POSIX regex option not working

Question

I use | for alternatives, but it does not work. Am I doing something wrong?

Thanks!

The following code always returns No match :

 #include <sys/types.h> #include <regex.h> #include <stdio.h> #include <stdlib.h> #include <sys/types.h> int main(int argc, char *argv[]){ regex_t regex; int reti; char msgbuf[100]; /* Compile regular expression */ reti = regcomp(&regex, "ab(c|d)", 0); if( reti ){ fprintf(stderr, "Could not compile regex\n"); exit(1); } /* Execute regular expression */ reti = regexec(&regex, "abd", 0, NULL, 0); if( !reti ){ puts("Match"); } else if( reti == REG_NOMATCH ){ puts("No match"); } else{ regerror(reti, &regex, msgbuf, sizeof(msgbuf)); fprintf(stderr, "Regex match failed: %s\n", msgbuf); exit(1); } /* Free compiled regular expression if you want to use the regex_t again */ regfree(&regex); return 0; } 

Answer 1

As the POSIX manual reports, you need to set the flags argument to enable extended regular expressions.

  REG_EXTENDED Use POSIX Extended Regular Expression syntax when interpreting regex. If not set, POSIX Basic Regular Expression syntax is used.