Function exchange

resources/fegetopt.c:243–268

#endif

static void exchange (char **argv)
{
  char *temp, **first, **last;

  /* Reverse all the elements [first_nonopt, fe_optind) */
  first = &argv[first_nonopt];
  last  = &argv[fe_optind-1];
  while (first < last) {
    temp = *first; *first = *last; *last = temp; first++; last--;
  }
  /* Put back the options in order */
  first = &argv[first_nonopt];
  first_nonopt += (fe_optind - last_nonopt);
  last  = &argv[first_nonopt - 1];
  while (first < last) {
    temp = *first; *first = *last; *last = temp; first++; last--;
  }

  /* Put back the non options in order */
  first = &argv[first_nonopt];
  last_nonopt = fe_optind;
  last  = &argv[last_nonopt-1];
  while (first < last) {
    temp = *first; *first = *last; *last = temp; first++; last--;
  }
}

/* Scan elements of ARGV (whose length is ARGC) for option characters
   given in OPTSTRING.