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.
