Finally I got, my own get_opts function =D

30 Nov 2009 I spent some good hours trying to get this working...
After a hundreds of attemps I decide to make a real
algorithm.. and then .. after a little setting in the logic
I got really working as I expect..

Here is

#include <stdio.h>

static int   Optindx = 1;
static char *Optarg  = NULL;

short int
chstr (char ch, char *str)
{
 for (; *str; str++)
  if (ch == *str)
   return 0;
 return -1;
}

char *
search_arg(char **argv)
{
 char *ptr;
 if (argv[Optindx+1] == NULL)
  return 0;
 while (*(ptr = argv[++Optindx]) != '-')
  if (argv[Optindx] = NULL)
   return 0;
 
 return ptr;
}

int
get_opts(char **argv, char *legal)
{
 int letter = 0;

 if (Optarg == NULL)
  if (*(Optarg = argv[Optindx]) != '-')
   if ((Optarg = search_arg (argv)) == 0)
    return -1;
  
 if (*Optarg == '\0')
  if ((Optarg = search_arg (argv)) == 0)
   return -1;

 if (*(Optarg+1) == '-') {
  return -1;
 Optarg++;
 return 0;
 }


 if (chstr (*Optarg, legal) == 0)
  return letter = *Optarg++;
 else 
  return '?';
}

/* to Test */
int
main (int argc, char *argv[])
{
 int ch;


 if (argc < 2)
  return -1;

 while ((ch = get_opts(argv, "abc")) != -1) {
  switch (ch) {
   case 'a':
    putchar ('a');
    break;
   case 'b':
    putchar ('b');
    break;
   case 'c':
    putchar ('c');
    break;
   case '?':
    fprintf (stderr, "Unknown argument %c\n", *Optarg);
    return -1;
  }
 }
 putchar ('\n');
 return 0;
}

It parses 1char arguments, that can be passed in any order.
The switch -- forces to stop the parser

To program point of view, an argument is a character that
belongs to a string prefixed with a '-'