Using getopt in C with non-option arguments

Question

I'm making a small program in C that deals with a lot of command line arguments, so I decided to use getopt to sort them for me.

However, I want two non-option arguments (source and destination files) to be mandatory, so you have to have them as arguments while calling the program, even if there's no flags or other arguments.

Here's a simplified version of what I have to handle the arguments with flags:

while ((c = getopt(argc, argv, "i:d:btw:h:s:")) != -1) {
    switch (c) {
        case 'i': {
            i = (int)atol(optarg);
        }
        case 'd': {
            d = (int)atol(optarg);
        }
        case 'b':
            buf = 1;
            break;
        case 't':
            time = 1;
            break;
        case 'w':
            w = (int)atol(optarg);
            break;
        case 'h':
            h = (int)atol(optarg);
            break;
        case 's':
            s = (int)atol(optarg);
            break;
        default:
            break;
    }
}

How do I edit this so that non-option arguments are also handled?

I also want to be able to have the non-options either before or after the options, so how would that be handled?

Answer 1

getopt sets the optind variable to indicate the position of the next argument.

Add code similar to this after the options loop:

if (argv[optind] == NULL || argv[optind + 1] == NULL) {
  printf("Mandatory argument(s) missing\n");
  exit(1);
}

Edit:

If you want to allow options after regular arguments you can do something similar to this:

while (optind < argc) {
  if ((c = getopt(argc, argv, "i:d:btw:h:s:")) != -1) {
    // Option argument
    switch (c) {
        case 'i': {
            i = (int)atol(optarg);
        }
        case 'd': {
            d = (int)atol(optarg);
        }
        case 'b':
            buf = 1;
            break;
        case 't':
            time = 1;
            break;
        case 'w':
            w = (int)atol(optarg);
            break;
        case 'h':
            h = (int)atol(optarg);
            break;
        case 's':
            s = (int)atol(optarg);
            break;
        default:
            break;
    }
    else {
        // Regular argument
        <code to handle the argument>
        optind++;  // Skip to the next argument
    }
}

Answer 2

Really good example could be found here: GNU Libc The code:

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main (int argc, char **argv)
{
int aflag = 0;
int bflag = 0;
char *cvalue = NULL;
int index;
int c;

opterr = 0;

while ((c = getopt (argc, argv, "abc:")) != -1)
switch (c)
{
case 'a':
    aflag = 1;
    break;
case 'b':
    bflag = 1;
    break;
case 'c':
    cvalue = optarg;
    break;
case '?':
    if (optopt == 'c')
    fprintf (stderr, "Option -%c requires an argument.\n", optopt);
    else if (isprint (optopt))
    fprintf (stderr, "Unknown option `-%c'.\n", optopt);
    else
    fprintf (stderr,
        "Unknown option character `\\x%x'.\n",
        optopt);
    return 1;
default:
    abort ();
}

printf ("aflag = %d, bflag = %d, cvalue = %s\n",
    aflag, bflag, cvalue);

for (index = optind; index < argc; index++)
printf ("Non-option argument %s\n", argv[index]);
return 0;
}

It allows to have options before and after arguments. I did compile and run test example:

$ ./a.out aa ff bb -a -ctestparam hello
aflag = 1, bflag = 0, cvalue = testparam
Non-option argument aa
Non-option argument ff
Non-option argument bb
Non-option argument hello

Answer 3

The GNU Libc example is also not working for MinGW-W64 7.1.0. The non-option arguments are not shifted to the end so that the parsing stops after the first non-option arguments.

So the default permutation option seems not to work.