I always write my usage printing routine to take a FILE pointer, similar to the following, static void usage(const char *arg0, FILE *fp); and then at the ve

I always write my usage printing routine to take a FILE pointer, similar to the following, static void usage(const char *arg0, FILE *fp); and then at the very end of main's getopt switch something like, case 'h': usage(argv[0], stdout); return 0; default: usage(argv[0], stderr); return EXIT_FAILURE; } By default getopt prints (to stderr) a one line message for unknown options or missing arguments, so I usually don't bother catching ':' or '?' explicitly.