impl Stdio

fn piped() -> Stdio

A new pipe should be arranged to connect the parent and child processes.

Examples

With stdout:

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

let output = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::piped())
    .output()
    .expect("process should execute successfully");

assert_eq!(String::from_utf8_lossy(&output.stdout), "Hello, world!\n");
// Nothing echoed to console

With stdin:

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

let mut child = Command::new("rev")
    .stdin(Stdio::piped())
    .stdout(Stdio::piped())
    .spawn()
    .expect("rev command should start");

let mut stdin = child.stdin.take().expect("child stdin should be retrievable");
std::thread::spawn(move || {
    stdin.write_all("Hello, world!".as_bytes()).expect("writing to child stdin should succeed");
});

let output = child.wait_with_output().expect("child stdout should be able to be read");
assert_eq!(String::from_utf8_lossy(&output.stdout), "!dlrow ,olleH");

Writing more than a pipe buffer's worth of input to stdin without also reading stdout and stderr at the same time may cause a deadlock. This is an issue when running any program that doesn't guarantee that it reads its entire stdin before writing more than a pipe buffer's worth of output. The size of a pipe buffer varies on different targets.

fn inherit() -> Stdio

The child inherits from the corresponding parent descriptor.

Examples

With stdout:

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

let output = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::inherit())
    .output()
    .expect("process should execute successfully");

assert_eq!(String::from_utf8_lossy(&output.stdout), "");
// "Hello, world!" echoed to console

With stdin:

use std::process::{Command, Stdio};
use std::io::{self, Write};

let output = Command::new("rev")
    .stdin(Stdio::inherit())
    .stdout(Stdio::piped())
    .output()?;

print!("You piped in the reverse of: ");
io::stdout().write_all(&output.stdout)?;
# io::Result::Ok(())

fn null() -> Stdio

This stream will be ignored. This is the equivalent of attaching the stream to /dev/null.

Examples

With stdout:

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

let output = Command::new("echo")
    .arg("Hello, world!")
    .stdout(Stdio::null())
    .output()
    .expect("process should execute successfully");

assert_eq!(String::from_utf8_lossy(&output.stdout), "");
// Nothing echoed to console

With stdin:

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

let output = Command::new("rev")
    .stdin(Stdio::null())
    .stdout(Stdio::piped())
    .output()
    .expect("process should execute successfully");

assert_eq!(String::from_utf8_lossy(&output.stdout), "");
// Ignores any piped-in input

fn makes_pipe(&self) -> bool

Returns true if this requires Command to create a new pipe.

Example

#![feature(stdio_makes_pipe)]
use std::process::Stdio;

let io = Stdio::piped();
assert_eq!(io.makes_pipe(), true);