Rust: reading lines from STDIN and printing them back to console

main.rs

use std::io;

fn main() {
  // Iterate over the lines in io::stdin()
  for line in io::stdin().lines() {
    // Now print the line (line.unwrap() first) via the println!() macro
    println!("{}", line.unwrap());
  }
}

Thanks for this. Here is the whole main.rs that worked for me.

use std::{io, io::prelude::*};

pub type Error = Box<dyn std::error::Error + Send + Sync>;
pub type Result<T> = std::result::Result<T, Error>;

pub fn main() -> Result<()> {
    for line in io::stdin().lock().lines() {
        println!("length = {}", line?.len());
    }
    Ok(())
}

Thanks. This is almost what I was looking for.
So this works for me:

echo "hello" | cargo run

However, the following hangs forever until I enter some value

cargo run

Is there a way to have it stop if nothing was pipped into it?

Thanks. This is almost what I was looking for. So this works for me:

echo "hello" | cargo run

However, the following hangs forever until I enter some value

cargo run

Is there a way to have it stop if nothing was pipped into it?

It has nothing to do with rust but the program is not hanging it is listenings to standard input ( your keyboard) you can type things and to stop it listening you type ctrl-d.