Using getopt in C with non-option arguments

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?

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);
      break;
    case 'd':
      d = (int)atol(optarg);
      break;
    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:
      // bad or unknown option
      show_help();
      exit(1);
      break;
    }
  } else {
      // Regular argument
      <code to handle the argument>
      optind++;  // Skip to the next argument
  }
}