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async-process
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//! Async interface for working with processes.
//!
//! This crate is an async version of [`std::process`].
//!
//! # Implementation
//!
//! A background thread named "async-process" is lazily created on first use, which waits for
//! spawned child processes to exit and then calls the `wait()` syscall to clean up the "zombie"
//! processes. This is unlike the `process` API in the standard library, where dropping a running
//! `Child` leaks its resources.
//!
//! This crate uses [`async-io`] for async I/O on Unix-like systems and [`blocking`] for async I/O
//! on Windows.
//!
//! [`async-io`]: https://docs.rs/async-io
//! [`blocking`]: https://docs.rs/blocking
//!
//! # Examples
//!
//! Spawn a process and collect its output:
//!
//! ```no_run
//! # futures_lite::future::block_on(async {
//! use async_process::Command;
//!
//! let out = Command::new("echo").arg("hello").arg("world").output().await?;
//! assert_eq!(out.stdout, b"hello world\n");
//! # std::io::Result::Ok(()) });
//! ```
//!
//! Read the output line-by-line as it gets produced:
//!
//! ```no_run
//! # futures_lite::future::block_on(async {
//! use async_process::{Command, Stdio};
//! use futures_lite::{io::BufReader, prelude::*};
//!
//! let mut child = Command::new("find")
//! .arg(".")
//! .stdout(Stdio::piped())
//! .spawn()?;
//!
//! let mut lines = BufReader::new(child.stdout.take().unwrap()).lines();
//!
//! while let Some(line) = lines.next().await {
//! println!("{}", line?);
//! }
//! # std::io::Result::Ok(()) });
//! ```
#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
#![doc(
html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
)]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
)]
use std::convert::Infallible;
use std::ffi::OsStr;
use std::fmt;
use std::path::Path;
use std::pin::Pin;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll};
use std::thread;
#[cfg(unix)]
use async_io::Async;
#[cfg(unix)]
use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, OwnedFd, RawFd};
#[cfg(windows)]
use blocking::Unblock;
use async_lock::OnceCell;
use futures_lite::{future, io, prelude::*};
#[doc(no_inline)]
pub use std::process::{ExitStatus, Output, Stdio};
#[cfg(unix)]
pub mod unix;
#[cfg(windows)]
pub mod windows;
mod reaper;
mod sealed {
pub trait Sealed {}
}
#[cfg(test)]
static DRIVER_THREAD_SPAWNED: std::sync::atomic::AtomicBool =
std::sync::atomic::AtomicBool::new(false);
/// The zombie process reaper.
///
/// This structure reaps zombie processes and emits the `SIGCHLD` signal.
struct Reaper {
/// Underlying system reaper.
sys: reaper::Reaper,
/// The number of tasks polling the SIGCHLD event.
///
/// If this is zero, the `async-process` thread must be spawned.
drivers: AtomicUsize,
/// Number of live `Child` instances currently running.
///
/// This is used to prevent the reaper thread from being spawned right as the program closes,
/// when the reaper thread isn't needed. This represents the number of active processes.
child_count: AtomicUsize,
}
impl Reaper {
/// Get the singleton instance of the reaper.
fn get() -> &'static Self {
static REAPER: OnceCell<Reaper> = OnceCell::new();
REAPER.get_or_init_blocking(|| Reaper {
sys: reaper::Reaper::new(),
drivers: AtomicUsize::new(0),
child_count: AtomicUsize::new(0),
})
}
/// Ensure that the reaper is driven.
///
/// If there are no active `driver()` callers, this will spawn the `async-process` thread.
#[inline]
fn ensure_driven(&'static self) {
if self
.drivers
.compare_exchange(0, 1, Ordering::SeqCst, Ordering::Acquire)
.is_ok()
{
self.start_driver_thread();
}
}
/// Start the `async-process` thread.
