src/test/run-pass/issue-13304.rs

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// ignore-emscripten
#![feature(io, process_capture)]

use std::env;
use std::io::prelude::*;
use std::io;
use std::process::{Command, Stdio};
use std::str;

fn main() {
    let args: Vec<String> = env::args().collect();
    if args.len() > 1 && args[1] == "child" {
        child();
    } else {
        parent();
    }
}

fn parent() {
    let args: Vec<String> = env::args().collect();
    let mut p = Command::new(&args[0]).arg("child")
                        .stdout(Stdio::piped())
                        .stdin(Stdio::piped())
                        .spawn().unwrap();
    p.stdin.as_mut().unwrap().write_all(b"test1\ntest2\ntest3").unwrap();
    let out = p.wait_with_output().unwrap();
    assert!(out.status.success());
    let s = str::from_utf8(&out.stdout).unwrap();
    assert_eq!(s, "test1\ntest2\ntest3\n");
}

fn child() {
    let mut stdin = io::stdin();
    for line in stdin.lock().lines() {
        println!("{}", line.unwrap());
    }
}