parse_opt
ret = parse_opt(opt, ap, data, f, &outargs);
ret = parse_opt(opt, arg, data, f, &outargs);
ret = parse_opt(opt, tofree, data, f, &outargs);
int parse_opt(char *, struct opt_t *);
if (parse_opt(*argv, &opt))
if (parse_opt(*argv, &opt)) {