vendor/tokio-process/src/lib.rs

//! An implementation of asynchronous process management for Tokio.
//!
//! This crate provides a `CommandExt` trait to enhance the functionality of the
//! `Command` type in the standard library. The three methods provided by this
//! trait mirror the "spawning" methods in the standard library. The
//! `CommandExt` trait in this crate, though, returns "future aware" types that
//! interoperate with Tokio. The asynchronous process support is provided
//! through signal handling on Unix and system APIs on Windows.
//!
//! # Examples
//!
//! Here's an example program which will spawn `echo hello world` and then wait
//! for it using an event loop.
//!
//! ```no_run
//! extern crate futures;
//! extern crate tokio;
//! extern crate tokio_process;
//!
//! use std::process::Command;
//!
//! use futures::Future;
//! use tokio_process::CommandExt;
//!
//! fn main() {
//!     // Use the standard library's `Command` type to build a process and
//!     // then execute it via the `CommandExt` trait.
//!     let child = Command::new("echo").arg("hello").arg("world")
//!                         .spawn_async();
//!
//!     // Make sure our child succeeded in spawning and process the result
//!     let future = child.expect("failed to spawn")
//!         .map(|status| println!("exit status: {}", status))
//!         .map_err(|e| panic!("failed to wait for exit: {}", e));
//!
//!     // Send the future to the tokio runtime for execution
//!     tokio::run(future)
//! }
//! ```
//!
//! Next, let's take a look at an example where we not only spawn `echo hello
//! world` but we also capture its output.
//!
//! ```no_run
//! extern crate futures;
//! extern crate tokio;
//! extern crate tokio_process;
//!
//! use std::process::Command;
//!
//! use futures::Future;
//! use tokio_process::CommandExt;
//!
//! fn main() {
//!     // Like above, but use `output_async` which returns a future instead of
//!     // immediately returning the `Child`.
//!     let output = Command::new("echo").arg("hello").arg("world")
//!                         .output_async();
//!
//!     let future = output.map_err(|e| panic!("failed to collect output: {}", e))
//!         .map(|output| {
//!             assert!(output.status.success());
//!             assert_eq!(output.stdout, b"hello world\n");
//!         });
//!
//!     tokio::run(future);
//! }
//! ```
//!
//! We can also read input line by line.
//!
//! ```no_run
//! extern crate futures;
//! extern crate tokio;
//! extern crate tokio_process;
//! extern crate tokio_io;
//!
//! use std::io;
//! use std::process::{Command, Stdio};
//!
//! use futures::{Future, Stream};
//! use tokio_process::{CommandExt, Child};
//!
//! fn print_lines(mut cat: Child) -> Box<Future<Item = (), Error = ()> + Send + 'static> {
//!     let stdout = cat.stdout().take().unwrap();
//!     let reader = io::BufReader::new(stdout);
//!     let lines = tokio_io::io::lines(reader);
//!     let cycle = lines.for_each(|l| {
//!         println!("Line: {}", l);
//!         Ok(())
//!     });
//!
//!     let future = cycle.join(cat)
//!         .map(|_| ())
//!         .map_err(|e| panic!("{}", e));
//!
//!     Box::new(future)
//! }
//!
//! fn main() {
//!     let mut cmd = Command::new("cat");
//!     cmd.stdout(Stdio::piped());
//!
//!     let future = print_lines(cmd.spawn_async().expect("failed to spawn command"));
//!     tokio::run(future);
//! }
//! ```
//!
//! # Caveats
//!
//! While similar to the standard library, this crate's `Child` type differs
//! importantly in the behavior of `drop`. In the standard library, a child
//! process will continue running after the instance of `std::process::Child`
//! is dropped. In this crate, however, because `tokio_process::Child` is a
//! future of the child's `ExitStatus`, a child process is terminated if
//! `tokio_process::Child` is dropped. The behavior of the standard library can
//! be regained with the `Child::forget` method.