#[cold]
fn start_driver_thread(&'static self) {
#[cfg(test)]
DRIVER_THREAD_SPAWNED
.compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
.unwrap_or_else(|_| unreachable!("Driver thread already spawned"));
thread::Builder::new()
.name("async-process".to_string())
.spawn(move || {
let driver = async move {
// No need to bump self.drivers, it was already bumped in ensure_driven.
let guard = self.sys.lock().await;
self.sys.reap(guard).await
};
#[cfg(unix)]
async_io::block_on(driver);
#[cfg(not(unix))]
future::block_on(driver);
})
.expect("cannot spawn async-process thread");
}
/// Register a process with this reaper.
fn register(&'static self, child: std::process::Child) -> io::Result<reaper::ChildGuard> {
self.ensure_driven();
self.sys.register(child)
}
}
cfg_if::cfg_if! {
if #[cfg(windows)] {
// Wraps a sync I/O type into an async I/O type.
fn wrap<T>(io: T) -> io::Result<Unblock<T>> {
Ok(Unblock::new(io))
}
} else if #[cfg(unix)] {
/// Wrap a file descriptor into a non-blocking I/O type.
fn wrap<T: std::os::unix::io::AsFd>(io: T) -> io::Result<Async<T>> {
Async::new(io)
}
}
}
/// A guard that can kill child processes, or push them into the zombie list.
struct ChildGuard {
inner: reaper::ChildGuard,
reap_on_drop: bool,
kill_on_drop: bool,
reaper: &'static Reaper,
}
impl ChildGuard {
fn get_mut(&mut self) -> &mut std::process::Child {
self.inner.get_mut()
}
}
// When the last reference to the child process is dropped, push it into the zombie list.
impl Drop for ChildGuard {
fn drop(&mut self) {
if self.kill_on_drop {
self.get_mut().kill().ok();
}
if self.reap_on_drop {
self.inner.reap(&self.reaper.sys);
}
// Decrement number of children.
self.reaper.child_count.fetch_sub(1, Ordering::Acquire);
}
}
/// A spawned child process.
///
/// The process can be in running or exited state. Use [`status()`][`Child::status()`] or
/// [`output()`][`Child::output()`] to wait for it to exit.
///
/// If the [`Child`] is dropped, the process keeps running in the background.
///
/// # Examples
///
/// Spawn a process and wait for it to complete:
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// Command::new("cp").arg("a.txt").arg("b.txt").status().await?;
/// # std::io::Result::Ok(()) });
/// ```
pub struct Child {
/// The handle for writing to the child's standard input (stdin), if it has been captured.
pub stdin: Option<ChildStdin>,
/// The handle for reading from the child's standard output (stdout), if it has been captured.
pub stdout: Option<ChildStdout>,
/// The handle for reading from the child's standard error (stderr), if it has been captured.
pub stderr: Option<ChildStderr>,
/// The inner child process handle.
child: Arc<Mutex<ChildGuard>>,
}
impl Child {
/// Wraps the inner child process handle and registers it in the global process list.
///
/// The "async-process" thread waits for processes in the global list and cleans up the
/// resources when they exit.
fn new(cmd: &mut Command) -> io::Result<Child> {
// Make sure the reaper exists before we spawn the child process.
let reaper = Reaper::get();
let mut child = cmd.inner.spawn()?;
// Convert sync I/O types into async I/O types.
let stdin = child.stdin.take().map(wrap).transpose()?.map(ChildStdin);
let stdout = child.stdout.take().map(wrap).transpose()?.map(ChildStdout);
let stderr = child.stderr.take().map(wrap).transpose()?.map(ChildStderr);
// Bump the child count.
reaper.child_count.fetch_add(1, Ordering::Relaxed);
// Register the child process in the global list.
let inner = reaper.register(child)?;
Ok(Child {
stdin,
stdout,
stderr,
child: Arc::new(Mutex::new(ChildGuard {
inner,
reap_on_drop: cmd.reap_on_drop,
kill_on_drop: cmd.kill_on_drop,
reaper,
})),
})
}
/// Returns the OS-assigned process identifier associated with this child.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let mut child = Command::new("ls").spawn()?;
/// println!("id: {}", child.id());
/// # std::io::Result::Ok(()) });
/// ```
pub fn id(&self) -> u32 {
self.child.lock().unwrap().get_mut().id()
}
/// Forces the child process to exit.
