分析位置参数

examples

#include <boost/program_options.hpp>
#include <boost/version.hpp>

#include <iostream>

int
main( int argc, char** argv )
{
    namespace po = boost::program_options;

    po::options_description desc("Options");

    unsigned foo;
    desc.add_options()
        ("help,h", "produce help message")
        ("foo", po::value(&foo), "set foo") 
        ;

    po::variables_map vm;
    try {
        po::store(
                po::parse_command_line( argc, argv, desc ),
                vm
                );
        po::notify( vm );

        if ( vm.count("help") ) {
            std::cout << desc << "\n";
            std::cout << "boost version: " << BOOST_LIB_VERSION << std::endl;
        }
    } catch ( const boost::program_options::error& e ) {
        std::cerr << e.what() << std::endl;
    }
}

以下行为符合预期:

samm$ ./a.out -h
Options:
  -h [ --help ]         produce help message
  --foo arg             set foo

boost version: 1_44
samm$ ./a.out --help
Options:
  -h [ --help ]         produce help message
  --foo arg             set foo

boost version: 1_44
samm$ ./a.out --foo 1
samm$ ./a.out --asdf
unknown option asdf
samm$

然而,当引入位置参数时,我很惊讶,它没有被标记为错误

samm$ ./a.out foo bar baz
samm$

boost::program_options::too_many_positional_options_error 未引发异常?