#![warn(missing_debug_implementations)]
#![deny(missing_docs)]
#![doc(html_root_url = "https://docs.rs/tokio-process/0.2")]

extern crate futures;
extern crate tokio_io;
extern crate tokio_reactor;
extern crate mio;

use std::io::{self, Read, Write};
use std::process::{self, ExitStatus, Output, Stdio};

use futures::{Future, Poll, IntoFuture};
use futures::future::{Either, ok};
use std::fmt;
use tokio_io::io::{read_to_end};
use tokio_io::{AsyncWrite, AsyncRead, IoFuture};
use tokio_reactor::Handle;

#[path = "unix.rs"]
#[cfg(unix)]
mod imp;

#[path = "windows.rs"]
#[cfg(windows)]
mod imp;

/// Extensions provided by this crate to the `Command` type in the standard
/// library.
///
/// This crate primarily enhances the standard library's `Command` type with
/// asynchronous capabilities. The currently three blocking functions in the
/// standard library, `spawn`, `status`, and `output`, all have asynchronous
/// versions through this trait.
///
/// Note that the `Child` type spawned is specific to this crate, and that the
/// I/O handles created from this crate are all asynchronous as well (differing
/// from their `std` counterparts).
pub trait CommandExt {
    /// Executes the command as a child process, returning a handle to it.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    ///
    /// This method will spawn the child process synchronously and return a
    /// handle to a future-aware child process. The `Child` returned implements
    /// `Future` itself to acquire the `ExitStatus` of the child, and otherwise
    /// the `Child` has methods to acquire handles to the stdin, stdout, and
    /// stderr streams.
    ///
    /// All I/O this child does will be associated with the current default
    /// event loop.
    fn spawn_async(&mut self) -> io::Result<Child> {
        self.spawn_async_with_handle(&Handle::default())
    }

    /// Executes the command as a child process, returning a handle to it.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    ///
    /// This method will spawn the child process synchronously and return a
    /// handle to a future-aware child process. The `Child` returned implements
    /// `Future` itself to acquire the `ExitStatus` of the child, and otherwise
    /// the `Child` has methods to acquire handles to the stdin, stdout, and
    /// stderr streams.
    ///
    /// The `handle` specified to this method must be a handle to a valid event
    /// loop, and all I/O this child does will be associated with the specified
    /// event loop.
    fn spawn_async_with_handle(&mut self, handle: &Handle) -> io::Result<Child>;

    /// Executes a command as a child process, waiting for it to finish and
    /// collecting its exit status.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    ///
    /// The `StatusAsync` future returned will resolve to the `ExitStatus`
    /// type in the standard library representing how the process exited. If
    /// any input/output handles are set to a pipe then they will be immediately
    ///  closed after the child is spawned.
    ///
    /// All I/O this child does will be associated with the current default
    /// event loop.
    ///
    /// If the `StatusAsync` future is dropped before the future resolves, then
    /// the child will be killed, if it was spawned.
    ///
    /// # Errors
    ///
    /// This function will return an error immediately if the child process
    /// cannot be spawned. Otherwise errors obtained while waiting for the child
    /// are returned through the `StatusAsync` future.
    fn status_async(&mut self) -> io::Result<StatusAsync> {
        self.status_async_with_handle(&Handle::default())
    }

    /// Executes a command as a child process, waiting for it to finish and
    /// collecting its exit status.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    ///
    /// The `StatusAsync` future returned will resolve to the `ExitStatus`
    /// type in the standard library representing how the process exited. If
    /// any input/output handles are set to a pipe then they will be immediately
    ///  closed after the child is spawned.
    ///
    /// The `handle` specified must be a handle to a valid event loop, and all
    /// I/O this child does will be associated with the specified event loop.
    ///
    /// If the `StatusAsync` future is dropped before the future resolves, then
    /// the child will be killed, if it was spawned.
    ///
    /// # Errors
    ///
    /// This function will return an error immediately if the child process
    /// cannot be spawned. Otherwise errors obtained while waiting for the child
    /// are returned through the `StatusAsync` future.
    fn status_async_with_handle(&mut self, handle: &Handle) -> io::Result<StatusAsync>;

