c - getopt does not parse optional arguments to parameters

Question

In C, getopt_long does not parse the optional arguments to command line parameters parameters.

When I run the program, the optional argument is not recognized like the example run below.

$ ./respond --praise John
Kudos to John
$ ./respond --blame John
You suck !
$ ./respond --blame
You suck !

Here is the test code.

#include <stdio.h>
#include <getopt.h>

int main(int argc, char ** argv )
{
    int getopt_ret, option_index;
    static struct option long_options[] = {
               {"praise",  required_argument, 0, 'p'},
               {"blame",  optional_argument, 0, 'b'},
               {0, 0, 0, 0}       };
    while (1) {
        getopt_ret = getopt_long( argc, argv, "p:b::",
                                  long_options,  &option_index);
        if (getopt_ret == -1) break;

        switch(getopt_ret)
        {
            case 0: break;
            case 'p':
                printf("Kudos to %s
", optarg); break;
            case 'b':
                printf("You suck ");
                if (optarg)
                    printf (", %s!
", optarg);
                else
                    printf ("!
", optarg);
                break;
            case '?':
                printf("Unknown option
"); break;
        }
    } 
    return 0;
}

Answer 1

Although not mentioned in glibc documentation or getopt man page, optional arguments to long style command line parameters require 'equals sign' (=). Space separating the optional argument from the parameter does not work.

An example run with the test code:

$ ./respond --praise John
Kudos to John
$ ./respond --praise=John
Kudos to John
$ ./respond --blame John
You suck !
$ ./respond --blame=John
You suck , John!