
//getopt.cÎÄ¼þ´úÂë£º
/* got this off net.sources */
#include <stdio.h>
#include <string.h>
#include "getopt.h"

/*
 * get option letter from argument vector
 */
int
 opterr = 1,  // should error messages be printed?
 optind = 1,  // index into parent argv vector
 optopt;   // character checked for validity
char *optarg;  // argument associated with option

#define EMSG ""
char *progname;   // may also be defined elsewhere

static void error(char *pch)
{
 if (!opterr) {
  return;  // without printing
 }
 fprintf(stderr, "%s: %s: %c\n",
  (NULL != progname) ? progname : "getopt", pch, optopt);
}

int getopt(int argc, char **argv, char *ostr)
{
 static char *place = EMSG; /* option letter processing */
 register char *oli;   /* option letter list index */
 if (!*place) {
  // update scanning pointer
  if (optind >= argc || *(place = argv[optind]) != '-' || !*++place) {
   return EOF; 
  }
  if (*place == '-') {
   // found "--"
   ++optind;
   return EOF;
  }
 }
 /* option letter okay? */
 if ((optopt = (int)*place++) == (int)':'
  || !(oli = strchr(ostr, optopt))) {
  if (!*place) {
   ++optind;
  }
  error("illegal option");
  return BADCH;
 }
 if (*++oli != ':') { 
  /* don't need argument */
  optarg = NULL;
  if (!*place)
   ++optind;
 } else {
  /* need an argument */
  if (*place) {
   optarg = place;  /* no white space */
  } else  if (argc <= ++optind) {
   /* no arg */
   place = EMSG;
   error("option requires an argument");
   return BADCH;
  } else {
   optarg = argv[optind];  /* white space */
  }
  place = EMSG;
  ++optind;
 }
 return optopt;   // return option letter
}
