main.rs

use std::io::{BufRead, BufReader};
use std::process::{Child, Command, Stdio};

fn main() {
    for id in 1..64_000 {
        let mut child = Command::new("echo").arg(id.to_string())
            .stdout(Stdio::piped()).stderr(Stdio::piped())
            .spawn().unwrap();
        output(&mut child, false);
        child.wait().unwrap();
    }
}


fn output(child: &mut Child, quiet: bool) {
    let stderr = child.stderr.as_mut().expect("unable to open stderr of child");
    let mut stderr_buffer = BufReader::new(stderr).lines();
    if quiet {
        for stderr in stderr_buffer {
            if let Ok(stderr) = stderr {
                println!("{}", stderr);
            } else {
                break
            }
        }
    } else {
        let stdout = child.stdout.as_mut().expect("unable to open stdout of child");
        let mut stdout_buffer = BufReader::new(stdout).lines();

        // Attempt to read from stdout and stderr simultaneously until both are exhausted of messages.
        loop {
            if let Some(stdout) = stdout_buffer.next() {
                // If a message is received from standard output, it will be sent as a `Pipe::Stdout`.
                if let Ok(stdout) = stdout {
                    println!("{}", stdout);
                } else {
                    break
                }
            } else if let Some(stderr) = stderr_buffer.next() {
                if let Ok(stderr) = stderr {
                    println!("{}", stderr);
                } else {
                    break
                }
            } else {
                break
            }
        }
    }
}