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     } }