/* http://stackoverflow.com/a/17195644/541686 */

#include <string.h>
#include <stdio.h>

int opterr = 1, /* if error message should be printed */
    optind = 1, /* index into parent argv vector */
    optopt,     /* character checked for validity */
    optreset;   /* reset getopt */
char *optarg;   /* argument associated with option */

#define BADCH (int) '?'
#define BADARG (int) ':'
#define EMSG ""

/*
* getopt --
*      Parse argc/argv argument vector.
*/
int getopt(int nargc, char *const nargv[], const char *ostr) {
  static char *place = EMSG; /* option letter processing */
  const char *oli;           /* option letter list index */

  if (optreset || !*place) { /* update scanning pointer */
    optreset = 0;
    if (optind >= nargc || *(place = nargv[optind]) != '-') {
      place = EMSG;
      return (-1);
    }
    if (place[1] && *++place == '-') { /* found "--" */
      ++optind;
      place = EMSG;
      return (-1);
    }
  } /* option letter okay? */
  if ((optopt = (int) *place++) == (int) ':' || !(oli = strchr(ostr, optopt))) {
    /*
    * if the user didn't specify '-' as an option,
    * assume it means -1.
    */
    if (optopt == (int) '-')
      return (-1);
    if (!*place)
      ++optind;
    if (opterr && *ostr != ':')
      (void) printf("illegal option -- %c\n", optopt);
    return (BADCH);
  }
  if (*++oli != ':') { /* don't need argument */
    optarg = NULL;
    if (!*place)
      ++optind;
  } else {      /* need an argument */
    if (*place) /* no white space */
      optarg = place;
    else if (nargc <= ++optind) { /* no arg */
      place = EMSG;
      if (*ostr == ':')
        return (BADARG);
      if (opterr)
        (void) printf("option requires an argument -- %c\n", optopt);
      return (BADCH);
    } else /* white space */
      optarg = nargv[optind];
    place = EMSG;
    ++optind;
  }
  return (optopt); /* dump back option letter */
}