NAME

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

Perform pattern matching in a case-insensitive manner.

REG_MINIMAL

Change default matching behavior to leftmost shortest possible match. Only applicable to REG_EXTENDED regular expressions.

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_.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

<sys/types.h>

XSH regcomp

CHANGE HISTORY

First released in Issue 4.

Originally derived from the ISO POSIX-2 standard.

Issue 6

The REG_ENOSYS constant is marked obsolescent.

The restrict keyword is added to the prototypes for regcomp(), regerror(), and regexec().

A statement is added that the size_t type is defined as described in <sys/types.h>.

Issue 7

SD5-XBD-ERN-60 is applied.

The obsolescent REG_ENOSYS constant is removed.

This reference page is clarified with respect to macros and symbolic constants.

Issue 8

Austin Group Defect 793 is applied, adding REG_MINIMAL.

Austin Group Defect 1031 is applied, changing the description of REG_ICASE.