a Rust library for shelling out.
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A cross-platform library for running child processes and building pipelines.

duct wants to make shelling out in Rust as easy and flexible as it is in Bash. It takes care of gotchas and inconsistencies in the way different platforms shell out. And it's a cross-language library; the original implementation is in Python, with an identical API.


  • Version 0.11 introduced the before_spawn method.
  • Version 0.10 changed how environment variable casing is handled on Windows. See the docs for env_remove.
  • Version 0.9 removed the sh function. It now lives in its own crate, duct_sh.


duct tries to be as concise as possible, so that you don't wish you were back writing shell scripts. At the same time, it's explicit about what happens to output, and strict about error codes in child processes.

extern crate duct;

use duct::cmd;

fn main() {
    // Read the name of the current git branch. If git exits with an error
    // code here (because we're not in a git repo, for example), `read` will
    // return an error too.
    let current_branch = cmd!("git", "symbolic-ref", "--short", "HEAD").read().unwrap();

    // Log the current branch, with git taking over the terminal as usual.
    // The `cmd` function works just like the `cmd!` macro, but it takes a
    // collection instead of a variable list of arguments.
    let args = &["log", &current_branch];
    cmd("git", args).run().unwrap();

    // More complicated expressions become trees. Here's a pipeline with two
    // child processes on the left, just because we can. In Bash this would
    // be: stdout=$((echo -n part one "" && echo part two) | sed s/p/sm/g)
    let part_one = &["-n", "part", "one", ""];
    let stdout = cmd("echo", part_one)
        .then(cmd!("echo", "part", "two"))
        .pipe(cmd!("sed", "s/p/sm/g"))
    assert_eq!("smart one smart two", stdout);

duct uses os_pipe internally, and the docs for that one include a big example that takes a dozen lines of code to read both stdout and stderr from a child process. duct can do that in one (moderately long) line:

let output = cmd!("sh", "-c", "echo foo && echo bar 2>&1").stderr_to_stdout().read().unwrap();

assert!(output.split_whitespace().eq(vec!["foo", "bar"]));