Read one parameter from config file where there are more parameters, with boost program_options

Question

I have a cfg file as the following:

parameter1="hello" parameter2=22 parameter3=12

Using boost_program to read all the parameters works fine with this code:

po::options_description options("Options"); options.add_options() ("help,h", "produce help message") ("parameter1", po::value<string>(&parameter1)->default_value("bye"), "parameter1") ("parameter2", po::value<int>(&parameter2)->default_value(2), "parameter2") ("parameter3", po::value<int>(&parameter3)->default_value(4), "parameter3"); po::variables_map vm; po::store(po::parse_command_line(argc, argv, options), vm); notify(vm); try { po::store(po::parse_config_file< char >(filePath, options), vm); } catch (const std::exception& e) { std::cerr << "Error parsing file: " << filePath << ": " << e.what() << std::endl; }

...

But when I try to do a generic method where i just want to read one parameter given from a call, I have an error parsing.

I want to read the second parameter for instance, so I write this:

const char parameter_string = "parameter2"; int default = 30; int parameter; getparameter(parameter_string,parameter,default);

and goes to the method getsparameter where this is what I have this time: ...

po::options_description options("Options"); options.add_options() ("help,h", "produce help message") (parameter_string, po::value<int>(&parameter)->default_value(default), "reading parameter"); po::variables_map vm; po::store(po::parse_command_line(argc, argv, options), vm); notify(vm);

but the error is:

Error parsing file: file.cfg: unknown option parameter1

So my question is if it is posible to read only one parameter from a file or it is necessary to parse all the parameters with boost_program in options.add_option including as many lines as parameters I write in the config file and then take the value from the parameter I want.

Jaffa · Accepted Answer · 2013-03-05 17:50:50Z

Use allow_unregistered function :

Specifies that unregistered options are allowed and should be passed though. For each command like token that looks like an option but does not contain a recognized name, an instance of basic_option will be added to result, with 'unrecognized' field set to 'true'. It's possible to collect all unrecognized options with the 'collect_unrecognized' funciton.

user2136529 · Accepted Answer · 2013-03-06 09:15:02Z

As I an using "parse_config_file" I see in the documentation that "allow_unregistered" is set to false by default.

template<typename charT> BOOST_PROGRAM_OPTIONS_DECL basic_parsed_options< charT > parse_config_file(std::basic_istream< charT > &, const options_description &, bool allow_unregistered = false);

So i modified my line like this:

Old code:

po::store(po::parse_config_file< char >(filePath, options), vm);

New code:

po::store(po::parse_config_file< char >(filePath, options, true), vm);

And as I said, It works. Thank you for your answer.

Collectives™ on Stack Overflow

Read one parameter from config file where there are more parameters, with boost program_options

2 Answers 2

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Related