regex.h man page

Prolog

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regex.h — regular expression matching types

Synopsis

#include <regex.h>

Description

The <regex.h> header shall define the structures and symbolic constants used by the regcomp(), regexec(), regerror(), and regfree() functions.

The <regex.h> header shall define the regex_t structure type, which shall include at least the following member:

size_t    re_nsub    Number of parenthesized subexpressions.

The <regex.h> header shall define the size_t type as described in <sys/types.h>.

The <regex.h> header shall define the regoff_t type as a signed integer type that can hold the largest value that can be stored in either a ptrdiff_t type or a ssize_t type.

The <regex.h> header shall define the regmatch_t structure type, which shall include at least the following members:

regoff_t    rm_so    Byte offset from start of string
                     to start of substring.
regoff_t    rm_eo    Byte offset from start of string of the
                     first character after the end of substring.

The <regex.h> header shall define the following symbolic constants for the cflags parameter to the regcomp() function:

REG_EXTENDED
Use Extended Regular Expressions.
REG_ICASE
Ignore case in match.
REG_NOSUB
Report only success or fail in regexec().
REG_NEWLINE
Change the handling of <newline>.

The <regex.h> header shall define the following symbolic constants for the eflags parameter to the regexec() function:

REG_NOTBOL
The <circumflex> character ('^'), when taken as a special character, does not match the beginning of string.
REG_NOTEOL
The <dollar-sign> ('$'), when taken as a special character, does not match the end of string.

The <regex.h> header shall define the following symbolic constants as error return values:

REG_NOMATCH
regexec() failed to match.
REG_BADPAT
Invalid regular expression.
REG_ECOLLATE
Invalid collating element referenced.
REG_ECTYPE
Invalid character class type referenced.
REG_EESCAPE
Trailing <backslash> character in pattern.
REG_ESUBREG
Number in \digit invalid or in error.
REG_EBRACK
"[]" imbalance.
REG_EPAREN
"\(\)" or "()" imbalance.
REG_EBRACE
"\{\}" imbalance.
REG_BADBR
Content of "\{\}" invalid: not a number, number too large, more than two numbers, first larger than second.
REG_ERANGE
Invalid endpoint in range expression.
REG_ESPACE
Out of memory.
REG_BADRPT
'?', '*', or '+' not preceded by valid regular expression.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

int    regcomp(regex_t *restrict, const char *restrict, int);
size_t regerror(int, const regex_t *restrict, char *restrict, size_t);
int    regexec(const regex_t *restrict, const char *restrict, size_t,
           regmatch_t [restrict], int);
void   regfree(regex_t *);

The implementation may define additional macros or constants using names beginning with REG_.

The following sections are informative.

See Also

<sys_types.h>

The System Interfaces volume of POSIX.1‐2008, regcomp()

Info

2013 IEEE/The Open Group POSIX Programmer's Manual