    /// Executes the command as a child process, waiting for it to finish and
    /// collecting all of its output.
    ///
    /// > **Note**: this method, unlike the standard library, will
    /// > unconditionally configure the stdout/stderr handles to be pipes, even
    /// > if they have been previously configured. If this is not desired then
    /// > the `spawn_async` method should be used in combination with the
    /// > `wait_with_output` method on child.
    ///
    /// This method will return a future representing the collection of the
    /// child process's stdout/stderr. The `OutputAsync` future will resolve to
    /// the `Output` type in the standard library, containing `stdout` and
    /// `stderr` as `Vec<u8>` along with an `ExitStatus` representing how the
    /// process exited.
    ///
    /// All I/O this child does will be associated with the current default
    /// event loop.
    ///
    /// If the `OutputAsync` future is dropped before the future resolves, then
    /// the child will be killed, if it was spawned.
    fn output_async(&mut self) -> OutputAsync {
        self.output_async_with_handle(&Handle::default())
    }

    /// Executes the command as a child process, waiting for it to finish and
    /// collecting all of its output.
    ///
    /// > **Note**: this method, unlike the standard library, will
    /// > unconditionally configure the stdout/stderr handles to be pipes, even
    /// > if they have been previously configured. If this is not desired then
    /// > the `spawn_async` method should be used in combination with the
    /// > `wait_with_output` method on child.
    ///
    /// This method will return a future representing the collection of the
    /// child process's stdout/stderr. The `OutputAsync` future will resolve to
    /// the `Output` type in the standard library, containing `stdout` and
    /// `stderr` as `Vec<u8>` along with an `ExitStatus` representing how the
    /// process exited.
    ///
    /// The `handle` specified must be a handle to a valid event loop, and all
    /// I/O this child does will be associated with the specified event loop.
    ///
    /// If the `OutputAsync` future is dropped before the future resolves, then
    /// the child will be killed, if it was spawned.
    fn output_async_with_handle(&mut self, handle: &Handle) -> OutputAsync;
}


impl CommandExt for process::Command {
    fn spawn_async_with_handle(&mut self, handle: &Handle) -> io::Result<Child> {
        let mut child = Child {
            child: imp::Child::new(try!(self.spawn()), handle),
            stdin: None,
            stdout: None,
            stderr: None,
            kill_on_drop: true,
        };
        child.stdin = try!(child.child.register_stdin(handle)).map(|io| {
            ChildStdin { inner: io }
        });
        child.stdout = try!(child.child.register_stdout(handle)).map(|io| {
            ChildStdout { inner: io }
        });
        child.stderr = try!(child.child.register_stderr(handle)).map(|io| {
            ChildStderr { inner: io }
        });
        Ok(child)
    }

    fn status_async_with_handle(&mut self, handle: &Handle) -> io::Result<StatusAsync> {
        self.spawn_async_with_handle(handle).map(|mut child| {
            // Ensure we close any stdio handles so we can't deadlock
            // waiting on the child which may be waiting to read/write
            // to a pipe we're holding.
            child.stdin.take();
            child.stdout.take();
            child.stderr.take();

            StatusAsync {
                inner: child,
            }
        })
    }

    fn output_async_with_handle(&mut self, handle: &Handle) -> OutputAsync {
        self.stdout(Stdio::piped());
        self.stderr(Stdio::piped());

        let inner = self.spawn_async_with_handle(handle)
            .into_future()
            .and_then(|c| c.wait_with_output());

        OutputAsync {
            inner: Box::new(inner),
        }
    }
}

/// Representation of a child process spawned onto an event loop.
///
/// This type is also a future which will yield the `ExitStatus` of the
/// underlying child process. A `Child` here also provides access to information
/// like the OS-assigned identifier and the stdio streams.
///
/// > **Note**: The behavior of `drop` on a child in this crate is *different
/// > than the behavior of the standard library*. If a `tokio_process::Child` is
/// > dropped before the process finishes then the process will be terminated.
/// > In the standard library, however, the process continues executing. This is
/// > done because futures in general take `drop` as a sign of cancellation, and
/// > this `Child` is itself a future. If you'd like to run a process in the
/// > background, though, you may use the `forget` method.
#[must_use = "futures do nothing unless polled"]
#[derive(Debug)]
pub struct Child {
    child: imp::Child,
    kill_on_drop: bool,
    stdin: Option<ChildStdin>,
    stdout: Option<ChildStdout>,
    stderr: Option<ChildStderr>,
}

impl Child {
    /// Returns the OS-assigned process identifier associated with this child.
    pub fn id(&self) -> u32 {
        self.child.id()
    }

    /// Forces the child to exit.
    ///
    /// This is equivalent to sending a SIGKILL on unix platforms.
    pub fn kill(&mut self) -> io::Result<()> {
        self.child.kill()
    }

