Duct is a library for running child processes. Duct makes it easy to build pipelines and redirect IO like a shell. At the same time, Duct helps you write correct, portable code: whitespace is never significant, errors from child processes get reported by default, and a variety of gotchas, bugs, and platform inconsistencies are handled for you the Right Way™.

• Documentation
• Crate
• GitHub repo
• the same library, in Python

Run a command without capturing any output. Here "hi" is printed directly to the terminal:

use duct::cmd;
cmd!("echo", "hi").run()?;

Capture the standard output of a command. Here "hi" is returned as a String:

let stdout = cmd!("echo", "hi").read()?;
assert_eq!(stdout, "hi");

Capture the standard output of a pipeline:

let stdout = cmd!("echo", "hi").pipe(cmd!("sed", "s/i/o/")).read()?;
assert_eq!(stdout, "ho");

Merge standard error into standard output and read both incrementally:

use duct::cmd;
use std::io::prelude::*;
use std::io::BufReader;

let big_cmd = cmd!("bash", "-c", "echo out && echo err 1>&2");
let reader = big_cmd.stderr_to_stdout().reader()?;
let mut lines = BufReader::new(reader).lines();
assert_eq!(lines.next().unwrap()?, "out");
assert_eq!(lines.next().unwrap()?, "err");

Children that exit with a non-zero status return an error by default:

let result = cmd!("false").run();
assert!(result.is_err());
let result = cmd!("false").unchecked().run();
assert!(result.is_ok());