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diff --git a/library/std/src/sys/unix/ext/process.rs b/library/std/src/sys/unix/ext/process.rs
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+//! Unix-specific extensions to primitives in the `std::process` module.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use crate::ffi::OsStr;
+use crate::io;
+use crate::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+use crate::process;
+use crate::sys;
+use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
+
+/// Unix-specific extensions to the [`process::Command`] builder.
+///
+/// [`process::Command`]: ../../../../std/process/struct.Command.html
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait CommandExt {
+    /// Sets the child process's user ID. This translates to a
+    /// `setuid` call in the child process. Failure in the `setuid`
+    /// call will cause the spawn to fail.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn uid(&mut self, id: u32) -> &mut process::Command;
+
+    /// Similar to `uid`, but sets the group ID of the child process. This has
+    /// the same semantics as the `uid` field.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn gid(&mut self, id: u32) -> &mut process::Command;
+
+    /// Schedules a closure to be run just before the `exec` function is
+    /// invoked.
+    ///
+    /// The closure is allowed to return an I/O error whose OS error code will
+    /// be communicated back to the parent and returned as an error from when
+    /// the spawn was requested.
+    ///
+    /// Multiple closures can be registered and they will be called in order of
+    /// their registration. If a closure returns `Err` then no further closures
+    /// will be called and the spawn operation will immediately return with a
+    /// failure.
+    ///
+    /// # Notes and Safety
+    ///
+    /// This closure will be run in the context of the child process after a
+    /// `fork`. This primarily means that any modifications made to memory on
+    /// behalf of this closure will **not** be visible to the parent process.
+    /// This is often a very constrained environment where normal operations
+    /// like `malloc` or acquiring a mutex are not guaranteed to work (due to
+    /// other threads perhaps still running when the `fork` was run).
+    ///
+    /// This also means that all resources such as file descriptors and
+    /// memory-mapped regions got duplicated. It is your responsibility to make
+    /// sure that the closure does not violate library invariants by making
+    /// invalid use of these duplicates.
+    ///
+    /// When this closure is run, aspects such as the stdio file descriptors and
+    /// working directory have successfully been changed, so output to these
+    /// locations may not appear where intended.
+    #[stable(feature = "process_pre_exec", since = "1.34.0")]
+    unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
+    where
+        F: FnMut() -> io::Result<()> + Send + Sync + 'static;
+
+    /// Schedules a closure to be run just before the `exec` function is
+    /// invoked.
+    ///
+    /// This method is stable and usable, but it should be unsafe. To fix
+    /// that, it got deprecated in favor of the unsafe [`pre_exec`].
+    ///
+    /// [`pre_exec`]: #tymethod.pre_exec
+    #[stable(feature = "process_exec", since = "1.15.0")]
+    #[rustc_deprecated(since = "1.37.0", reason = "should be unsafe, use `pre_exec` instead")]
+    fn before_exec<F>(&mut self, f: F) -> &mut process::Command
+    where
+        F: FnMut() -> io::Result<()> + Send + Sync + 'static,
+    {
+        unsafe { self.pre_exec(f) }
+    }
+
+    /// Performs all the required setup by this `Command`, followed by calling
+    /// the `execvp` syscall.
+    ///
+    /// On success this function will not return, and otherwise it will return
+    /// an error indicating why the exec (or another part of the setup of the
+    /// `Command`) failed.
+    ///
+    /// `exec` not returning has the same implications as calling
+    /// [`process::exit`] – no destructors on the current stack or any other
+    /// thread’s stack will be run. Therefore, it is recommended to only call
+    /// `exec` at a point where it is fine to not run any destructors. Note,
+    /// that the `execvp` syscall independently guarantees that all memory is
+    /// freed and all file descriptors with the `CLOEXEC` option (set by default
+    /// on all file descriptors opened by the standard library) are closed.
+    ///
+    /// This function, unlike `spawn`, will **not** `fork` the process to create
+    /// a new child. Like spawn, however, the default behavior for the stdio
+    /// descriptors will be to inherited from the current process.
+    ///
+    /// [`process::exit`]: ../../../process/fn.exit.html
+    ///
+    /// # Notes
+    ///
+    /// The process may be in a "broken state" if this function returns in
+    /// error. For example the working directory, environment variables, signal
+    /// handling settings, various user/group information, or aspects of stdio
+    /// file descriptors may have changed. If a "transactional spawn" is
+    /// required to gracefully handle errors it is recommended to use the
+    /// cross-platform `spawn` instead.
+    #[stable(feature = "process_exec2", since = "1.9.0")]
+    fn exec(&mut self) -> io::Error;
+
+    /// Set executable argument
+    ///
+    /// Set the first process argument, `argv[0]`, to something other than the
+    /// default executable path.
+    #[stable(feature = "process_set_argv0", since = "1.45.0")]
+    fn arg0<S>(&mut self, arg: S) -> &mut process::Command
+    where
+        S: AsRef<OsStr>;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl CommandExt for process::Command {
+    fn uid(&mut self, id: u32) -> &mut process::Command {
+        self.as_inner_mut().uid(id);
+        self
+    }
+
+    fn gid(&mut self, id: u32) -> &mut process::Command {
+        self.as_inner_mut().gid(id);
+        self
+    }
+
+    unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
+    where
+        F: FnMut() -> io::Result<()> + Send + Sync + 'static,
+    {
+        self.as_inner_mut().pre_exec(Box::new(f));
+        self
+    }
+
+    fn exec(&mut self) -> io::Error {
+        self.as_inner_mut().exec(sys::process::Stdio::Inherit)
+    }
+
+    fn arg0<S>(&mut self, arg: S) -> &mut process::Command
+    where
+        S: AsRef<OsStr>,
+    {
+        self.as_inner_mut().set_arg_0(arg.as_ref());
+        self
+    }
+}
+
+/// Unix-specific extensions to [`process::ExitStatus`].
+///
+/// [`process::ExitStatus`]: ../../../../std/process/struct.ExitStatus.html
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ExitStatusExt {
+    /// Creates a new `ExitStatus` from the raw underlying `i32` return value of
+    /// a process.
+    #[stable(feature = "exit_status_from", since = "1.12.0")]
+    fn from_raw(raw: i32) -> Self;
+
+    /// If the process was terminated by a signal, returns that signal.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn signal(&self) -> Option<i32>;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ExitStatusExt for process::ExitStatus {
+    fn from_raw(raw: i32) -> Self {
+        process::ExitStatus::from_inner(From::from(raw))
+    }
+
+    fn signal(&self) -> Option<i32> {
+        self.as_inner().signal()
+    }
+}
+
+#[stable(feature = "process_extensions", since = "1.2.0")]
+impl FromRawFd for process::Stdio {
+    unsafe fn from_raw_fd(fd: RawFd) -> process::Stdio {
+        let fd = sys::fd::FileDesc::new(fd);
+        let io = sys::process::Stdio::Fd(fd);
+        process::Stdio::from_inner(io)
+    }
+}
+
+#[stable(feature = "process_extensions", since = "1.2.0")]
+impl AsRawFd for process::ChildStdin {
+    fn as_raw_fd(&self) -> RawFd {
+        self.as_inner().fd().raw()
+    }
+}
+
+#[stable(feature = "process_extensions", since = "1.2.0")]
+impl AsRawFd for process::ChildStdout {
+    fn as_raw_fd(&self) -> RawFd {
+        self.as_inner().fd().raw()
+    }
+}
+
+#[stable(feature = "process_extensions", since = "1.2.0")]
+impl AsRawFd for process::ChildStderr {
+    fn as_raw_fd(&self) -> RawFd {
+        self.as_inner().fd().raw()
+    }
+}
+
+#[stable(feature = "into_raw_os", since = "1.4.0")]
+impl IntoRawFd for process::ChildStdin {
+    fn into_raw_fd(self) -> RawFd {
+        self.into_inner().into_fd().into_raw()
+    }
+}
+
+#[stable(feature = "into_raw_os", since = "1.4.0")]
+impl IntoRawFd for process::ChildStdout {
+    fn into_raw_fd(self) -> RawFd {
+        self.into_inner().into_fd().into_raw()
+    }
+}
+
+#[stable(feature = "into_raw_os", since = "1.4.0")]
+impl IntoRawFd for process::ChildStderr {
+    fn into_raw_fd(self) -> RawFd {
+        self.into_inner().into_fd().into_raw()
+    }
+}
+
+/// Returns the OS-assigned process identifier associated with this process's parent.
+#[stable(feature = "unix_ppid", since = "1.27.0")]
+pub fn parent_id() -> u32 {
+    crate::sys::os::getppid()
+}