#process #command #group #session #pty

no-std process-wrap

Wrap a Command, to spawn processes in a group or session or job etc

5 stable releases

8.0.0 Apr 20, 2024
7.1.0 Apr 20, 2024
6.0.1 Mar 11, 2024
5.3.0 Mar 11, 2024

#127 in Operating systems

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1,668 downloads per month
Used in 5 crates (2 directly)

Apache-2.0 OR MIT

175KB
1.5K SLoC

Crate release version Crate license: Apache 2.0 or MIT CI status

process-wrap

  • API documentation.
  • Dual-licensed with Apache 2.0 and MIT.
  • Successor to command-group.
  • Minimum Supported Rust Version: 1.75.0.
    • Only the latest stable rustc version is supported.
    • MSRV increases will not incur major version bumps.

Unlike command-group, process-wrap doesn't implement a single cross-platform API. Instead, it provides composable wrappers which implement a single concern each. It is left to the developer to use the appropriate wrapper(s) for their use-case and platform.

As the successor to (and containing a lot of the code of) command-group, versioning starts at 6.0.0. You can think of it as a breaking change to command-group, though the paradigm is quite different. The full test suite from command-group was retained: process-wrap has parity on functionality as a starting point.

Quick start

[dependencies]
process-wrap = { version = "8.0.0", features = ["tokio1"] }

By default, the crate does nothing, you need to enable either the std or Tokio "frontend". A default set of wrappers are enabled; you may choose to only compile those you need, see the features list.

use tokio::process::Command;
use process_wrap::tokio::*;

let mut child = TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessGroup::leader())
  .spawn()?;
let status = Box::into_pin(child.wait()).await?;
dbg!(status);

or on Windows

use tokio::process::Command;
use process_wrap::tokio::*;

let mut child = TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(JobObject::new())
  .spawn()?;
let status = Box::into_pin(child.wait()).await?;
dbg!(status);

or with sessions

use tokio::process::Command;
use process_wrap::tokio::*;

let mut child = TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessSession)
  .spawn()?;
let status = Box::into_pin(child.wait()).await?;
dbg!(status);

or with multiple wrappers

use tokio::process::Command;
use process_wrap::tokio::*;

let mut child = TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessSession)
  .wrap(KillOnDrop)
  .spawn()?;
let status = Box::into_pin(child.wait()).await?;
dbg!(status);

or with std

[dependencies]
process-wrap = { version = "8.0.0", features = ["std"] }
use std::process::Command;
use process_wrap::std::*;

let mut child = StdCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessGroup::leader())
  .spawn()?;
let status = child.wait()?;
dbg!(status);

Wrappers

Job object

  • Platforms: Windows
  • Like command-group.
  • Feature: job-object (default)
TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(JobObject)
  .spawn()?;

Process group

  • Platforms: POSIX (Linux, Mac, BSDs...)
  • Like command-group >=5.0.0.
  • Feature: process-group (default)
TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessGroup::leader())
  .spawn()?;

Or join a different group instead:

TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessGroup::attach_to(pgid))
  .spawn()?;

For Windows process groups, use CreationFlags::NEW_PROCESS_GROUP and/or JobObject::new().

Process session

  • Platforms: POSIX (Linux, Mac, BSDs...)
  • Like command-group <5.0.0.
  • Feature: process-session (default)

This combines creating a new session and a new group, and setting this process as leader. To join the session from another process, use ProcessGroup::attach_to() instead.

TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ProcessSession)
  .spawn()?;

Reset signal mask

  • Platforms: POSIX (Linux, Mac, BSDs...)
  • Feature: reset-sigmask

This resets the signal mask of the process instead of inheriting it from the parent.

TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(ResetSigmask)
  .spawn()?;

Creation flags

  • Platforms: Windows
  • Like command-group.
  • Feature: creation-flags (default)

This is a shim to allow setting Windows process creation flags with this API, as otherwise they'd be overwritten.

use windows::Win32::System::Threading::*;
TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(CreationFlags(CREATE_NO_WINDOW | CREATE_DETACHED))
  .wrap(JobObject)
  .spawn()?;

Kill on drop

  • Platforms: all (Tokio-only)
  • Like command-group.
  • Feature: kill-on-drop (default)

This is a shim to allow wrappers to handle the kill-on-drop flag, as it can't be read from Command.

let child = TokioCommandWrap::with_new("watch", |command| { command.arg("ls"); })
  .wrap(KillOnDrop)
  .wrap(ProcessGroup::leader())
  .spawn()?;
drop(child);

Your own

Implementing a wrapper is done via a set of traits. The std and Tokio sides are completely separate, due to the different underlying APIs. Of course you can (and should) re-use/share code wherever possible if implementing both.

At minimum, you must implement StdCommandWrapper and/or TokioCommandWrapper. These provide the same functionality, but differ in the exact types specified. Here's the most basic impl (shown for Tokio):

#[derive(Debug)]
pub struct YourWrapper;
impl TokioCommandWrapper for YourWrapper {}

That's right, all member methods are optional. The trait provides extension or hook points into the lifecycle of a Command:

  • fn extend(&mut self, other: Box<dyn TokioCommandWrapper>) is called if .wrap(YourWrapper) is done twice. Only one of a wrapper type can exist, so this gives the opportunity to incorporate all or part of the second wrapper instance into the first. By default, this does nothing (ie only the first registered wrapper instance of a type does anything).

  • fn pre_spawn(&mut self, command: &mut Command, core: &TokioCommandWrap) is called before the command is spawned, and gives mutable access to it. It also gives mutable access to the wrapper instance, so state can be stored if needed. The core reference gives access to data from other wrappers; for example, that's how CreationFlags on Windows works along with JobObject. Noop by default.

  • fn post_spawn(&mut self, child: &mut tokio::process::Child, core: &TokioCommandWrap) is called after spawn, and should be used for any necessary cleanups. It is offered for completedness but is expected to be less used than wrap_child(). Noop by default.

  • fn wrap_child(&mut self, child: Box<dyn TokioChildWrapper>, core: &TokioCommandWrap) is called after all post_spawn()s have run. If your wrapper needs to override the methods on Child, then it should create an instance of its own type implementing TokioChildWrapper and return it here. Child wraps are in order: you may end up with a Foo(Bar(Child)) or a Bar(Foo(Child)) depending on if .wrap(Foo).wrap(Bar) or .wrap(Bar).wrap(Foo) was called. If your functionality is order-dependent, make sure to specify so in your documentation! Default is noop: no wrapping is performed and the input child is returned as-is.

Refer to the API documentation for more detail and the specifics of child wrapper traits.

Features

Frontends

  • std: enables the std-based API.
  • tokio1: enables the Tokio-based API.

Both can exist at the same time, but generally you should use one or the other.

Wrappers

Dependencies

~2–45MB
~679K SLoC