C - Access command-line arguments using getopt_long
===================================================

Public domain
********************************************************************************
    
    #include <getopt.h>
    #include <stdio.h>
    #include <stdlib.h>
    
    int main (int argc, char* argv[])
    {
            int next_option,i;
     
            /* "ho:v" short options means there is -h, -o (with an atgument) 
               and -v options */
            const char* const short_options = "ho:v";
    
            /* An array describing valid long options. */
            const struct option long_options[] = {
                    { "help",    0, NULL, 'h' },
                    { "output",  1, NULL, 'o' },
                    { "verbose", 0, NULL, 'v' },
                    { NULL,       0, NULL, 0   }   /* Required at end of array.  */
            };
     
            /* Whether to display verbose messages.   */ 
            int verbose = 0; 
     
    
            do {
                    next_option = getopt_long (argc, argv, short_options,
                                                     long_options, NULL); 
                    switch (next_option)
                    {
                    case 'h':
                            fprintf (stdout, "-h or --help found: " 
                                             "Here goes your help ...\n");
                            break; 
     
                    case 'o':
                            fprintf (stdout, "-o or --ouput found: " 
                                             "Argument is : %s\n",optarg);
                            break; 
     
                    case 'v':
                            fprintf (stdout, "-v or  --verbose found: "
                                             "Verbose flag will be set\n",optarg);
                            break; 
     
                    case '?':
                            fprintf (stdout, "Invalid option found !!!\n");
                            break; 
                    case -1:
                            fprintf (stdout, "End of option list reached.\n");
                            break; 
     
                    default:
                            fprintf (stdout, "getopt_long returned unexpected value.\n");
                            abort ();
                    }
            }
            while (next_option != -1);
     
            fprintf (stdout, "non-option argument goes here if exist: \n");
            for (i = optind; i < argc; ++i)
                        printf ("Argument: %s\n", argv[i]); 
     
            return 0; 
    }

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### Output

    $ ./a.out -o abc.txt -h -v "test ing" additional "argu ments"
    -o or --ouput found: Argument is : abc.txt
    -h or --help found: Here goes your help ...
    -v or  --verbose found: Verbose flag will be set
    End of option list reached.
    non-option argument goes here if exist: 
    Argument: test ing
    Argument: additional
    Argument: argu ments

********************************************************************************
_BY: Pejman Moghadam_  
_TAG: c, getopt_  
_DATE: 2011-05-28 23:38:24_