break; case OPT_PREFIX: output_prefix = arg;
parse_opt (int key, char *arg, struct argp_state *state){  switch (key)    {    case OPT_QUIET:      be_quiet = 1;      break;    case OPT_POSIX:      posix_conformance = 1;      break;    case OPT_OLDSTYLE:      oldstyle_tables = 1;      break;    case 'c':      force_output = 1;      break;    case 'f':      charmap_file = arg;      break;    case 'i':      input_file = arg;      break;    case 'u':      repertoire_global = arg;      break;    case 'v':      verbose = 1;      break;    default:      return ARGP_ERR_UNKNOWN;    }  return 0;}