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 .