Dealing with sections of INI files with Boost.Program_options

Question

I am trying to parse configuration INI files in Linux. I would like to use Boost and someone pointed me the program options library.

The thing is that I can read lines having the syntax field=value, but how to deal with different sections i.e. lines having [Section_Name] in it? With the code below I have always an exception

Below the code I tried. Thanks AFG

 const char* testFileName = "file.ini";
 std::ifstream s;
 s.open(  testFileName );

 namespace pod = boost::program_options::detail;
 std::set<std::string> options;
 options.insert("a");
 options.insert("b");
 options.insert("c");

 //parser
 for (pod::config_file_iterator i(s, options), e ; i != e; ++i)
 {
    std::cout << i->value[0] << std::endl;
 }

Answer 1

As stated earlier by etarion, the identifier of the option must be prefixed by their enclosing section. Here is a simple modification on your code to demonstrate :

int main()
{
    std::stringstream s(
        "[Test]\n"
        "a = 1\n"
        "b = 2\n"
        "c = test option\n");

    std::set<std::string> options;
    options.insert("Test.a");
    options.insert("Test.b");
    options.insert("Test.c");

    for (boost::program_options::detail::config_file_iterator i(s, options), e ; i != e; ++i)
        std::cout << i->value[0] << std::endl;
}

This program outputs :

1
2
test option

Answer 2

I'm using parse_config_file from program_options, so it may be different, but there the name of the option is SectionName.name if you have something like name=value in [SectionName].

std::string config_filename = "foo.ini";
namespace po = boost::program_options;
po::options_description my_options("Options");
int my_opt;
my_options.add_options()
    ("SectionName.my_opt", po::value(&my_opt)->default_value(64), "My option");
std::ifstream config_stream(config_filename.c_str());
po::variables_map vm;
po::store(po::parse_config_file(config_stream, my_options), vm);
po::notify(vm);
// value is now in my_opt, also accessible by vm["SectionName.my_opt"].as<int>()