Add std::process

Per [RFC 579](https://github.com/rust-lang/rfcs/pull/579), this commit
adds a new `std::process` module. This module is largely based on the
existing `std::old_io::process` module, but refactors the API to use
`OsStr` and other new standards set out by IO reform.

The existing module is not yet deprecated, to allow for the new API to
get a bit of testing before a mass migration to it.

1 files changed, 834 insertions, 0 deletions

diff --git a/src/libstd/process.rs b/src/libstd/process.rs
new file mode 100644
index 00000000000..d2b98ec8939
--- /dev/null
+++ b/src/libstd/process.rs
@@ -0,0 +1,834 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Working with processes.
+
+#![unstable(feature = "process", reason = "recently added via RFC 579")]
+#![allow(non_upper_case_globals)]
+
+use prelude::v1::*;
+use io::prelude::*;
+
+use ffi::AsOsStr;
+use fmt;
+use io::{self, Error, ErrorKind};
+use path::AsPath;
+use libc;
+use sync::mpsc::{channel, Receiver};
+use sys::pipe2::{self, AnonPipe};
+use sys::process2::Process as ProcessImp;
+use sys::process2::Command as CommandImp;
+use sys::process2::ExitStatus as ExitStatusImp;
+use sys_common::{AsInner, AsInnerMut};
+use thread::Thread;
+
+/// Representation of a running or exited child process.
+///
+/// This structure is used to represent and manage child processes. A child
+/// process is created via the `Command` struct, which configures the spawning
+/// process and can itself be constructed using a builder-style interface.
+///
+/// # Example
+///
+/// ```should_fail
+/// # #![feature(process)]
+///
+/// use std::process::Command;
+///
+/// let output = Command::new("/bin/cat").arg("file.txt").output().unwrap_or_else(|e| {
+///     panic!("failed to execute child: {}", e)
+/// });
+/// let contents = output.stdout;
+/// assert!(output.status.success());
+/// ```
+pub struct Child {
+    handle: ProcessImp,
+
+    /// None until wait() or wait_with_output() is called.
+    status: Option<ExitStatusImp>,
+
+    /// The handle for writing to the child's stdin, if it has been captured
+    pub stdin: Option<ChildStdin>,
+
+    /// The handle for reading from the child's stdout, if it has been captured
+    pub stdout: Option<ChildStdout>,
+
+    /// The handle for reading from the child's stderr, if it has been captured
+    pub stderr: Option<ChildStderr>,
+}
+
+/// A handle to a child procesess's stdin
+pub struct ChildStdin {
+    inner: AnonPipe
+}
+
+impl Write for ChildStdin {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.inner.write(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+/// A handle to a child procesess's stdout
+pub struct ChildStdout {
+    inner: AnonPipe
+}
+
+impl Read for ChildStdout {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+}
+
+/// A handle to a child procesess's stderr
+pub struct ChildStderr {
+    inner: AnonPipe
+}
+
+impl Read for ChildStderr {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+}
+
+/// The `Command` type acts as a process builder, providing fine-grained control
+/// over how a new process should be spawned. A default configuration can be
+/// generated using `Command::new(program)`, where `program` gives a path to the
+/// program to be executed. Additional builder methods allow the configuration
+/// to be changed (for example, by adding arguments) prior to spawning:
+///
+/// ```
+/// # #![feature(process)]
+///
+/// use std::process::Command;
+///
+/// let output = Command::new("sh").arg("-c").arg("echo hello").output().unwrap_or_else(|e| {
+///   panic!("failed to execute process: {}", e)
+/// });
+/// let hello = output.stdout;
+/// ```
+pub struct Command {
+    inner: CommandImp,
+
+    // Details explained in the builder methods
+    stdin: Option<StdioImp>,
+    stdout: Option<StdioImp>,
+    stderr: Option<StdioImp>,
+}
+
+impl Command {
+    /// Constructs a new `Command` for launching the program at
+    /// path `program`, with the following default configuration:
+    ///
+    /// * No arguments to the program
+    /// * Inherit the current process's environment
+    /// * Inherit the current process's working directory
+    /// * Inherit stdin/stdout/stderr for `run` or `status`, but create pipes for `output`
+    ///
+    /// Builder methods are provided to change these defaults and
+    /// otherwise configure the process.
+    pub fn new<S: AsOsStr + ?Sized>(program: &S) -> Command {
+        Command {
+            inner: CommandImp::new(program.as_os_str()),
+            stdin: None,
+            stdout: None,
+            stderr: None,
+        }
+    }
+
+    /// Add an argument to pass to the program.
