clap/examples/06_positional_args.rs

extern crate clap;

use clap::{App, Arg};

fn main() {

    // Positional arguments are those values after the program name which are not preceded by any
    // identifier (such as "myapp some_file"). Positionals support many of the same options as
    // flags, as well as a few additional ones.
    let matches = App::new("MyApp")
                        // Regular App configuration goes here...

                        // We'll add two positional arguments, a input file, and a config file.
                        //
                        // I'll explain each possible setting that "positionals" accept. Keep in
                        // mind that you DO NOT need to set each of these for every flag, only the
                        // ones that apply to your individual case.
                        .arg(Arg::with_name("input")
                                    .help("the input file to use") // Displayed when showing help info
                                    .index(1)                      // Set the order in which the user must
                                                                   // specify this argument (Starts at 1)
                                    .requires("config")            // Says, "If the user uses "input", 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>)
                                    .required(true)                // By default this argument MUST be present
                                                                   // NOTE: mutual exclusions take precedence over
                                                                   // required arguments
                        )
                        .arg(Arg::with_name("config")
                                    .help("the config file to use")
                                    .index(2))                     // Note, we do not need to specify required(true)
                                                                   // if we don't want to, because "input" already
                                                                   // requires "config"
                                                                   // Note, we also do not need to specify requires("input")
                                                                   // because requires lists are automatically two-way

                        // NOTE: In order to compile this example, comment out mutually_excludes()
                        // because we have not defined an "output" argument.
                        .get_matches();

    // We can find out whether or not "input" or "config" were used
    if matches.is_present("input") {
        println!("An input file was specified");
    }

    // We can also get the values for those arguments
    if let Some(ref in_file) = matches.value_of("input") {
        // It's safe to call unwrap() because of the required options we set above
        println!("Doing work with {} and {}", in_file, matches.value_of("config").unwrap());
    }
    // Continued program logic goes here...
}