Code shared from the Rust Playground

playground.rs

use std::env;
use std::fs::File;
use std::io;
use std::io::Read;
use std::path::Path;

fn read_file(path: &Path) -> io::Result<String> {
    let mut file = File::open(path)?;
    let mut s = String::new();
    file.read_to_string(&mut s).map(|_| s)
}

fn read_args() -> bool {
    eprintln!("Reading from argument file");
    env::args()
        .map(|file| read_file(Path::new(&file)))
        .fold(true, |res, read_res| {
            match read_res {
                Ok(ref contents) => {
                    println!("{}", contents);
                    res
                },
                Err(_) => false,
            }
        })
}

fn read_input() -> bool {
    eprintln!("Reading from input");
    true
}

#[allow(dead_code)]
fn main() -> u32 {
    let result = if env::args().len() > 1 {
        read_args()
    } else {
        read_input()
    };

    result as u32
}