+    pub fn arg<S: AsOsStr + ?Sized>(&mut self, arg: &S) -> &mut Command {
+        self.inner.arg(arg.as_os_str());
+        self
+    }
+
+    /// Add multiple arguments to pass to the program.
+    pub fn args<S: AsOsStr>(&mut self, args: &[S]) -> &mut Command {
+        self.inner.args(args.iter().map(AsOsStr::as_os_str));
+        self
+    }
+
+    /// Inserts or updates an environment variable mapping.
+    ///
+    /// Note that environment variable names are case-insensitive (but case-preserving) on Windows,
+    /// and case-sensitive on all other platforms.
+    pub fn env<S: ?Sized, T: ?Sized>(&mut self, key: &S, val: &T) -> &mut Command where
+        S: AsOsStr, T: AsOsStr
+    {
+        self.inner.env(key.as_os_str(), val.as_os_str());
+        self
+    }
+
+    /// Removes an environment variable mapping.
+    pub fn env_remove<S: ?Sized + AsOsStr>(&mut self, key: &S) -> &mut Command {
+        self.inner.env_remove(key.as_os_str());
+        self
+    }
+
+    /// Clears the entire environment map for the child process.
+    pub fn env_clear(&mut self) -> &mut Command {
+        self.inner.env_clear();
+        self
+    }
+
+    /// Set the working directory for the child process.
+    pub fn current_dir<P: AsPath + ?Sized>(&mut self, dir: &P) -> &mut Command {
+        self.inner.cwd(dir.as_path().as_os_str());
+        self
+    }
+
+    /// Configuration for the child process's stdin handle (file descriptor 0).
+    /// Defaults to `CreatePipe(true, false)` so the input can be written to.
+    pub fn stdin(&mut self, cfg: Stdio) -> &mut Command {
+        self.stdin = Some(cfg.0);
+        self
+    }
+
+    /// Configuration for the child process's stdout handle (file descriptor 1).
+    /// Defaults to `CreatePipe(false, true)` so the output can be collected.
+    pub fn stdout(&mut self, cfg: Stdio) -> &mut Command {
+        self.stdout = Some(cfg.0);
+        self
+    }
+
+    /// Configuration for the child process's stderr handle (file descriptor 2).
+    /// Defaults to `CreatePipe(false, true)` so the output can be collected.
+    pub fn stderr(&mut self, cfg: Stdio) -> &mut Command {
+        self.stderr = Some(cfg.0);
+        self
+    }
+
+    fn spawn_inner(&self, default_io: StdioImp) -> io::Result<Child> {
+        let (their_stdin, our_stdin) = try!(
+            setup_io(self.stdin.as_ref().unwrap_or(&default_io), 0, true)
+        );
+        let (their_stdout, our_stdout) = try!(
+            setup_io(self.stdout.as_ref().unwrap_or(&default_io), 1, false)
+        );
+        let (their_stderr, our_stderr) = try!(
+            setup_io(self.stderr.as_ref().unwrap_or(&default_io), 2, false)
+        );
+
+        match ProcessImp::spawn(&self.inner, their_stdin, their_stdout, their_stderr) {
+            Err(e) => Err(e),
+            Ok(handle) => Ok(Child {
+                handle: handle,
+                status: None,
+                stdin: our_stdin.map(|fd| ChildStdin { inner: fd }),
+                stdout: our_stdout.map(|fd| ChildStdout { inner: fd }),
+                stderr: our_stderr.map(|fd| ChildStderr { inner: fd }),
+            })
+        }
+    }
+
+    /// Executes the command as a child process, returning a handle to it.
+    ///
+    /// By default, stdin, stdout and stderr are inherited by the parent.
+    pub fn spawn(&mut self) -> io::Result<Child> {
+        self.spawn_inner(StdioImp::Inherit)
+    }
+
+    /// Executes the command as a child process, waiting for it to finish and
+    /// collecting all of its output.
+    ///
+    /// By default, stdin, stdout and stderr are captured (and used to
+    /// provide the resulting output).
