boost 程序选项短/长参数名称

Question

我已经实现了一个路由，通过遍历po::variable_map 来打印出我的boost::program_options 对象中可用的所有选项及其当前值。

有了这个，我可以直接打印选项的长名称及其值。但是，我不知道如何从长选项名称中检索短选项名称（即来自 --help 的 -h）。有什么建议吗？

Answer 1

我记得在最近的一个回答中描述了为什么variable_map“为时已晚”无法了解选项描述：

• Boost. Handy variables_map. Taking advantage of having specified the type in the options_desctription

简而言之，variable_map 位于库的 Storage Component 中，因此与选项描述（位于 Options Description Component 中）隔离。

可以做什么？

您可以使用中间结果，即Parsers Component 的原始输出：

解析结果作为parsed_options 类的实例返回。通常，该对象直接传递给存储组件。不过也可以直接使用，也可以做一些额外的处理

所以，让我们在这里尝试制作一个示例：

    po::parsed_options const intermediate = po::parse_command_line(ac, av, desc);

    //////////////////////////////////
    // print the extended usage info as per the question
    //
    for (auto& entry : intermediate.options)
    {
        po::option_description const& opt = desc.find(entry.string_key, false, false, false); 

        std::cout << "\nActual tokens involved: ";
        for (auto& tok : entry.original_tokens)
            std::cout << "'" << tok << "' ";
        for (std::string const& v : entry.value)
            std::cout << "\nAssociated value: " << v;
        std::cout << "\n-----------------------------------------------------------\n";
        std::cout << "opt.format_name()        : "        << opt.format_name()                                      << "\n";
        std::cout << "opt.long_name()          : "        << opt.long_name()                                        << "\n";
        std::cout << "opt.canonical_display_name('-'): "  << opt.canonical_display_name(cls::allow_dash_for_short)  << "\n";
        std::cout << "opt.canonical_display_name('/'): "  << opt.canonical_display_name(cls::allow_slash_for_short) << "\n";
        std::cout << "opt.canonical_display_name('--'): " << opt.canonical_display_name(cls::allow_long)            << "\n";
    }

注意：通过按键查找，您实际上也可以使用variable_map。

打印例如

Actual tokens involved: '-C' '42' 
Associated value: 42
-----------------------------------------------------------
opt.format_name()        : -C [ --compression ]
opt.long_name()          : compression
opt.canonical_display_name('-'): -C
opt.canonical_display_name('/'): /C
opt.canonical_display_name('--'): --compression

Actual tokens involved: '--name' 'santa' 
Associated value: santa
-----------------------------------------------------------
opt.format_name()        : -n [ --name ]
opt.long_name()          : name
opt.canonical_display_name('-'): -n
opt.canonical_display_name('/'): /n
opt.canonical_display_name('--'): --name
Compression level was set to 42.

Live On Coliru

#include <boost/program_options.hpp>
#include <boost/program_options/detail/parsers.hpp>
#include <iostream>

namespace po  = boost::program_options;
namespace cls = po::command_line_style;

int main(int ac, char** av) {
    // Declare the supported options.
    po::options_description desc("Allowed options");
    desc.add_options()
        ("help", "produce help message")
        ("name,n", po::value<std::string>(), "specify the name")
        ("compression,C", po::value<int>(), "set compression level")
        ;

    po::variables_map vm;
    po::parsed_options const intermediate = po::parse_command_line(ac, av, desc);

    //////////////////////////////////
    // print the extended usage info as per the question
    //
    for (auto& entry : intermediate.options)
    {
        po::option_description const& opt = desc.find(entry.string_key, false, false, false); 

        std::cout << "\nActual tokens involved: ";
        for (auto& tok : entry.original_tokens)
            std::cout << "'" << tok << "' ";
        for (std::string const& v : entry.value)
            std::cout << "\nAssociated value: " << v;
        std::cout << "\n-----------------------------------------------------------\n";
        std::cout << "opt.format_name()        : "        << opt.format_name()                                      << "\n";
        std::cout << "opt.long_name()          : "        << opt.long_name()                                        << "\n";
        std::cout << "opt.canonical_display_name('-'): "  << opt.canonical_display_name(cls::allow_dash_for_short)  << "\n";
        std::cout << "opt.canonical_display_name('/'): "  << opt.canonical_display_name(cls::allow_slash_for_short) << "\n";
        std::cout << "opt.canonical_display_name('--'): " << opt.canonical_display_name(cls::allow_long)            << "\n";
    }

    //////////////////////////////////

    po::store(intermediate, vm);
    po::notify(vm);    

    if (vm.count("help")) {
        std::cout << desc << "\n";
        return 1;
    }

    if (vm.count("compression")) {
        std::cout << "Compression level was set to " 
            << vm["compression"].as<int>() << ".\n";
    } else {
        std::cout << "Compression level was not set.\n";
    }
}