///
/// If the child has already exited, an [`InvalidInput`] error is returned.
///
/// This is equivalent to sending a SIGKILL on Unix platforms.
///
/// [`InvalidInput`]: `std::io::ErrorKind::InvalidInput`
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let mut child = Command::new("yes").spawn()?;
/// child.kill()?;
/// println!("exit status: {}", child.status().await?);
/// # std::io::Result::Ok(()) });
/// ```
pub fn kill(&mut self) -> io::Result<()> {
self.child.lock().unwrap().get_mut().kill()
}
/// Returns the exit status if the process has exited.
///
/// Unlike [`status()`][`Child::status()`], this method will not drop the stdin handle.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let mut child = Command::new("ls").spawn()?;
///
/// match child.try_status()? {
/// None => println!("still running"),
/// Some(status) => println!("exited with: {}", status),
/// }
/// # std::io::Result::Ok(()) });
/// ```
pub fn try_status(&mut self) -> io::Result<Option<ExitStatus>> {
self.child.lock().unwrap().get_mut().try_wait()
}
/// Drops the stdin handle and waits for the process to exit.
///
/// Closing the stdin of the process helps avoid deadlocks. It ensures that the process does
/// not block waiting for input from the parent process while the parent waits for the child to
/// exit.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::{Command, Stdio};
///
/// let mut child = Command::new("cp")
/// .arg("a.txt")
/// .arg("b.txt")
/// .spawn()?;
///
/// println!("exit status: {}", child.status().await?);
/// # std::io::Result::Ok(()) });
/// ```
pub fn status(&mut self) -> impl Future<Output = io::Result<ExitStatus>> {
self.stdin.take();
let child = self.child.clone();
async move { Reaper::get().sys.status(&child).await }
}
/// Drops the stdin handle and collects the output of the process.
///
/// Closing the stdin of the process helps avoid deadlocks. It ensures that the process does
/// not block waiting for input from the parent process while the parent waits for the child to
/// exit.
///
/// In order to capture the output of the process, [`Command::stdout()`] and
/// [`Command::stderr()`] must be configured with [`Stdio::piped()`].
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::{Command, Stdio};
///
/// let child = Command::new("ls")
/// .stdout(Stdio::piped())
/// .stderr(Stdio::piped())
/// .spawn()?;
///
/// let out = child.output().await?;
/// # std::io::Result::Ok(()) });
/// ```
pub fn output(mut self) -> impl Future<Output = io::Result<Output>> {
// A future that waits for the exit status.
let status = self.status();
// A future that collects stdout.
let stdout = self.stdout.take();
let stdout = async move {
let mut v = Vec::new();
if let Some(mut s) = stdout {
s.read_to_end(&mut v).await?;
}
io::Result::Ok(v)
};
// A future that collects stderr.
let stderr = self.stderr.take();
let stderr = async move {
let mut v = Vec::new();
if let Some(mut s) = stderr {
s.read_to_end(&mut v).await?;
}
io::Result::Ok(v)
};
async move {
let (stdout, stderr) = future::try_zip(stdout, stderr).await?;
let status = status.await?;
Ok(Output {
status,
stdout,
stderr,
})
}
}
}
impl fmt::Debug for Child {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Child")
.field("stdin", &self.stdin)
.field("stdout", &self.stdout)
.field("stderr", &self.stderr)
.finish()
}
}
/// A handle to a child process's standard input (stdin).
///
/// When a [`ChildStdin`] is dropped, the underlying handle gets closed. If the child process was
/// previously blocked on input, it becomes unblocked after dropping.
#[derive(Debug)]
pub struct ChildStdin(
#[cfg(windows)] Unblock<std::process::ChildStdin>,
#[cfg(unix)] Async<std::process::ChildStdin>,
);
impl ChildStdin {
/// Convert async_process::ChildStdin into std::process::Stdio.
