regex.h(7POSIX)

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

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
    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.

APPLICATION USAGE
None.

RATIONALE
None.

FUTURE DIRECTIONS
None.

SEE ALSO
<sys_types.h>

The System Interfaces volume of POSIX.1-2017, regcomp()

COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .