c++ program_options实现子命令

参考：https://gist.github.com/randomphrase/10801888
code: https://gitee.com/kacakaca/Test/blob/master/basic_cpp/parseoptions.cpp

• 使用g++ -std=c++11 parseoptions.cpp -lboost_program_options编译后， 执行:
  capture command: ./a.out capture --device 2 --stream 1920x1080@30
  control command: ./a.out control -z 150 -m 10,30 -b 128

• 使用options_description的add_options描述参数，例如

  po::options_description desc("Usage");
  desc.add_options()
      ("help,h", "print this message")
      ("[command]", po::value<std::string>(&cmd), "[command] include 'capture', 'control'")
      ("[command_args]", po::value<std::vector<std::string>>(&cmd_args), "args of [command]");
  

  po::options_description command_capture_desc("command capture options");
  command_capture_desc.add_options()
      ("help,h", "")
      ("device,d", po::value<int>(&deviceid)->required(), "specific device number")
      ("stream,s", po::value<std::string>(&stream)->default_value("1920x1080@30"), "specific stream config");
  

  po::options_description command_control_desc("command control options");
  command_control_desc.add_options()
      ("help,h", "capture stream with different zoom, move or brightness camera control value")
      ("zoom,z", po::value<int>(&zoom), "zoom value")
      ("move,m", po::value<std::string>(&move), "move value")
      ("brightness,b", po::value<int>(&brightness), "zoom value");
  

• 其中用到了positional_opions_description, 所以可以实现不同的命令层次， 其中1表示命令的第一个参数，即上面的命令中的‘capture’或‘control’； -1表示任意位置

  po::positional_options_description pos;
  pos.add("[command]", 1)
     .add("[command_args]", -1);
  

• 然后用program_options的相关函数，先处理第一个参数：

  po::parsed_options all_options = po::command_line_parser(argc, argv)
                                          .options(desc)
                                          .positional(pos)
                                          .allow_unregistered()
                                          .run();
  po::store(all_options, vm);
  po::notify(vm);
  

• 然后根据这个参数的不同值进行后续的处理：

  auto opts = po::collect_unrecognized(all_options.options, po::include_positional);
  if (cmd == "capture") {
        
        
      po::store(po::command_line_parser(opts).options(command_capture_desc).run(), vm);
      po::notify(vm);
  
      std::cout << "device number:" << deviceid << std::endl;
      std::cout << "stream config:" << stream << std::endl;
  } else if (cmd == "control") {
        
        
      po::store(po::command_line_parser(opts).options(command_control_desc).run(), vm);
      po::notify(vm);
  
      if (vm.count("zoom") > 0) {
        
        
          std::cout << "zoom:" << zoom << std::endl;
      }
  }