///
/// You can use it to associate to the next process.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
/// use std::process::Stdio;
///
/// let mut ls_child = Command::new("ls").stdin(Stdio::piped()).spawn()?;
/// let stdio:Stdio = ls_child.stdin.take().unwrap().into_stdio().await?;
///
/// let mut echo_child = Command::new("echo").arg("./").stdout(stdio).spawn()?;
///
/// # std::io::Result::Ok(()) });
/// ```
pub async fn into_stdio(self) -> io::Result<std::process::Stdio> {
cfg_if::cfg_if! {
if #[cfg(windows)] {
Ok(self.0.into_inner().await.into())
} else if #[cfg(unix)] {
let child_stdin = self.0.into_inner()?;
blocking_fd(rustix::fd::AsFd::as_fd(&child_stdin))?;
Ok(child_stdin.into())
}
}
}
}
impl io::AsyncWrite for ChildStdin {
fn poll_write(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
Pin::new(&mut self.0).poll_write(cx, buf)
}
fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
Pin::new(&mut self.0).poll_flush(cx)
}
fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
Pin::new(&mut self.0).poll_close(cx)
}
}
#[cfg(unix)]
impl AsRawFd for ChildStdin {
fn as_raw_fd(&self) -> RawFd {
self.0.as_raw_fd()
}
}
#[cfg(unix)]
impl AsFd for ChildStdin {
fn as_fd(&self) -> BorrowedFd<'_> {
self.0.as_fd()
}
}
#[cfg(unix)]
impl TryFrom<ChildStdin> for OwnedFd {
type Error = io::Error;
fn try_from(value: ChildStdin) -> Result<Self, Self::Error> {
value.0.try_into()
}
}
// TODO(notgull): Add mirroring AsRawHandle impls for all of the child handles
//
// at the moment this is pretty hard to do because of how they're wrapped in
// Unblock, meaning that we can't always access the underlying handle. async-fs
// gets around this by putting the handle in an Arc, but there's still some decision
// to be made about how to handle this (no pun intended)
/// A handle to a child process's standard output (stdout).
///
/// When a [`ChildStdout`] is dropped, the underlying handle gets closed.
#[derive(Debug)]
pub struct ChildStdout(
#[cfg(windows)] Unblock<std::process::ChildStdout>,
#[cfg(unix)] Async<std::process::ChildStdout>,
);
impl ChildStdout {
/// Convert async_process::ChildStdout into std::process::Stdio.
///
/// You can use it to associate to the next process.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
/// use std::process::Stdio;
/// use std::io::Read;
/// use futures_lite::AsyncReadExt;
///
/// let mut ls_child = Command::new("ls").stdout(Stdio::piped()).spawn()?;
/// let stdio:Stdio = ls_child.stdout.take().unwrap().into_stdio().await?;
///
/// let mut echo_child = Command::new("echo").stdin(stdio).stdout(Stdio::piped()).spawn()?;
/// let mut buf = vec![];
/// echo_child.stdout.take().unwrap().read(&mut buf).await;
/// # std::io::Result::Ok(()) });
/// ```
pub async fn into_stdio(self) -> io::Result<std::process::Stdio> {
cfg_if::cfg_if! {
if #[cfg(windows)] {
Ok(self.0.into_inner().await.into())
} else if #[cfg(unix)] {
let child_stdout = self.0.into_inner()?;
blocking_fd(rustix::fd::AsFd::as_fd(&child_stdout))?;
Ok(child_stdout.into())
}
}
}
}
impl io::AsyncRead for ChildStdout {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
Pin::new(&mut self.0).poll_read(cx, buf)
}
}
#[cfg(unix)]
impl AsRawFd for ChildStdout {
fn as_raw_fd(&self) -> RawFd {
self.0.as_raw_fd()
}
}
#[cfg(unix)]
impl AsFd for ChildStdout {
fn as_fd(&self) -> BorrowedFd<'_> {
self.0.as_fd()
}
}
#[cfg(unix)]
impl TryFrom<ChildStdout> for OwnedFd {
type Error = io::Error;
fn try_from(value: ChildStdout) -> Result<Self, Self::Error> {
value.0.try_into()
}
}
/// A handle to a child process's standard error (stderr).
