Watch output of tail in rust

main.rs

use std::process::{Command, Stdio, ChildStdout};
use std::io::{Read};
use std::thread;
use std::str;

fn main() {
    let mut command = Command::new("/usr/bin/tail");
    command
        .arg("-f")
        .arg("/var/log/system.log")
        .stdout(Stdio::piped());
    if let Ok(child) = command.spawn() {
        if let Some(mut out) = child.stdout {
            loop {
                let mut chars: [u8; 10] = [0; 10];
                out.read(&mut chars).expect("didn't work");
                print!("{}", str::from_utf8(&chars).unwrap());
            }
        }
    } else {
        println!("Process failed to start");
    }
}