clap/examples/tutorial_builder/04_02_parse.rs

// Note: this requires the `cargo` feature

use clap::{arg, command, value_parser};

fn main() {
    let matches = command!()
        .arg(
            arg!(<PORT>)
                .help("Network port to use")
                .value_parser(value_parser!(u16).range(1..)),
        )
        .get_matches();

    // Note, it's safe to call unwrap() because the arg is required
    let port: u16 = *matches
        .get_one::<u16>("PORT")
        .expect("'PORT' is required and parsing will fail if its missing");
    println!("PORT = {}", port);
}