How to accept empty value in boost::program_options
boost, boost-program-options, c++
Solution
Please use the `implicit_value` method, e.g
desc.add_options()
("replay,r", po::value<std::string>()->implicit_value("stdin"), "bla bla bla")
This makes the option accept either 0 or 1 token, and if no tokens are provided, it will act as if 'stdin' was provided. Of course, you can pick any other implicit value -- including empty string and '-' as suggested by mch.
Problem
I'm using boost::program_options library to process command line params. I need to accept a file name via -r option, in case if it is empty (-r given without params) I need to use stdin. ``` desc.add_options() ("replay,r", boost::program_options::value<std::string>(), "bla bla bla") ``` In this case boost wouldn't accept -r without params and throw an exception. default_value () option does not work as well as it would make library return value even if user didn't give -r option. Any ideas how to work around?