// ------- getopt_test.c beg ---------

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

// Ref.:
// Alp-ch02-writing-good-gnu-linux-software.pdf
// Libc_25.html#SEC531
//
// Compile it:
// gcc -Wall getopt_test.c -o getopt_test
// 
// Run it:
// getopt_test -h
// getopt_test --help

void print_usage(char *program);

// This becomes true ('v') if --verbose or -v option was seen.
int verbose_flag = 0;

// Optional value after -v or --verbose=.
int verbose_level= 0;

const struct option long_options[] = {
 {"verbose",   optional_argument, &verbose_flag, 'v'},
 {"help",      no_argument,       NULL, 'h'},
 {"user",      required_argument, NULL, 'u'},
 {"password",  required_argument, NULL, 'p'},
 {NULL,        0,                 NULL,  0 }
};

// u and p take values and v can optionally have a value.
static const char *short_options = "v:hu:p:";

int main(int argc, char *argv[])
{
 int c;
 int option_index = 0;  // Valid only for long_options (eg. --help).

while ((c = getopt_long(argc, argv, short_options, long_options,
        &option_index)) != -1)
 {
   switch (c)
   {
        case  0:   // --verbose
           if (long_options[option_index].val == 'v')
           {
             ;
           }
           if (optarg)
             verbose_level = atoi(optarg);

           break;


        case 'v':   // -v
           verbose_flag = 'v';  // This is not set automatically.
           if (optarg)
             verbose_level = atoi(optarg);
           break;


       case 'h':  //  -h or --help
           printf("Help is here\n");
           print_usage(argv[0]);
           break;


       case 'u':  // -u or --user
           printf("User is %s\n",  optarg);
           break;


       case 'p':  // -p or --password
           printf("Password is %s\n", optarg);
           break;


       case '?': // Invalid argument
           print_usage(argv[0]), exit(-1);
           break;


       default:
           printf("Something went wrong.\n");
    }
 }

 printf("Verbose_flag was set? %s. level %d\n",(verbose_flag == 'v' ? "Yes" : "No"),
         verbose_level);

 // Print rest of the arguments not caught by getopt_long().
 if (optind < argc)
 {
   printf ("\nOther command line args:\n");
   while (optind < argc)  printf ("%s\n", argv[optind++]);
 }

 // Ok
 return 0;
}

void print_usage(char *program)
{
   fprintf(stderr, "Usage: %s [options]\n%s\n%s\n%s\n%s\n", program,
           "-h or --help",
           "-v [optional level] or --verbose [=optional level]",
           "-u <username>  or --user=<username>",
           "-p <password>  or --password=<password>");
}

// ------- getopt_test.c end ---------