CODEWITHSUNDEEP
c++getoptgetopt-long
R71
R71

Reputation: 4523

getopt_long not printing error message

I am using getopt and getopt_long to parse the arguments of a c++ program. When the arguments are given correctly, I dont have a problem. Also, when wrong short arguments are given, the error message is printed correctly. But when a wrong long argument is given, I am not getting its error message.

Here is the code:

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

static struct option long_options[] = {
    {"aa", no_argument,  0,  'a' },
    {"bb", no_argument,  0,  'b' },
    {0,    0,            0,  0 }
};

int main (int argc, char **argv)
{
  int c;
  int option_index;

    opterr = 0;
    while ((c = getopt_long (argc, argv, "ab",
                    long_options, &option_index)) != -1)
        switch (c) {
            case 0:
                printf ("option %s", long_options[option_index].name);
                if (optarg)
                    printf (" with arg %s", optarg);
                printf ("\n");
                break;
            case 'a':
                printf("got option a\n");
                break;
            case 'b':
                printf("got option b\n");
                break;
            case '?':
                if (isprint (optopt))
                    printf ("Unknown option `-%c'.\n", optopt);
                else
                    printf ("Unknown option character `\\x%x'.\n", optopt);
                return 1;
            default:
                printf("?? getopt_long returned character code 0%o ??\n", c);
                return 1;
        }
    if (optind < argc) {
        printf("non-option ARGV-elements: ");
        while (optind < argc)
            printf("%s ", argv[optind++]);
        printf("\n");
    }
    return 0;
}

Here are the runs:

$ ./a.exe -ab --aa --bb # works correctly
    got option a
    got option b
    got option a
    got option b
$ ./a.exe -z      # prints error message correctly
    Unknown option `-z'.
$ ./a.exe --zz    # not getting the error message for "--zz"
    Unknown option character `\x0'.

How to print error message that --zz is an unknown option?

Upvotes: 1

Views: 1173

Answers (1)

Galik
Galik

Reputation: 48615

In this case I have used the fact that optind has just been incremented after pointing to the failed option to discover the option from the original argv.

So I would do something like this:

case '?':
    std::cerr << "Unknown option " << argv[optind - 1] << ".\n";
    return EXIT_FAILURE;

There is no need to differentiate between long and short options this way.

Upvotes: 0

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