regcomp, regexec, regerror, regfree — POSIX regex functions
#include <sys/types.h> #include <regex.h>
int
regcomp( |
regex_t *preg, |
| const char *regex, | |
int cflags); |
int
regexec( |
const regex_t *preg, |
| const char *string, | |
| size_t nmatch, | |
| regmatch_t pmatch[], | |
int eflags); |
size_t
regerror( |
int errcode, |
| const regex_t *preg, | |
| char *errbuf, | |
size_t errbuf_size); |
void
regfree( |
regex_t *preg); |
regcomp() is used to
compile a regular expression into a form that is suitable
for subsequent regexec()
searches.
regcomp() is supplied with
preg, a pointer to
a pattern buffer storage area; regex, a pointer to the
null-terminated string and cflags, flags used to
determine the type of compilation.
All regular expression searching must be done via a
compiled pattern buffer, thus regexec() must always be supplied with
the address of a regcomp()
initialized pattern buffer.
cflags may be
the bitwise-or of
one or more of the following:
REG_EXTENDEDUse POSIX Extended
Regular Expression syntax when interpreting
regex. If not
set, POSIX Basic
Regular Expression syntax is used.
REG_ICASEDo not differentiate case. Subsequent regexec() searches using this
pattern buffer will be case insensitive.
REG_NOSUBSupport for substring addressing of matches is not
required. The nmatch and pmatch arguments to
regexec() are ignored
if the pattern buffer supplied was compiled with this
flag set.
REG_NEWLINEMatch-any-character operators don't match a newline.
A nonmatching list ([^...]) not
containing a newline does not match a newline.
Match-beginning-of-line operator (^) matches the empty string
immediately after a newline, regardless of whether
eflags, the
execution flags of regexec(), contains REG_NOTBOL.
Match-end-of-line operator ($) matches the empty string
immediately before a newline, regardless of whether
eflags
contains REG_NOTEOL.
regexec() is used to match
a null-terminated string against the precompiled pattern
buffer, preg.
nmatch and
pmatch are used to
provide information regarding the location of any matches.
eflags may be the
bitwise-or of one or
both of REG_NOTBOL and
REG_NOTEOL which cause
changes in matching behavior described below.
REG_NOTBOLThe match-beginning-of-line operator always fails
to match (but see the compilation flag REG_NEWLINE above) This flag may be
used when different portions of a string are passed
to regexec() and the
beginning of the string should not be interpreted as
the beginning of the line.
REG_NOTEOLThe match-end-of-line operator always fails to
match (but see the compilation flag REG_NEWLINE above)
Unless REG_NOSUB was set
for the compilation of the pattern buffer, it is possible
to obtain substring match addressing information.
pmatch must be
dimensioned to have at least nmatch elements. These are
filled in by regexec() with
substring match addresses. Any unused structure elements
will contain the value −1.
The regmatch_t structure which
is the type of pmatch is defined in
<regex.h>
typedef struct { regoff_t rm_so;regoff_t rm_eo;} regmatch_t;
Each rm_so
element that is not −1 indicates the start offset of
the next largest substring match within the string. The
relative rm_eo
element indicates the end offset of the match, which is the
offset of the first character after the matching text.
regerror() is used to turn
the error codes that can be returned by both regcomp() and regexec() into error message strings.
regerror() is passed the
error code, errcode, the pattern buffer,
preg, a pointer to
a character string buffer, errbuf, and the size of the
string buffer, errbuf_size. It returns the
size of the errbuf
required to contain the null-terminated error message
string. If both errbuf and errbuf_size are nonzero,
errbuf is filled in
with the first errbuf_size
− 1 characters of the error message and a
terminating null byte ('\0').
regcomp() returns zero for a
successful compilation or an error code for failure.
regexec() returns zero for a
successful match or REG_NOMATCH
for failure.
The following errors can be returned by regcomp():
REG_BADBRInvalid use of back reference operator.
REG_BADPATInvalid use of pattern operators such as group or list.
REG_BADRPTInvalid use of repetition operators such as using '*' as the first character.
REG_EBRACEUn-matched brace interval operators.
REG_EBRACKUn-matched bracket list operators.
REG_ECOLLATEInvalid collating element.
REG_ECTYPEUnknown character class name.
REG_EENDNon specific error. This is not defined by POSIX.2.
REG_EESCAPETrailing backslash.
REG_EPARENUn-matched parenthesis group operators.
REG_ERANGEInvalid use of the range operator, e.g., the ending point of the range occurs prior to the starting point.
REG_ESIZECompiled regular expression requires a pattern buffer larger than 64Kb. This is not defined by POSIX.2.
REG_ESPACEThe regex routines ran out of memory.
REG_ESUBREGInvalid back reference to a subexpression.
This page is part of release 3.35 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at http://man7.org/linux/man-pages/.
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Copyright (C), 1995, Graeme W. Wilford. (Wilf.) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. Wed Jun 14 16:10:28 BST 1995 Wilf. (G.Wilfordee.surrey.ac.uk) Tiny change in formatting - aeb, 950812 Modified 8 May 1998 by Joseph S. Myers (jsm28cam.ac.uk) show the synopsis section nicely |