src/main.rs

use clap::Parser;
use std::{env, thread, time::Duration};

#[derive(Debug, Parser)]
#[command(author, version, about, long_about = None)]
struct Args {
    #[arg(long, short)]
    message: String,

    #[arg(long, short, default_value_t = 10)]
    wait: u8,
}

fn main() {
    let Args { message, wait } = Args::parse();

    let name = env::var("MY_NAME").unwrap_or(String::from("world"));

    println!("Hello, {name}!");
    println!("Message: {message}");
    println!("Will wait for {wait} seconds");

    thread::sleep(Duration::from_secs(wait as u64));
}