Struct command_group::AsyncGroupChild

pub struct AsyncGroupChild { /* private fields */ }

Representation of a running or exited child process group (Tokio variant).

This wraps Tokio’s Child type with methods that work with process groups.

Examples

use tokio::process::Command;
use command_group::AsyncCommandGroup;

let mut child = Command::new("/bin/cat")
                        .arg("file.txt")
                        .group_spawn()
                        .expect("failed to execute child");

let ecode = child.wait()
                 .await
                 .expect("failed to wait on child");

assert!(ecode.success());

Implementations

impl AsyncGroupChild

pub fn inner(&mut self) -> &mut Child

Returns the stdlib Child object.

Note that the inner child may not be in the same state as this output child, due to how methods like wait and kill are implemented. It is not recommended to use this method after using any of the other methods on this struct.

Examples

Reading from stdout:

use std::process::Stdio;
use tokio::{io::AsyncReadExt, process::Command};
use command_group::AsyncCommandGroup;

let mut child = Command::new("ls").stdout(Stdio::piped()).group_spawn().expect("ls command didn't start");
let mut output = String::new();
if let Some(mut out) = child.inner().stdout.take() {
    out.read_to_string(&mut output).await.expect("failed to read from child");
}
println!("output: {}", output);

pub fn into_inner(self) -> Child

Consumes itself and returns the stdlib Child object.

Note that the inner child may not be in the same state as this output child, due to how methods like wait and kill are implemented. It is not recommended to use this method after using any of the other methods on this struct.

On Windows, this unnavoidably leaves a handle unclosed. Prefer inner().

Examples

Writing to input:

use std::process::Stdio;
use tokio::{io::AsyncWriteExt, process::Command};
use command_group::AsyncCommandGroup;

let mut child = Command::new("cat").stdin(Stdio::piped()).group_spawn().expect("cat command didn't start");
if let Some(mut din) = child.into_inner().stdin.take() {
     din.write_all(b"Woohoo!").await.expect("failed to write");
}

pub async fn kill(&mut self) -> Result<()>

Forces the child process group to exit.

If the group has already exited, an InvalidInput error is returned.

This is equivalent to sending a SIGKILL on Unix platforms.

See the Tokio documentation for more.

Examples

Basic usage:

use tokio::process::Command;
use command_group::AsyncCommandGroup;

let mut command = Command::new("yes");
if let Ok(mut child) = command.group_spawn() {
    child.kill().await.expect("command wasn't running");
} else {
    println!("yes command didn't start");
}

pub fn start_kill(&mut self) -> Result<()>

Attempts to force the child to exit, but does not wait for the request to take effect.

This is equivalent to sending a SIGKILL on Unix platforms.

Note that on Unix platforms it is possible for a zombie process to remain after a kill is sent; to avoid this, the caller should ensure that either child.wait().await or child.try_wait() is invoked successfully.

See the Tokio documentation for more.

pub fn id(&self) -> Option<u32>

Returns the OS-assigned process group identifier.

Like Tokio, this returns None if the child process group has alread exited, to avoid holding onto an expired (and possibly reused) PGID.

See the Tokio documentation for more.

Examples

Basic usage:

use tokio::process::Command;
use command_group::AsyncCommandGroup;

let mut command = Command::new("ls");
if let Ok(child) = command.group_spawn() {
    if let Some(pgid) = child.id() {
        println!("Child group's ID is {}", pgid);
    } else {
        println!("Child group is gone");
    }
} else {
    println!("ls command didn't start");
}

pub async fn wait(&mut self) -> Result<ExitStatus>

Waits for the child group to exit completely, returning the status that the process leader exited with.

See the Tokio documentation for more.

The current implementation spawns a blocking task on the Tokio thread pool; contributions are welcome for a better version.

An important consideration on Unix platforms is that there is no way to cancel the wait syscall. Cancelling this future will not cancel that underlying wait call. That has consequences: a waited process that exits will have its resources cleaned up by the kernel. If the application is no longer listening for that wait returning, it will not know that the process has been cleaned up, and will try to wait on it again. That in turn may fail, or could even attach to a recycled PID which would then point to a completely different process.

Examples

Basic usage:

use tokio::process::Command;
use command_group::AsyncCommandGroup;

let mut command = Command::new("ls");
if let Ok(mut child) = command.group_spawn() {
    child.wait().await.expect("command wasn't running");
    println!("Child has finished its execution!");
} else {
    println!("ls command didn't start");
}

pub fn try_wait(&mut self) -> Result<Option<ExitStatus>>

Attempts to collect the exit status of the child if it has already exited.

See the Tokio documentation for more.

Examples

Basic usage:

use tokio::process::Command;
use command_group::AsyncCommandGroup;

let mut child = Command::new("ls").group_spawn().unwrap();

match child.try_wait() {
    Ok(Some(status)) => println!("exited with: {}", status),
    Ok(None) => {
        println!("status not ready yet, let's really wait");
        let res = child.wait().await;
        println!("result: {:?}", res);
    }
    Err(e) => println!("error attempting to wait: {}", e),
}

pub async fn wait_with_output(self) -> Result<Output>

Simultaneously waits for the child to exit and collect all remaining output on the stdout/stderr handles, returning an Output instance.

See the Tokio documentation for more.

Examples

Basic usage:

use std::process::Stdio;
use tokio::process::Command;
use command_group::AsyncCommandGroup;

let child = Command::new("/bin/cat")
    .arg("file.txt")
    .stdout(Stdio::piped())
    .group_spawn()
    .expect("failed to execute child");

let output = child
    .wait_with_output()
    .await
    .expect("failed to wait on child");

assert!(output.status.success());

Trait Implementations

impl Debug for AsyncGroupChild

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.