How to Use stdin and stdout in Rust

Use std::io to read from standard input and println! to write to standard output.

use std::io;

fn main() {
    println!("Please input your guess.");
    let mut guess = String::new();
    io::stdin()
        .read_line(&mut guess)
        .expect("Failed to read line");
    println!("You guessed: {guess}");
}

Standard input is how your program receives text typed by the user, while standard output is how your program displays text back to them. Think of it like a conversation where stdin is listening to what the user says and stdout is your program speaking back. You use this pattern whenever you need a command-line tool to interact with a human.