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # #![feature(process)]
+    /// use std::process::Command;
+    ///
+    /// let output = Command::new("cat").arg("foot.txt").output().unwrap_or_else(|e| {
+    ///     panic!("failed to execute process: {}", e)
+    /// });
+    ///
+    /// println!("status: {}", output.status);
+    /// println!("stdout: {}", String::from_utf8_lossy(output.stdout.as_slice()));
+    /// println!("stderr: {}", String::from_utf8_lossy(output.stderr.as_slice()));
+    /// ```
+    pub fn output(&mut self) -> io::Result<Output> {
+        self.spawn_inner(StdioImp::Capture).and_then(|p| p.wait_with_output())
+    }
+
+    /// 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 by the parent.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # #![feature(process)]
+    /// use std::process::Command;
+    ///
+    /// let status = Command::new("ls").status().unwrap_or_else(|e| {
+    ///     panic!("failed to execute process: {}", e)
+    /// });
+    ///
+    /// println!("process exited with: {}", status);
+    /// ```
+    pub fn status(&mut self) -> io::Result<ExitStatus> {
+        self.spawn().and_then(|mut p| p.wait())
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Debug for Command {
+    /// Format the program and arguments of a Command for display. Any
+    /// non-utf8 data is lossily converted using the utf8 replacement
+    /// character.
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "{:?}", self.inner.program));
+        for arg in &self.inner.args {
+            try!(write!(f, " {:?}", arg));
+        }
+        Ok(())
+    }
+}
+
+impl AsInner<CommandImp> for Command {
+    fn as_inner(&self) -> &CommandImp { &self.inner }
+}
+
+impl AsInnerMut<CommandImp> for Command {
+    fn as_inner_mut(&mut self) -> &mut CommandImp { &mut self.inner }
+}
+
+fn setup_io(io: &StdioImp, fd: libc::c_int, readable: bool)
+            -> io::Result<(Option<AnonPipe>, Option<AnonPipe>)>
+{
+    use self::StdioImp::*;
+    Ok(match *io {
+        Null => {
+            (None, None)
+        }
+        Inherit => {
+            (Some(AnonPipe::from_fd(fd)), None)
+        }
+        Capture => {
+            let (reader, writer) = try!(unsafe { pipe2::anon_pipe() });
+            if readable {
+                (Some(reader), Some(writer))
+            } else {
+                (Some(writer), Some(reader))
+            }
+        }
+    })
+}
+
+/// The output of a finished process.
+#[derive(PartialEq, Eq, Clone)]
+pub struct Output {
+    /// The status (exit code) of the process.
+    pub status: ExitStatus,
+    /// The data that the process wrote to stdout.
+    pub stdout: Vec<u8>,
+    /// The data that the process wrote to stderr.
+    pub stderr: Vec<u8>,
+}
+
+/// Describes what to do with a standard io stream for a child process.
+pub struct Stdio(StdioImp);
+
+// The internal enum for stdio setup; see below for descriptions.
+#[derive(Clone)]
+enum StdioImp {
+    Capture,
+    Inherit,
+    Null,
+}
+
+impl Stdio {
+    /// A new pipe should be arranged to connect the parent and child processes.
+    pub fn capture() -> Stdio { Stdio(StdioImp::Capture) }
+
+    /// The child inherits from the corresponding parent descriptor.
+    pub fn inherit() -> Stdio { Stdio(StdioImp::Capture) }
+
+    /// This stream will be ignored. This is the equivalent of attaching the
+    /// stream to `/dev/null`
+    pub fn null() -> Stdio { Stdio(StdioImp::Capture) }
+}
+
+/// Describes the result of a process after it has terminated.
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct ExitStatus(ExitStatusImp);
+
+impl ExitStatus {
+    /// Was termination successful? Signal termination not considered a success,
+    /// and success is defined as a zero exit status.
+    pub fn success(&self) -> bool {
+        self.0.success()
+    }
+
+    /// Return the exit code of the process, if any.
+    ///
+    /// On Unix, this will return `None` if the process was terminated
+    /// by a signal; `std::os::unix` provides an extension trait for
+    /// extracting the signal and other details from the `ExitStatus`.
+    pub fn code(&self) -> Option<i32> {
+        self.0.code()
+    }
+}
+
+impl AsInner<ExitStatusImp> for ExitStatus {
+    fn as_inner(&self) -> &ExitStatusImp { &self.0 }
+}
+
+impl fmt::Display for ExitStatus {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl Child {
+    /// Forces the child to exit. This is equivalent to sending a
+    /// SIGKILL on unix platforms.
+    pub fn kill(&mut self) -> io::Result<()> {
+        #[cfg(unix)] fn collect_status(p: &mut Child) {
+            // On Linux (and possibly other unices), a process that has exited will
+            // continue to accept signals because it is "defunct". The delivery of
+            // signals will only fail once the child has been reaped. For this
+            // reason, if the process hasn't exited yet, then we attempt to collect
+            // their status with WNOHANG.
