extern crate rand; use rand::{OsRng, Rng}; fn main() { // because `OsRng` opens files, it may fail let mut rng = match OsRng::new() { Ok(v) => v, Err(e) => panic!("Failed to obtain OS RNG: {}", e) }; let rand_num: u32 = rng.gen(); println!("{}", rand_num); }