Simple cross-platform C++ command-line parsing library

qflags uses command-line syntax similar but not equivalent to getopt and getopt_long. qflags can be used as a header-only library or compiled into a static library. Google Test is included as a submodule and will be used to compile and execute gtest binaries if available.

The following build systems are supported via CMake:

• Visual Studio 2013
• Visual Studio 2015
• Visual Studio 2015 Clang/C2*
• GCC (MinGW, Unix)

Other build systems are untested and YMMV.

There are three 'framework' classes:

A trivial program using qflags:

#include <qflags/qflags.h>
#include <cstdio>

int main(int argc, char* argv[])
{
    // Normalize command-line.
    auto command_line = qflags::command_line(argc, argv);
    // Create parser.
    auto parser = qflags::parser();
    
    // Define arguments.
    auto foo = qflags::flag("foo");
    auto bar = qflags::string_option("bar");
    
    // Add arguments to parser.
    parser.add_argument(&foo);
    parser.add_argument(&bar);
    
    // Parse.
    std::string errors;
    if (parser.parse(command_line, &errors)) {
        fprintf(stdout, "'foo' is '%s'\n", foo.value_boolean() ? "true" : "false");
        fprintf(stdout, "'bar' is '%s'\n", bar.value_string().c_str());
    } else {
        fprintf(stdout, "%s", errors.c_str());
    }
    return 0;
}

qflags in general follows the conventions of getopt and getopt_long with some caveats.

• All argument types have a name string; an argument is invoked on the command-line with the argument name prefixed by two dashes, e.g. --foo.
• The parser does not check the length of an argument's name which means it is legal (however inadvisable) to define an argument with a one-character name, e.g. --f.
• If the argument is an option argument with a value then the value follows the argument name separated either by whitespace or an equals sign (=). e.g. --foo bar or --foo=bar.

• Most arguments also have an optional 'short name' which can be invoked on the command-line with the short name prefixed by a single dash, e.g. -f.
• As with the argument name, the parser does not check the length of an argument's short name. This is to allow the use of multibyte characters and multi-character grapheme clusters as short argument names.
• If the argument is an option argument with a value then the value follows the short argument name, optionally separated by whitespace. e.g. -f buzz or -fbuzz.
• When using the short argument name the equals sign is interpreted as part of the value. e.g. -f=buzz yields a value of "=buzz".
• It is not possible to define an argument with only a short name.

TODO :(

1: The string values "true", "True", "TRUE", and "1" evaluate to true. The string values "false", "False", "FALSE", and "0" evaluate to false. Any other string value will emit a parsing error.