Is it possible to have boost::program_options emit a usage message when an unknown option is supplied ? I have code which is parsing its options like this:

void UserAPI::parse_options(const std::vectorstd::string& required_options, int argc, char* argv[], std::string usage) { po::store(po::parse_command_line(argc, argv, options_desc_, options_style_), vm_); po::notify(vm_);

// count how many required options we have

uint count = 0; for (std::vectorstd::string::const_iterator s = required_options.begin(); s != required_options.end(); ++s) { count += vm_.count(*s); }

// if we have a help option, or we don't have all the required options // emit the usage message

if ( vm_.count("help") || count != required_options.size() ) { std::cout << usage << std::endl; std::cout << options_desc_ << std::endl; exit(1); } }

If I pass an unknown option, it seems to be handled automagically:

install/linux/general -orgid ABC -p fred unknown option -p

I don't want this - I want to catch it somehow and emit my usage message, but this seems not to be documented, AFAICS. Anyone know how this can be done ? -- Regards Steve Collyer Netspinner Ltd