Boost.Program_Options: When <bool> is specified as a command-line option, what are valid command-line parameters?

boolean, boost, boost-program-options, c++, command-line-arguments

Solution

Looking at $(BOOST_ROOT)/libs/program_options/src/value_semantic.cpp you can find:

/* Validates bool value.
    Any of "1", "true", "yes", "on" will be converted to "1".<br>
    Any of "0", "false", "no", "off" will be converted to "0".<br>
    Case is ignored. The 'xs' vector can either be empty, in which
    case the value is 'true', or can contain explicit value.
*/
BOOST_PROGRAM_OPTIONS_DECL void validate(any& v, const vector<string>& xs,
                   bool*, int)
{
    check_first_occurrence(v);
    string s(get_single_string(xs, true));

    for (size_t i = 0; i < s.size(); ++i)
        s[i] = char(tolower(s[i]));

    if (s.empty() || s == "on" || s == "yes" || s == "1" || s == "true")
        v = any(true);
    else if (s == "off" || s == "no" || s == "0" || s == "false")
        v = any(false);
    else
        boost::throw_exception(invalid_bool_value(s));
}

Problem

Given the following simple use of Boost.Program_Options: ``` boost::program_options::options_description options("Options"); options.add_options() ("my_bool_flag,b", boost::program_options::value<bool>(), "Sample boolean switch)") ; ``` ... what command-line arguments will evaluate to `false`, and what to `true`? (I.e., assume the program is named "foo", and executed on the command line as: `foo -b ?` ... with the question mark a placeholder for some other text: What are all possible text options that will properly evaluate to `false`, and what to `true`?)

Original source