豌豆

下例展示了 program_oprations 的基本用法：为程序定义了 3 个参数: help, host, port . 其中 host 与 port 分别定义了简写 h ,p 。host 是必填项， port 是有缺省值(80)的选填项，当 port 有输入时使用输入项，否则使用缺省值 ，当输入了错误的参数时会输出错误信息。

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

using namespace boost;

int main(int argc, char* argv[])
{
    program_options::options_description desc("Allowed options");
    desc.add_options()
	("help", "help")
	("host,h", program_options::value<std::string>()->required(), "host name")
	("port,p", program_options::value<int>()->default_value(80), "port number");

    program_options::variables_map vm;

    try
    {
	auto ops = program_options::parse_command_line(argc, argv, desc);
	boost::program_options::store(ops, vm);
    }
    catch (boost::program_options::error& e)
    {
	std::cout << e.what() << std::endl;
	return 1;
    }

    if (vm.count("help"))
    {
	std::cout << desc << std::endl;    
    }

    if (!vm.count("host"))
    {
	std::cout << "param is need : " << desc << std::endl;
	return 1;
    }

    //do sth ...

    std::cout << "Host is : "
	<< vm["host"].as<std::string>()
	<< ", Port is : "
	<< vm["port"].as<int>()
	<< std::endl;

    return 0;
}

测试效果：

>testBoostProgramOptions.exe
param is need : Allowed options:
  --help                  help
  -h [ --host ] arg       host name
  -p [ --port ] arg (=80) port number

>testBoostProgramOptions.exe  -h 127.0.0.1
Host is : 127.0.0.1, Port is : 80

>testBoostProgramOptions.exe  -h 127.0.0.1 -p  8080
Host is : 127.0.0.1, Port is : 8080

>testBoostProgramOptions.exe  -h 127.0.0.1 -p  8080  -o er
unrecognised option '-o'

>testBoostProgramOptions.exe  -p  8080
param is need : Allowed options:
  --help                  help
  -h [ --host ] arg       host name
  -p [ --port ] arg (=80) port number