    /// Returns a handle for writing to the child's stdin, if it has been
    /// captured
    pub fn stdin(&mut self) -> &mut Option<ChildStdin> {
        &mut self.stdin
    }

    /// Returns a handle for writing to the child's stdout, if it has been
    /// captured
    pub fn stdout(&mut self) -> &mut Option<ChildStdout> {
        &mut self.stdout
    }

    /// Returns a handle for writing to the child's stderr, if it has been
    /// captured
    pub fn stderr(&mut self) -> &mut Option<ChildStderr> {
        &mut self.stderr
    }

    /// Returns a future that will resolve to an `Output`, containing the exit
    /// status, stdout, and stderr of the child process.
    ///
    /// The returned future will simultaneously waits for the child to exit and
    /// collect all remaining output on the stdout/stderr handles, returning an
    /// `Output` instance.
    ///
    /// The stdin handle to the child process, if any, will be closed before
    /// waiting. This helps avoid deadlock: it ensures that the child does not
    /// block waiting for input from the parent, while the parent waits for the
    /// child to exit.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent. In
    /// order to capture the output into this `Output` it is necessary to create
    /// new pipes between parent and child. Use `stdout(Stdio::piped())` or
    /// `stderr(Stdio::piped())`, respectively, when creating a `Command`.
    pub fn wait_with_output(mut self) -> WaitWithOutput {
        drop(self.stdin().take());
        let stdout = match self.stdout().take() {
            Some(io) => Either::A(read_to_end(io, Vec::new()).map(|p| p.1)),
            None => Either::B(ok(Vec::new())),
        };
        let stderr = match self.stderr().take() {
            Some(io) => Either::A(read_to_end(io, Vec::new()).map(|p| p.1)),
            None => Either::B(ok(Vec::new())),
        };

        WaitWithOutput {
            inner: Box::new(self.join3(stdout, stderr).map(|(status, stdout, stderr)| {
                Output {
                    status: status,
                    stdout: stdout,
                    stderr: stderr,
                }
            }))
        }
    }

    /// Drop this `Child` without killing the underlying process.
    ///
    /// Normally a `Child` is killed if it's still alive when dropped, but this
    /// method will ensure that the child may continue running once the `Child`
    /// instance is dropped.
    ///
    /// > **Note**: this method may leak OS resources depending on your platform.
    /// > To ensure resources are eventually cleaned up, consider sending the
    /// > `Child` instance into an event loop as an alternative to this method.
    ///
    /// ```no_run
    /// # extern crate futures;
    /// # extern crate tokio;
    /// # extern crate tokio_process;
    /// #
    /// # use std::process::Command;
    /// #
    /// # use futures::Future;
    /// # use tokio_process::CommandExt;
    /// #
    /// # fn main() {
    /// let child = Command::new("echo").arg("hello").arg("world")
    ///                     .spawn_async()
    ///                     .expect("failed to spawn");
    ///
    /// let do_cleanup = child.map(|_| ()) // Ignore result
    ///                       .map_err(|_| ()); // Ignore errors
    ///
    /// tokio::spawn(do_cleanup);
    /// # }
    /// ```
    pub fn forget(mut self) {
        self.kill_on_drop = false;
    }
}

impl Future for Child {
    type Item = ExitStatus;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<ExitStatus, io::Error> {
        self.child.poll_exit()
    }
}

impl Drop for Child {
    fn drop(&mut self) {
        if self.kill_on_drop {
            drop(self.kill());
        }
    }
}

/// Future returned from the `Child::wait_with_output` method.
///
/// This future will resolve to the standard library's `Output` type which
/// contains the exit status, stdout, and stderr of a child process.
#[must_use = "futures do nothing unless polled"]
pub struct WaitWithOutput {
    inner: IoFuture<Output>,
}

impl fmt::Debug for WaitWithOutput {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.debug_struct("WaitWithOutput")
            .field("inner", &"..")
            .finish()
    }
}

impl Future for WaitWithOutput {
    type Item = Output;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<Output, io::Error> {
        self.inner.poll()
    }
}

#[doc(hidden)]
#[deprecated(note = "renamed to `StatusAsync`", since = "0.2.1")]
pub type StatusAsync2 = StatusAsync;

