Parsing '?' in getopt

Question

void display(char * str){
   printf(\"%s: Missing file\\n\", str);
}

int main(int argc, char **argv)
{

    int longIndex, opt = 0;
    const char *optString = \"h?         


        

Answer 1

The question mark '?' is returned by getopt when it finds an argument that's not in the optstring or if it detects a missing option argument, so you shouldn't use '?' in optstring because it's sort of reserved for that, instead you should use the more conventional 'h' for help.

See the man page

Edit: This is an example:

switch (opt) {
    case 'n':
        some_flag = 1;
        break;
    case 'h': /* help */
    default: /* '?' unknown opt or missing arg*/
        fprintf(stderr, "Usage: %s [-n nsecs] \n", argv[0]);
        exit(EXIT_FAILURE);
}

Answer 2

const char *optString = "h?";

Above line replace with following line

const char *optString = "h\?";

this is the literal of question mark in C language

Answer 3

If you include -? with --help on your help message, leave the question mark out of your call to getopt, leave it out of the case option, and make sure that --help is the first case option in your list, the question mark works as you'd want it to.