+            if p.status.is_none() {
+                match p.handle.try_wait() {
+                    Some(status) => { p.status = Some(status); }
+                    None => {}
+                }
+            }
+        }
+        #[cfg(windows)] fn collect_status(_p: &mut Child) {}
+
+        collect_status(self);
+
+        // if the process has finished, and therefore had waitpid called,
+        // and we kill it, then on unix we might ending up killing a
+        // newer process that happens to have the same (re-used) id
+        if self.status.is_some() {
+            return Err(Error::new(
+                ErrorKind::InvalidInput,
+                "invalid argument: can't kill an exited process",
+                None
+            ))
+        }
+
+        unsafe { self.handle.kill() }
+    }
+
+    /// Wait for the child to exit completely, returning the status that it
+    /// exited with. This function will continue to have the same return value
+    /// after it has been called at least once.
+    ///
+    /// 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.
+    pub fn wait(&mut self) -> io::Result<ExitStatus> {
+        drop(self.stdin.take());
+        match self.status {
+            Some(code) => Ok(ExitStatus(code)),
+            None => {
+                let status = try!(self.handle.wait());
+                self.status = Some(status);
+                Ok(ExitStatus(status))
+            }
+        }
+    }
+
+    /// Simultaneously wait for the child to exit and collect all remaining
+    /// output on the stdout/stderr handles, returning a `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.
+    pub fn wait_with_output(mut self) -> io::Result<Output> {
+        drop(self.stdin.take());
+        fn read<T: Read + Send>(stream: Option<T>) -> Receiver<io::Result<Vec<u8>>> {
+            let (tx, rx) = channel();
+            match stream {
+                Some(stream) => {
+                    Thread::spawn(move || {
+                        let mut stream = stream;
+                        let mut ret = Vec::new();
+                        let res = stream.read_to_end(&mut ret);
+                        tx.send(res.map(|_| ret)).unwrap();
+                    });
+                }
+                None => tx.send(Ok(Vec::new())).unwrap()
+            }
+            rx
+        }
+        let stdout = read(self.stdout.take());
+        let stderr = read(self.stderr.take());
+        let status = try!(self.wait());
+
+        Ok(Output {
+            status: status,
+            stdout: stdout.recv().unwrap().unwrap_or(Vec::new()),
+            stderr:  stderr.recv().unwrap().unwrap_or(Vec::new()),
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use io::ErrorKind;
+    use io::prelude::*;
+    use prelude::v1::{Ok, Err, range, drop, Some, None, Vec};
+    use prelude::v1::{String, Clone};
+    use prelude::v1::{SliceExt, Str, StrExt, AsSlice, ToString, GenericPath};
+    use path::Path;
+    use old_path;
+    use old_io::fs::PathExtensions;
+    use rt::running_on_valgrind;
+    use str;
+    use super::{Child, Command, Output, ExitStatus, Stdio};
+    use sync::mpsc::channel;
+    use thread::Thread;
+    use time::Duration;
+
+    // FIXME(#10380) these tests should not all be ignored on android.
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn smoke() {
+        let p = Command::new("true").spawn();
+        assert!(p.is_ok());
+        let mut p = p.unwrap();
+        assert!(p.wait().unwrap().success());
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn smoke_failure() {
+        match Command::new("if-this-is-a-binary-then-the-world-has-ended").spawn() {
+            Ok(..) => panic!(),
+            Err(..) => {}
+        }
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn exit_reported_right() {
+        let p = Command::new("false").spawn();
+        assert!(p.is_ok());
+        let mut p = p.unwrap();
+        assert!(p.wait().unwrap().code() == Some(1));
+        drop(p.wait().clone());
+    }
+
+    #[cfg(all(unix, not(target_os="android")))]
+    #[test]
+    fn signal_reported_right() {
+        use os::unix::ExitStatusExt;
+
+        let p = Command::new("/bin/sh").arg("-c").arg("kill -1 $$").spawn();
+        assert!(p.is_ok());
+        let mut p = p.unwrap();
+        match p.wait().unwrap().signal() {
+            Some(1) => {},
+            result => panic!("not terminated by signal 1 (instead, {:?})", result),
+        }
+    }
+
+    pub fn run_output(mut cmd: Command) -> String {
+        let p = cmd.spawn();
+        assert!(p.is_ok());
+        let mut p = p.unwrap();
+        assert!(p.stdout.is_some());
