boost Boost Program Options Default Values
Example
A default valued command line argument can be specified easily:
// declare options
desc.add_options()
("name", po::value<std::string>()->required(), "Type your name to be greeted!")
("rank", po::value<std::string>()->default_value("Dark Knight"), "Your rank");
Its value is also added to the variable map:
std::cout << "Hello " << vm["name"].as<std::string>() << " " << vm["rank"].as<std::string>() << std::endl;
The default value is shown in the description...
$ ./a.out
Error: the option '--name' is required but missing
Allowed Options:
--name arg Type your name to be greeted!
--rank arg (=Dark Knight) Your rank
... and used if not specified...
$ ./a.out --name Batman
Hello Batman Dark Knight
... but can be overwritten at command line:
$ ./a.out --name Batman --rank FlyingSquirrel
Hello Batman FlyingSquirrel
