How do I use getopt_long to parse multiple arguments?

Question

#include <iostream>
#include <getopt.h>

#define no_argument 0
#define required_argument 1 
#define optional_argument 2


int main(int argc, char * argv[])
{
  std::cout << "Hello" << std::endl;

  const struct option longopts[] =
  {
    {"version",   no_argument,        0, 'v'},
    {"help",      no_argument,        0, 'h'},
    {"stuff",     required_argument,  0, 's'},
    {0,0,0,0},
  };

  int index;
  int iarg=0;

  //turn off getopt error message
  opterr=1; 

  while(iarg != -1)
  {
    iarg = getopt_long(argc, argv, "s:vh", longopts, &index);

    switch (iarg)
    {
      case 'h':
        std::cout << "You hit help" << std::endl;
        break;

      case 'v':
        std::cout << "You hit version" << std::endl;
        break;

      case 's':
        std::cout << "You hit stuff" << std::endl;

        if(optarg)
          std::cout << "Your argument(s): " << optarg << std::endl;

        break;
    }
  }

  std::cout << "GoodBye!" << std::endl;

  return 0; 
}

Desired output:

./a.out --stuff someArg1 someArg2

Hello
You hit stuff
Your agument(s): someArg1 someArg2
GoodBye!

Herron

it only captures 1 argument: actual output Hello You hit stuff Your argument(s): someArg1 GoodBye! – Herron

Answer 1

getopt returns -1 when all option args have been processed. The --stuff is recognized as an option that takes an argument, in this case someArg1. The someArg2 arg does not start with - or --, so it is not an option. By default, this will be permuted to the end of argv. After getopt returns -1, all non-option args will be in argv from optind to argc-1:

while (iarg != -1) {
    iarg = getopt_long(argc, argv, "s:vh", longopts, &index);
    // ...
}

for (int i = optind; i < argc; i++) {
    cout << "non-option arg: " << argv[i] << std::endl;
}

If you add a single - to the start of optstring, getopt will return 1 (not '1') and point optarg to the non-option parameter:

while (iarg != -1) {
    iarg = getopt_long(argc, argv, "-s:vh", longopts, &index);

    switch (iarg)
    {
      // ...
      case 1:
        std::cout << "You hit a non-option arg:" << optarg << std::endl;
        break;
    }
}

Autogiro

Answer 2

In the line ./a.out --stuff someArg1 someArg2 the shell interprets three arguments to a.out. You want the shell to interpret "someArg1 someArg2" as one argument - so put the words in quotes:

./a.out --stuff "someArg1 someArg2"

Alyssa

Answer 3

optarg points to "someArg1" and argv[optind] is "someArg2" if it exists and is not an option. You can simply use it and then consume it by incrementing optind.

case 's':
    std::cout << "You hit stuff" << std::endl;

    if (optind < argc && argv[optind][0] != '-') {
       std::cout << "Your argument(s): " << optarg << argv[optind] << std::endl;
       optind++;
    } else {
        printusage();
    }
    break;

Note this can work for an arbitrary number of arguments:

case 's':
    std::cout << "You hit stuff." << std::endl;
    std::cout << "Your arguments:" std::endl << optarg << std::endl;

    while (optind < argc && argv[optind][0] != '-') {
       std::cout << argv[optind] << std::endl;
       optind++;
    } 
    break;

c++ getopt-long command-line-arguments

Sarcomatosis

you should specify tags – Hedy

Answer 4

I'm working on windows, so I had to compile getopt and getopt_long from this excellent source

I modified getopt_long.c (below) to accommodate two input arguments. I didn't bother with the more general case of multiple arguments since that would require more (and cleaner) rework than I had time/need for. The second argument is placed in another global, "optarg2".

If you don't need to compile getopt from source, Frank's answer above is more elegant.

extern char * optarg2
.
.
.
int getopt_long(nargc, nargv, options, long_options, index) 
{
.
.
.
if (long_options[match].has_arg == required_argument ||
            long_options[match].has_arg == optional_argument ||
            long_options[match].has_arg == two_req_arguments) {
            if (has_equal)
                optarg = has_equal;
            else
                optarg = nargv[optind++];
            if (long_options[match].has_arg == two_req_arguments) {
                optarg2 = nargv[optind++];
            }
        }
        if ((long_options[match].has_arg == required_argument ||
             long_options[match].has_arg == two_req_arguments)
            && (optarg == NULL)) {
            /*
             * Missing argument, leading :
             * indicates no error should be generated
             */
            if ((opterr) && (*options != ':'))
                (void)fprintf(stderr,
                  "%s: option requires an argument -- %s\n",
                  __progname(nargv[0]), current_argv);
            return (BADARG);
        }
        if ((long_options[match].has_arg == two_req_arguments)
            && (optarg2 == NULL)) {
            /*
             * Missing 2nd argument, leading :
             * indicates no error should be generated
             */
            if ((opterr) && (*options != ':'))
                (void)fprintf(stderr,
                  "%s: option requires 2nd argument -- %s\n",
                  __progname(nargv[0]), current_argv);
            return (BADARG);
        }

You'll also need to add a define in getopt.h for "two_required_args" or "multiple_args" as you see fit.

edit: I'm bad at markdown

Wolpert