///
/// When a [`ChildStderr`] is dropped, the underlying handle gets closed.
#[derive(Debug)]
pub struct ChildStderr(
#[cfg(windows)] Unblock<std::process::ChildStderr>,
#[cfg(unix)] Async<std::process::ChildStderr>,
);
impl ChildStderr {
/// Convert async_process::ChildStderr into std::process::Stdio.
///
/// You can use it to associate to the next process.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
/// use std::process::Stdio;
///
/// let mut ls_child = Command::new("ls").arg("x").stderr(Stdio::piped()).spawn()?;
/// let stdio:Stdio = ls_child.stderr.take().unwrap().into_stdio().await?;
///
/// let mut echo_child = Command::new("echo").stdin(stdio).spawn()?;
/// # std::io::Result::Ok(()) });
/// ```
pub async fn into_stdio(self) -> io::Result<std::process::Stdio> {
cfg_if::cfg_if! {
if #[cfg(windows)] {
Ok(self.0.into_inner().await.into())
} else if #[cfg(unix)] {
let child_stderr = self.0.into_inner()?;
blocking_fd(rustix::fd::AsFd::as_fd(&child_stderr))?;
Ok(child_stderr.into())
}
}
}
}
impl io::AsyncRead for ChildStderr {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
Pin::new(&mut self.0).poll_read(cx, buf)
}
}
#[cfg(unix)]
impl AsRawFd for ChildStderr {
fn as_raw_fd(&self) -> RawFd {
self.0.as_raw_fd()
}
}
#[cfg(unix)]
impl AsFd for ChildStderr {
fn as_fd(&self) -> BorrowedFd<'_> {
self.0.as_fd()
}
}
#[cfg(unix)]
impl TryFrom<ChildStderr> for OwnedFd {
type Error = io::Error;
fn try_from(value: ChildStderr) -> Result<Self, Self::Error> {
value.0.try_into()
}
}
/// Runs the driver for the asynchronous processes.
///
/// This future takes control of global structures related to driving [`Child`]ren and reaping
/// zombie processes. These responsibilities include listening for the `SIGCHLD` signal and
/// making sure zombie processes are successfully waited on.
///
/// If multiple tasks run `driver()` at once, only one will actually drive the reaper; the other
/// ones will just sleep. If a task that is driving the reaper is dropped, a previously sleeping
/// task will take over. If all tasks driving the reaper are dropped, the "async-process" thread
/// will be spawned. The "async-process" thread just blocks on this future and will automatically
/// be spawned if no tasks are driving the reaper once a [`Child`] is created.
///
/// This future will never complete. It is intended to be ran on a background task in your
/// executor of choice.
///
/// # Examples
///
/// ```no_run
/// use async_executor::Executor;
/// use async_process::{driver, Command};
///
/// # futures_lite::future::block_on(async {
/// // Create an executor and run on it.
/// let ex = Executor::new();
/// ex.run(async {
/// // Run the driver future in the background.
/// ex.spawn(driver()).detach();
///
/// // Run a command.
/// Command::new("ls").output().await.ok();
/// }).await;
/// # });
/// ```
#[allow(clippy::manual_async_fn)]
#[inline]
pub fn driver() -> impl Future<Output = Infallible> + Send + 'static {
async {
// Get the reaper.
let reaper = Reaper::get();
// Make sure the reaper knows we're driving it.
reaper.drivers.fetch_add(1, Ordering::SeqCst);
// Decrement the driver count when this future is dropped.
let _guard = CallOnDrop(|| {
let prev_count = reaper.drivers.fetch_sub(1, Ordering::SeqCst);
// If this was the last driver, and there are still resources actively using the
// reaper, make sure that there is a thread driving the reaper.
if prev_count == 1
&& (reaper.child_count.load(Ordering::SeqCst) > 0 || reaper.sys.has_zombies())
{
reaper.ensure_driven();
}
});
// Acquire the reaper lock and start polling the SIGCHLD event.
let guard = reaper.sys.lock().await;
reaper.sys.reap(guard).await
}
}
/// A builder for spawning processes.
