API of regcomp

regcomp.c

int regcomp(regex_t *preg, const char *regex, int cflags);

preg - It is a pointer to a structure regex_t.

regex - Pointer to a null terminated string which contains the pattern

cflags - bitwise-or of one or more of the following:

       REG_EXTENDED
              Use POSIX Extended Regular Expression syntax when interpreting regex.  If not set, POSIX Basic Regular Expression syntax is used.
       REG_ICASE
              Do not differentiate case.  Subsequent regexec() searches using this pattern buffer will be case insensitive.
       REG_NOSUB
              Support for substring addressing of matches is not required.  The nmatch and pmatch arguments to regexec() are ignored if the pattern buffer supplied was  compiled  with  this flag set.
       REG_NEWLINE
              Match-any-character operators don't match a newline.
              A nonmatching list ([^...])  not containing a newline does not match a newline.
              Match-beginning-of-line operator (^) matches the empty string immediately after a newline, regardless of whether eflags, the execution flags of regexec(), contains REG_NOTBOL.
              Match-end-of-line operator ($) matches the empty string immediately before a newline, regardless of whether eflags contains REG_NOTEOL.

regexecute.c

void