[Boost-users] program_options: emit usage message on unknown option ?

From: Stephen Collyer (scollyer_at_[hidden])
Date: 2008-06-06 12:06:40

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::vector<std::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::vector<std::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