How do I create a --help option in a command-line program in c/c++?

Question

I'm pretty sure it's simple. Is there a pre-defined header for create a help context in a command line program.

$ program --help

would provide a list of various help options.

Answer 1

The simplest way to do it in c++ is:

int main(int argc, char** argv)
{
    if(argc == 2 && strcmp(argv[1], "--help")==0)
    {..print help here..}
    return 0;
}

Answer 2

Something along these lines...

int main(int argc, char* argv[])
{
    std::vector<std::string> cmdLineArgs(argv, argv+argc);

    for(auto& arg : cmdLineArgs)
    {
        if(arg == "--help" || arg == "-help")
        {
            std::cout << "Helpful stuff here\n";
        }
        else if(arg == "whatever")
        {
            std::cout << "whatever?!\n";
        }
    }
}

Of course, there are libraries to handle cmd line arguments. But for simple stuff it's really not hard to do yourself.

Answer 3

For C++, you have Boost.Program_options

http://www.boost.org/doc/libs/1_55_0/doc/html/program_options.html

But you'll have to bring the whole boost library (which can be tedious, the first time you do it).

Answer 4

I think you should have a look to this library : Getopt which is part of the GNU C Library. It allows you to parse -like parameters efficiently.

Answer 5

You could do it multiple ways depending on how you want to go about it.

You could use strcmp() and just parse argv[1]:

if(strcmp(argv[1],"--help") == 0)

or you can use getopt if you are running linux:

http://www.gnu.org/software/libc/manual/html_node/Getopt.html

Answer 6

getopt_long is your friend. For one-character options, getopt will suffice.