getopt.c

/* -*- mode: c; tab-width: 4; c-basic-offset: 3; c-file-style: "linux" -*- */
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "getopt.h"

int     opterr = 1;      // if error message should be printed
int     optind = 1;      // index into parent argv vector
int     optopt;          // character checked for validity
int     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
   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 != ':')
         fprintf(stderr, "%s: illegal option -- %c\n", nargv[0], 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)
         {
            fprintf(stderr, "%s: option requires an argument -- %c\n",
               nargv[0], optopt);
         }
         return BADCH;
      }
      else // white space
         optarg = nargv[optind];
      place = EMSG;
      ++optind;
   }

   return optopt; // dump back option letter
}