Rust by Example

Pipes

The std::Child struct represents a running child process, and exposes the stdin, stdout and stderr handles for interaction with the underlying process via pipes.

use std::io::prelude::*;

use std::process::{Command, Stdio};

static PANGRAM: &'static str =

"the quick brown fox jumped over the lazy dog\n";

fn main() {

// Spawn the `wc` command

let process = match Command::new("wc")

.stdin(Stdio::piped())

.stdout(Stdio::piped())

.spawn() {

Err(why) => panic!("couldn't spawn wc: {}", why),

Ok(process) => process,

};

// Write a string to the `stdin` of `wc`.

//

// `stdin` has type `Option`, but since we know this instance

// must have one, we can directly `unwrap` it.

match process.stdin.unwrap().write_all(PANGRAM.as_bytes()) {

Err(why) => panic!("couldn't write to wc stdin: {}", why),

Ok(_) => println!("sent pangram to wc"),

}

// Because `stdin` does not live after the above calls, it is `drop`ed,

// and the pipe is closed.

//

// This is very important, otherwise `wc` wouldn't start processing the

// input we just sent.

// The `stdout` field also has type `Option` so must be unwrapped.

let mut s = String::new();

match process.stdout.unwrap().read_to_string(&mut s) {

Err(why) => panic!("couldn't read wc stdout: {}", why),

Ok(_) => print!("wc responded with:\n{}", s),

}

}