boost::program_options

boost::program_options

boost::program_options is part of the popular C++ general boost library. This particular library is dedicated to manage command line arguments for your C++ programs.

boost::program_options

Command line parameters are described at the start of your program and are used like any other command line parameters at Unix-style

Example

#include <boost/program_options.hpp>

int main (int argc, char **argv)
{
    namespace po = boost::program_options;
    po::options_description description("Hash Generator usage");
      description.add_options()
        ("help", "show help")
        ("level", po::value<int>(), "Recursive level");

    return 0;
}

We described 2 parameters. The well known help option, and an integer parameter. This piece of code used like this :

./main --help
./main --level 10

Short parameters

If you want to provide short parameters like ./main -h it is very easy. Just need to modify the previous code with :

...
("help,h", "show help")
...

Default value

Of course we can provide default value for a specific flag. Suppose you want to have by default your recursive level set to 5.

...
("level", po::value<int>()->default_value(5), "Recursive level")
...

Multiple values

Suppose now for a specific flag, you would like to be able to specify multiple values such as --flag f1 f2 f3. Easy ! Just need to specifiy a std::vector

("file_pattern", po::value<std::string>()->default_value(".*"), "Pattern on which performing checksum")

Very easy !

Description is good ! Is it difficult to use it ?

Answer is No ! Of course.

po::variables_map vm;
po::parsed_options parsed =
      po::command_line_parser(argc,argv).options(parameters).allow_unregistered().run();

And to check in your program, it a parameter is set or not :

int level;
if (vm.count("level"))
{
    level = vm["level"].as<int>();
}

That's all !

Conclusion

Parsing command line arguments is always boring since we started coding in early ages ! boost::program_options is then a very elegant library for your C++ programs.

Hope you will use it.