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let output = if cfg!(target_os = "windows") {
/// Command::new("cmd").args(&["/C", "echo hello"]).output().await?
/// } else {
/// Command::new("sh").arg("-c").arg("echo hello").output().await?
/// };
/// # std::io::Result::Ok(()) });
/// ```
pub struct Command {
inner: std::process::Command,
stdin: bool,
stdout: bool,
stderr: bool,
reap_on_drop: bool,
kill_on_drop: bool,
}
impl Command {
/// Constructs a new [`Command`] for launching `program`.
///
/// The initial configuration (the working directory and environment variables) is inherited
/// from the current process.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("ls");
/// ```
pub fn new<S: AsRef<OsStr>>(program: S) -> Command {
Self::from(std::process::Command::new(program))
}
/// Adds a single argument to pass to the program.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("echo");
/// cmd.arg("hello");
/// cmd.arg("world");
/// ```
pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Command {
self.inner.arg(arg);
self
}
/// Adds multiple arguments to pass to the program.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("echo");
/// cmd.args(&["hello", "world"]);
/// ```
pub fn args<I, S>(&mut self, args: I) -> &mut Command
where
I: IntoIterator<Item = S>,
S: AsRef<OsStr>,
{
self.inner.args(args);
self
}
/// Configures an environment variable for the new process.
///
/// Note that environment variable names are case-insensitive (but case-preserving) on Windows,
/// and case-sensitive on all other platforms.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("ls");
/// cmd.env("PATH", "/bin");
/// ```
pub fn env<K, V>(&mut self, key: K, val: V) -> &mut Command
where
K: AsRef<OsStr>,
V: AsRef<OsStr>,
{
self.inner.env(key, val);
self
}
/// Configures multiple environment variables for the new process.
///
/// Note that environment variable names are case-insensitive (but case-preserving) on Windows,
/// and case-sensitive on all other platforms.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("ls");
/// cmd.envs(vec![("PATH", "/bin"), ("TERM", "xterm-256color")]);
/// ```
pub fn envs<I, K, V>(&mut self, vars: I) -> &mut Command
where
I: IntoIterator<Item = (K, V)>,
K: AsRef<OsStr>,
V: AsRef<OsStr>,
{
self.inner.envs(vars);
self
}
/// Removes an environment variable mapping.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("ls");
/// cmd.env_remove("PATH");
/// ```
pub fn env_remove<K: AsRef<OsStr>>(&mut self, key: K) -> &mut Command {
self.inner.env_remove(key);
self
}
/// Removes all environment variable mappings.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("ls");
/// cmd.env_clear();
/// ```
pub fn env_clear(&mut self) -> &mut Command {
self.inner.env_clear();
self
}
/// Configures the working directory for the new process.
///
/// # Examples
///
/// ```
/// use async_process::Command;
///
/// let mut cmd = Command::new("ls");
/// cmd.current_dir("/");
/// ```
pub fn current_dir<P: AsRef<Path>>(&mut self, dir: P) -> &mut Command {
self.inner.current_dir(dir);
self
}
/// Configures the standard input (stdin) for the new process.
///
/// # Examples
///
/// ```
/// use async_process::{Command, Stdio};
///
/// let mut cmd = Command::new("cat");
/// cmd.stdin(Stdio::null());
/// ```
pub fn stdin<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
self.stdin = true;
self.inner.stdin(cfg);
self
}
/// Configures the standard output (stdout) for the new process.
///
/// # Examples
///
/// ```
/// use async_process::{Command, Stdio};
///
/// let mut cmd = Command::new("ls");
/// cmd.stdout(Stdio::piped());
/// ```
pub fn stdout<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
self.stdout = true;
self.inner.stdout(cfg);
self
}
/// Configures the standard error (stderr) for the new process.
