REGEX(3) | Linux Programmer's Manual | REGEX(3) |
NAME
regcomp, regexec, regerror, regfree - POSIX regex functionsSYNOPSIS
#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);
DESCRIPTION
POSIX regex compiling
regcomp() is used to compile a regular expression into a form that is suitable for subsequent regexec() searches.- REG_EXTENDED
- Use POSIX Extended Regular Expression syntax when interpreting regex. If not set, POSIX Basic Regular Expression syntax is used.
- REG_ICASE
- Do not differentiate case. Subsequent regexec() searches using this pattern buffer will be case insensitive.
- REG_NOSUB
- Do not report position of matches. The nmatch and pmatch arguments to regexec() are ignored if the pattern buffer supplied was compiled with this flag set.
- REG_NEWLINE
-
Match-any-character operators don't match a newline.
POSIX regex matching
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_NOTBOL
- The 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_NOTEOL
- The match-end-of-line operator always fails to match (but see the compilation flag REG_NEWLINE above)
Byte offsets
Unless REG_NOSUB was set for the compilation of the pattern buffer, it is possible to obtain match addressing information. pmatch must be dimensioned to have at least nmatch elements. These are filled in by regexec() with substring match addresses. The offsets of the subexpression starting at the ith open parenthesis are stored in pmatch[i]. The entire regular expression's match addresses are stored in pmatch[0]. (Note that to return the offsets of N subexpression matches, nmatch must be at least N+1.) Any unused structure elements will contain the value -1.typedef struct {
regoff_t rm_so;
regoff_t rm_eo;
} regmatch_t;
POSIX error reporting
regerror() is used to turn the error codes that can be returned by both regcomp() and regexec() into error message strings.POSIX pattern buffer freeing
Supplying regfree() with a precompiled pattern buffer, preg will free the memory allocated to the pattern buffer by the compiling process, regcomp().RETURN VALUE
regcomp() returns zero for a successful compilation or an error code for failure.ERRORS
The following errors can be returned by regcomp():- REG_BADBR
- Invalid use of back reference operator.
- REG_BADPAT
- Invalid use of pattern operators such as group or list.
- REG_BADRPT
- Invalid use of repetition operators such as using '*' as the first character.
- REG_EBRACE
- Un-matched brace interval operators.
- REG_EBRACK
- Un-matched bracket list operators.
- REG_ECOLLATE
- Invalid collating element.
- REG_ECTYPE
- Unknown character class name.
- REG_EEND
- Nonspecific error. This is not defined by POSIX.2.
- REG_EESCAPE
- Trailing backslash.
- REG_EPAREN
- Un-matched parenthesis group operators.
- REG_ERANGE
- Invalid use of the range operator, e.g., the ending point of the range occurs prior to the starting point.
- REG_ESIZE
- Compiled regular expression requires a pattern buffer larger than 64Kb. This is not defined by POSIX.2.
- REG_ESPACE
- The regex routines ran out of memory.
- REG_ESUBREG
- Invalid back reference to a subexpression.
CONFORMING TO
POSIX.1-2001.SEE ALSO
grep(1), regex(7)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2013-02-11 | GNU |