I've found an answer for my question, When defining an option with no value via value-permitted interface, one must pass not boost::program_options::typed_value() as semantics, but bool_switch(). This means that no value can be explicitly taken for this option from the command line. One can see this question at stackoverflow: http://stackoverflow.com/questions/7174781/boost-program-options-notifier-fo... Regards, Dmitriy. On 29 August 2011 15:16, Dmitriy Matison <matison.d@gmail.com> wrote:

Hello,

I'm wondering if there is a possibility to make program_options library to notify me automatically when option with no value is passed? As far as I understand this feature exists only for options with defined value_semantic. But this means I must permit passing a value for such options. Say, I make an option with zero_tokens() semantics so it can be passed without value and throw an error if some value was provided. Unfortunately, this doesn't solve the problem if you have positional options. In that case a positional option following a no-value option will be parsed as this option's value. I can't set notifier for options with no value? This is something not understandable. I even think of some patch to be added to the lib.

Regards, Dmitriy.