///
/// # Examples
///
/// ```
/// use async_process::{Command, Stdio};
///
/// let mut cmd = Command::new("ls");
/// cmd.stderr(Stdio::piped());
/// ```
pub fn stderr<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
self.stderr = true;
self.inner.stderr(cfg);
self
}
/// Configures whether to reap the zombie process when [`Child`] is dropped.
///
/// When the process finishes, it becomes a "zombie" and some resources associated with it
/// remain until [`Child::try_status()`], [`Child::status()`], or [`Child::output()`] collects
/// its exit code.
///
/// If its exit code is never collected, the resources may leak forever. This crate has a
/// background thread named "async-process" that collects such "zombie" processes and then
/// "reaps" them, thus preventing the resource leaks.
///
/// The default value of this option is `true`.
///
/// # Examples
///
/// ```
/// use async_process::{Command, Stdio};
///
/// let mut cmd = Command::new("cat");
/// cmd.reap_on_drop(false);
/// ```
pub fn reap_on_drop(&mut self, reap_on_drop: bool) -> &mut Command {
self.reap_on_drop = reap_on_drop;
self
}
/// Configures whether to kill the process when [`Child`] is dropped.
///
/// The default value of this option is `false`.
///
/// # Examples
///
/// ```
/// use async_process::{Command, Stdio};
///
/// let mut cmd = Command::new("cat");
/// cmd.kill_on_drop(true);
/// ```
pub fn kill_on_drop(&mut self, kill_on_drop: bool) -> &mut Command {
self.kill_on_drop = kill_on_drop;
self
}
/// Executes the command and returns the [`Child`] handle to it.
///
/// If not configured, stdin, stdout and stderr will be set to [`Stdio::inherit()`].
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let child = Command::new("ls").spawn()?;
/// # std::io::Result::Ok(()) });
/// ```
pub fn spawn(&mut self) -> io::Result<Child> {
if !self.stdin {
self.inner.stdin(Stdio::inherit());
}
if !self.stdout {
self.inner.stdout(Stdio::inherit());
}
if !self.stderr {
self.inner.stderr(Stdio::inherit());
}
Child::new(self)
}
/// Executes the command, waits for it to exit, and returns the exit status.
///
/// If not configured, stdin, stdout and stderr will be set to [`Stdio::inherit()`].
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let status = Command::new("cp")
/// .arg("a.txt")
/// .arg("b.txt")
/// .status()
/// .await?;
/// # std::io::Result::Ok(()) });
/// ```
pub fn status(&mut self) -> impl Future<Output = io::Result<ExitStatus>> {
let child = self.spawn();
async { child?.status().await }
}
/// Executes the command and collects its output.
///
/// If not configured, stdin will be set to [`Stdio::null()`], and stdout and stderr will be
/// set to [`Stdio::piped()`].
///
/// # Examples
///
/// ```no_run
/// # futures_lite::future::block_on(async {
/// use async_process::Command;
///
/// let output = Command::new("cat")
/// .arg("a.txt")
/// .output()
/// .await?;
/// # std::io::Result::Ok(()) });
/// ```
pub fn output(&mut self) -> impl Future<Output = io::Result<Output>> {
if !self.stdin {
self.inner.stdin(Stdio::null());
}
if !self.stdout {
self.inner.stdout(Stdio::piped());
}
if !self.stderr {
self.inner.stderr(Stdio::piped());
}
let child = Child::new(self);
async { child?.output().await }
}
}
impl From<std::process::Command> for Command {
fn from(inner: std::process::Command) -> Self {
Self {
inner,
stdin: false,
stdout: false,
stderr: false,
reap_on_drop: true,
kill_on_drop: false,
}
}
}
impl fmt::Debug for Command {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if f.alternate() {
f.debug_struct("Command")
.field("inner", &self.inner)
.field("stdin", &self.stdin)
.field("stdout", &self.stdout)
.field("stderr", &self.stderr)
.field("reap_on_drop", &self.reap_on_drop)
.field("kill_on_drop", &self.kill_on_drop)
.finish()
} else {
// Stdlib outputs command-line in Debug for Command. This does the
// same, if not in "alternate" (long pretty-printed) mode.
