Boost: unrecognised option for positional argument

Question

I'm trying to parse command line with boost 1.58.0. My code is quite simple and copy\pasted from the tutorials. It looks like that:

 try {
        po::options_description desc;
        desc.add_options()
                ("version,v", "Display version of application.");

        po::positional_options_description p;
        p.add("input-file", -1);

        try
        {
            po::store(po::command_line_parser(argc, argv).
                      options(desc).positional(p).run(), vm);

            if ( vm.count("version")  )
            {
                std::cout << "Program version: " << SHUF_T_VERSION << std::endl << "Boost library version: " << BOOST_LIB_VERSION << std::endl;
                return false;
            }

            po::notify(vm); // throws on error, so do after help in case
            // there are any problems
        }
        catch(po::error& e)
        {
            std::cerr << "ERROR: " << e.what() << std::endl << std::endl;
            std::cerr << desc << std::endl;
            return false;
        }

    }
    catch(std::exception& e)
    {
        std::cerr << "Unhandled Exception: "
                  << e.what() << ", application will now exit" << std::endl;
        return false;

    }

  return true;

The whole code is here. The code seems to be correct. The app -v is processed correctly. But if I include any positional arguement, like app myfile the po::store() throws unrecognised option 'myfile'. Any ideas on why this is hapening?

Answer 1

You need to add "input-file" as an option:

po::options_description desc;
desc.add_options()
        ("version,v", "Display version of application.")
        ("input-file", po::value<std::vector<std::string> >(), "input file");

From the tutorial:

The "input-file" option specifies the list of files to process. That's okay for a start, but, of course, writing something like:

compiler --input-file=a.cpp

is a little non-standard, compared with

compiler a.cpp

We'll address this in a moment.

The command line tokens which have no option name, as above, are called "positional options" by this library. They can be handled too. With a little help from the user, the library can decide that "a.cpp" really means the same as "--input-file=a.cpp". Here's the additional code we need:

po::positional_options_description p;
p.add("input-file", -1);

po::variables_map vm;
po::store(po::command_line_parser(ac, av).
          options(desc).positional(p).run(), vm);
po::notify(vm);