/// Future returned by the `CommandExt::status_async` method.
///
/// This future is used to conveniently spawn a child and simply wait for its
/// exit status. This future will resolves to the `ExitStatus` type in the
/// standard library.
#[must_use = "futures do nothing unless polled"]
#[derive(Debug)]
pub struct StatusAsync {
    inner: Child,
}

impl Future for StatusAsync {
    type Item = ExitStatus;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<ExitStatus, io::Error> {
        self.inner.poll()
    }
}

/// Future returned by the `CommandExt::output_async` method.
///
/// This future is mostly equivalent to spawning a process and then calling
/// `wait_with_output` on it internally. This can be useful to simply spawn a
/// process, collecting all of its output and its exit status.
#[must_use = "futures do nothing unless polled"]
pub struct OutputAsync {
    inner: IoFuture<Output>,
}

impl fmt::Debug for OutputAsync {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.debug_struct("OutputAsync")
            .field("inner", &"..")
            .finish()
    }
}

impl Future for OutputAsync {
    type Item = Output;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<Output, io::Error> {
        self.inner.poll()
    }
}

/// The standard input stream for spawned children.
///
/// This type implements the `Write` trait to pass data to the stdin handle of
/// a child process. Note that this type is also "futures aware" meaning that it
/// is both (a) nonblocking and (b) will panic if used off of a future's task.
#[derive(Debug)]
pub struct ChildStdin {
    inner: imp::ChildStdin,
}

/// The standard output stream for spawned children.
///
/// This type implements the `Read` trait to read data from the stdout handle
/// of a child process. Note that this type is also "futures aware" meaning
/// that it is both (a) nonblocking and (b) will panic if used off of a
/// future's task.
#[derive(Debug)]
pub struct ChildStdout {
    inner: imp::ChildStdout,
}

/// The standard error stream for spawned children.
///
/// This type implements the `Read` trait to read data from the stderr handle
/// of a child process. Note that this type is also "futures aware" meaning
/// that it is both (a) nonblocking and (b) will panic if used off of a
/// future's task.
#[derive(Debug)]
pub struct ChildStderr {
    inner: imp::ChildStderr,
}

impl Write for ChildStdin {
    fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
        self.inner.write(bytes)
    }

    fn flush(&mut self) -> io::Result<()> {
        self.inner.flush()
    }
}

impl AsyncWrite for ChildStdin {
    fn shutdown(&mut self) -> Poll<(), io::Error> {
        self.inner.shutdown()
    }
}

impl Read for ChildStdout {
    fn read(&mut self, bytes: &mut [u8]) -> io::Result<usize> {
        self.inner.read(bytes)
    }
}

impl AsyncRead for ChildStdout {
}

impl Read for ChildStderr {
    fn read(&mut self, bytes: &mut [u8]) -> io::Result<usize> {
        self.inner.read(bytes)
    }
}

impl AsyncRead for ChildStderr {
}

#[cfg(unix)]
mod sys {
    use std::os::unix::io::{AsRawFd, RawFd};
    use super::{ChildStdin, ChildStdout, ChildStderr};

    impl AsRawFd for ChildStdin {
        fn as_raw_fd(&self) -> RawFd {
            self.inner.get_ref().as_raw_fd()
        }
    }

    impl AsRawFd for ChildStdout {
        fn as_raw_fd(&self) -> RawFd {
            self.inner.get_ref().as_raw_fd()
        }
    }

    impl AsRawFd for ChildStderr {
        fn as_raw_fd(&self) -> RawFd {
            self.inner.get_ref().as_raw_fd()
        }
    }
}

#[cfg(windows)]
mod sys {
    use std::os::windows::io::{AsRawHandle, RawHandle};
    use super::{ChildStdin, ChildStdout, ChildStderr};

    impl AsRawHandle for ChildStdin {
        fn as_raw_handle(&self) -> RawHandle {
            self.inner.get_ref().as_raw_handle()
        }
    }

    impl AsRawHandle for ChildStdout {
        fn as_raw_handle(&self) -> RawHandle {
            self.inner.get_ref().as_raw_handle()
        }
    }

    impl AsRawHandle for ChildStderr {
        fn as_raw_handle(&self) -> RawHandle {
            self.inner.get_ref().as_raw_handle()
        }
    }
}