clap/examples/05_flag_args.rs

extern crate clap;

use clap::{App, Arg};

fn main() {

    // Of the three argument types, flags are the most simple. Flags are simple switches which can
    // be either "on" or "off"
    //
    // clap also supports multiple occurrences of flags, the common example is "verbosity" where a
    // user could want a little information with "-v" or tons of information with "-v -v" or "-vv"
    let matches = App::new("MyApp")
                        // Regular App configuration goes here...

                        // We'll add a flag that represents an awesome meter...
                        //
                        // I'll explain each possible setting that "flags" accept. Keep in mind
                        // that you DO NOT need to set each of these for every flag, only the ones
                        // you want for your individual case.
                        .arg(Arg::with_name("awesome")
                                    .help("turns up the awesome") // Displayed when showing help info
                                    .short("a")                   // Trigger this arg with "-a"
                                    .long("awesome")              // Trigger this arg with "--awesome"
                                    .multiple(true)               // This flag should allow multiple
                                                                  // occurrences such as "-aaa" or "-a -a"
                                    .requires("config")           // Says, "If the user uses -a, they MUST
                                                                  // also use this other 'config' arg too"
                                                                  // Can also specifiy a list using
                                                                  // requires_all(Vec<&str>)
                                    .conflicts_with("output")     // Opposite of requires(), says "if the
                                                                  // user uses -a, they CANNOT use 'output'"
                                                                  // also has a mutually_excludes_all(Vec<&str>)
                        )
                        // NOTE: In order to compile this example, comment out requres() and
                        // mutually_excludes() because we have not defined an "output" or "config"
                        // argument.
                        .get_matches();

    // We can find out whether or not awesome was used
    if matches.is_present("awesome") {
        println!("Awesomeness is turned on");
    }

    // If we set the mutliple() option of a flag we can check how many times the user specified
    //
    // Note: if we did not specify the multiple() option, and the user used "awesome" we would get
    // a 1 (no matter how many times they actually used it), or a 0 if they didn't use it at all
    match matches.occurrences_of("awesome") {
        0 => println!("Nothing is awesome"),
        1 => println!("Some things are awesome"),
        2 => println!("Lots of things are awesome"),
        3 | _ => println!("EVERYTHING is awesome!"),
    }

    // Continued program logic goes here...
}