parsing command-line arguments with boost.program_options - C++

Question

I'm trying to parse command line arguments with boost. Here's my code (I am only including the part I need help with):

#include <iostream>
#include <iterator>
#include <boost/program_options.hpp>

using std::cerr;
using std::cout;
using std::endl;
namespace po = boost::program_options;

try {

    po::options_description desc("Allowed options");
    desc.add_options()
        ("help", "produce help message")
        ("compression", po::value<double>(), "set compression level");

    po::variables_map vm;
    po::store(po::parse_command_line(ac, av, desc), vm);
    po::notify(vm);

    if (vm.count("help")) {
        cout << desc << "\n";
        return 0;
      }

    if (vm.count("compression")) {
        cout << "Compression level was set to "
             << vm["compression"].as<double>() << ".\n";
      } else {
            cout << "Compression level was not set.\n";
            }
      }
    catch(exception& e) {
        cerr << "error: " << e.what() << "\n";
        return 1;
    }
    catch(...) {
        cerr << "Exception of unknown type!\n";
    }

I have my main function set to:

main(int argc, char const *argv[])

but, the code I was following https://github.com/boostorg/program_options/blob/develop/example/first.cpp contained these parameters:

int main(int ac, char* av[])

When I comile it, it spits out this and I am completely lost:

Terminal return

Answer 1

You also forgot to include exception - here is your code working..

#include <iostream>
#include <iterator>
#include <boost/program_options.hpp>
#include <exception>

using std::cerr;
using std::cout;
using std::endl;
using std::exception;
namespace po = boost::program_options;

int main(int ac, char** av){

try {

    po::options_description desc("Allowed options");
    desc.add_options()
        ("help", "produce help message")
        ("compression", po::value<double>(), "set compression level");

    po::variables_map vm;
    po::store(po::parse_command_line(ac, av, desc), vm);
    po::notify(vm);

    if (vm.count("help")) {
        cout << desc << "\n";
        return 0;
      }

    if (vm.count("compression")) {
        cout << "Compression level was set to "
             << vm["compression"].as<double>() << ".\n";
      } else {
            cout << "Compression level was not set.\n";
            }
      }
    catch(exception& e) {
        cerr << "error: " << e.what() << "\n";
        return 1;
    }
    catch(...) {
        cerr << "Exception of unknown type!\n";
    return 1;
    }
return 0;
}

Compile this with

g++ -std=c++11 cmd.cpp -l boost_program_options

And you should be fine

Actually you can leave out "std=c++11" if you want to. I have tried it with both and its ok