// This is useful for logs, for example.
fmt::Debug::fmt(&self.inner, f)
}
}
}
/// Moves `Fd` out of non-blocking mode.
#[cfg(unix)]
fn blocking_fd(fd: rustix::fd::BorrowedFd<'_>) -> io::Result<()> {
cfg_if::cfg_if! {
// ioctl(FIONBIO) sets the flag atomically, but we use this only on Linux
// for now, as with the standard library, because it seems to behave
// differently depending on the platform.
// https://github.com/rust-lang/rust/commit/efeb42be2837842d1beb47b51bb693c7474aba3d
// https://github.com/libuv/libuv/blob/e9d91fccfc3e5ff772d5da90e1c4a24061198ca0/src/unix/poll.c#L78-L80
// https://github.com/tokio-rs/mio/commit/0db49f6d5caf54b12176821363d154384357e70a
if #[cfg(target_os = "linux")] {
rustix::io::ioctl_fionbio(fd, false)?;
} else {
let previous = rustix::fs::fcntl_getfl(fd)?;
let new = previous & !rustix::fs::OFlags::NONBLOCK;
if new != previous {
rustix::fs::fcntl_setfl(fd, new)?;
}
}
}
Ok(())
}
struct CallOnDrop<F: FnMut()>(F);
impl<F: FnMut()> Drop for CallOnDrop<F> {
fn drop(&mut self) {
(self.0)();
}
}
#[cfg(test)]
mod test {
#[test]
fn polled_driver() {
use super::{driver, Command};
use futures_lite::future;
use futures_lite::prelude::*;
let is_thread_spawned =
|| super::DRIVER_THREAD_SPAWNED.load(std::sync::atomic::Ordering::SeqCst);
#[cfg(unix)]
fn command() -> Command {
let mut cmd = Command::new("sh");
cmd.arg("-c").arg("echo hello");
cmd
}
#[cfg(windows)]
fn command() -> Command {
let mut cmd = Command::new("cmd");
cmd.arg("/C").arg("echo hello");
cmd
}
#[cfg(unix)]
const OUTPUT: &[u8] = b"hello\n";
#[cfg(windows)]
const OUTPUT: &[u8] = b"hello\r\n";
future::block_on(async {
// Thread should not be spawned off the bat.
assert!(!is_thread_spawned());
// Spawn a driver.
let mut driver1 = Box::pin(driver());
future::poll_once(&mut driver1).await;
assert!(!is_thread_spawned());
// We should be able to run the driver in parallel with a process future.
async {
(&mut driver1).await;
}
.or(async {
let output = command().output().await.unwrap();
assert_eq!(output.stdout, OUTPUT);
})
.await;
assert!(!is_thread_spawned());
// Spawn a second driver.
let mut driver2 = Box::pin(driver());
future::poll_once(&mut driver2).await;
assert!(!is_thread_spawned());
// Poll both drivers in parallel.
async {
(&mut driver1).await;
}
.or(async {
(&mut driver2).await;
})
.or(async {
let output = command().output().await.unwrap();
assert_eq!(output.stdout, OUTPUT);
})
.await;
assert!(!is_thread_spawned());
// Once one is dropped, the other should take over.
drop(driver1);
assert!(!is_thread_spawned());
// Poll driver2 in parallel with a process future.
async {
(&mut driver2).await;
}
.or(async {
let output = command().output().await.unwrap();
assert_eq!(output.stdout, OUTPUT);
})
.await;
assert!(!is_thread_spawned());
// Once driver2 is dropped, the thread should not be spawned, as there are no active
// child processes..
drop(driver2);
assert!(!is_thread_spawned());
// We should now be able to poll the process future independently, it will spawn the
// thread.
let output = command().output().await.unwrap();
assert_eq!(output.stdout, OUTPUT);
assert!(is_thread_spawned());
});
}
}
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