a printable message. If \fIpreg\fP is not
175  NULL, the error should have arisen from the use of that structure. A message  NULL, the error should have arisen from the use of that structure. A message
176  terminated by a binary zero is placed in \fIerrbuf\fR. The length of the  terminated by a binary zero is placed in \fIerrbuf\fP. The length of the
177  message, including the zero, is limited to \fIerrbuf_size\fR. The yield of the  message, including the zero, is limited to \fIerrbuf_size\fP. The yield of the
178  function is the size of buffer needed to hold the whole message.  function is the size of buffer needed to hold the whole message.
179    .
180    .
181  .SH STORAGE  .SH MEMORY USAGE
182    .rs
183    .sp
184  Compiling a regular expression causes memory to be allocated and associated  Compiling a regular expression causes memory to be allocated and associated
185  with the \fIpreg\fR structure. The function \fBregfree()\fR frees all such  with the \fIpreg\fP structure. The function \fBregfree()\fP frees all such
186  memory, after which \fIpreg\fR may no longer be used as a compiled expression.  memory, after which \fIpreg\fP may no longer be used as a compiled expression.
187    .
188    .
189  .SH AUTHOR  .SH AUTHOR
190    .rs
191    .sp
192  Philip Hazel <ph10@cam.ac.uk>  Philip Hazel <ph10@cam.ac.uk>
193  .br  .br
194  University Computing Service,  University Computing Service,
195  .br  .br
 New Museums Site,  
 .br  
196  Cambridge CB2 3QG, England.  Cambridge CB2 3QG, England.
197    .P
198    .in 0
199    Last updated: 07 September 2004
200  .br  .br
201  Phone: +44 1223 334714  Copyright (c) 1997-2004 University of Cambridge.
   
 Copyright (c) 1997-1999 University of Cambridge.  

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