+        let mut ret = String::new();
+        p.stdout.as_mut().unwrap().read_to_string(&mut ret).unwrap();
+        assert!(p.wait().unwrap().success());
+        return ret;
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn stdout_works() {
+        let mut cmd = Command::new("echo");
+        cmd.arg("foobar").stdout(Stdio::capture());
+        assert_eq!(run_output(cmd), "foobar\n");
+    }
+
+    #[cfg(all(unix, not(target_os="android")))]
+    #[test]
+    fn set_current_dir_works() {
+        let mut cmd = Command::new("/bin/sh");
+        cmd.arg("-c").arg("pwd")
+           .current_dir("/")
+           .stdout(Stdio::capture());
+        assert_eq!(run_output(cmd), "/\n");
+    }
+
+    #[cfg(all(unix, not(target_os="android")))]
+    #[test]
+    fn stdin_works() {
+        let mut p = Command::new("/bin/sh")
+                            .arg("-c").arg("read line; echo $line")
+                            .stdin(Stdio::capture())
+                            .stdout(Stdio::capture())
+                            .spawn().unwrap();
+        p.stdin.as_mut().unwrap().write("foobar".as_bytes()).unwrap();
+        drop(p.stdin.take());
+        let mut out = String::new();
+        p.stdout.as_mut().unwrap().read_to_string(&mut out).unwrap();
+        assert!(p.wait().unwrap().success());
+        assert_eq!(out, "foobar\n");
+    }
+
+
+    #[cfg(all(unix, not(target_os="android")))]
+    #[test]
+    fn uid_works() {
+        use os::unix::*;
+        use libc;
+        let mut p = Command::new("/bin/sh")
+                            .arg("-c").arg("true")
+                            .uid(unsafe { libc::getuid() })
+                            .gid(unsafe { libc::getgid() })
+                            .spawn().unwrap();
+        assert!(p.wait().unwrap().success());
+    }
+
+    #[cfg(all(unix, not(target_os="android")))]
+    #[test]
+    fn uid_to_root_fails() {
+        use os::unix::*;
+        use libc;
+
+        // if we're already root, this isn't a valid test. Most of the bots run
+        // as non-root though (android is an exception).
+        if unsafe { libc::getuid() == 0 } { return }
+        assert!(Command::new("/bin/ls").uid(0).gid(0).spawn().is_err());
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_process_status() {
+        let mut status = Command::new("false").status().unwrap();
+        assert!(status.code() == Some(1));
+
+        status = Command::new("true").status().unwrap();
+        assert!(status.success());
+    }
+
+    #[test]
+    fn test_process_output_fail_to_start() {
+        match Command::new("/no-binary-by-this-name-should-exist").output() {
+            Err(e) => assert_eq!(e.kind(), ErrorKind::FileNotFound),
+            Ok(..) => panic!()
+        }
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_process_output_output() {
+        let Output {status, stdout, stderr}
+             = Command::new("echo").arg("hello").output().unwrap();
+        let output_str = str::from_utf8(stdout.as_slice()).unwrap();
+
+        assert!(status.success());
+        assert_eq!(output_str.trim().to_string(), "hello");
+        // FIXME #7224
+        if !running_on_valgrind() {
+            assert_eq!(stderr, Vec::new());
+        }
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_process_output_error() {
+        let Output {status, stdout, stderr}
+             = Command::new("mkdir").arg(".").output().unwrap();
+
+        assert!(status.code() == Some(1));
+        assert_eq!(stdout, Vec::new());
+        assert!(!stderr.is_empty());
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_finish_once() {
+        let mut prog = Command::new("false").spawn().unwrap();
+        assert!(prog.wait().unwrap().code() == Some(1));
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_finish_twice() {
+        let mut prog = Command::new("false").spawn().unwrap();
+        assert!(prog.wait().unwrap().code() == Some(1));
+        assert!(prog.wait().unwrap().code() == Some(1));
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_wait_with_output_once() {
+        let prog = Command::new("echo").arg("hello").stdout(Stdio::capture())
+            .spawn().unwrap();
+        let Output {status, stdout, stderr} = prog.wait_with_output().unwrap();
+        let output_str = str::from_utf8(stdout.as_slice()).unwrap();
+
+        assert!(status.success());
+        assert_eq!(output_str.trim().to_string(), "hello");
+        // FIXME #7224
+        if !running_on_valgrind() {
+            assert_eq!(stderr, Vec::new());
+        }
+    }
+
+    #[cfg(all(unix, not(target_os="android")))]
+    pub fn pwd_cmd() -> Command {
+        Command::new("pwd")
+    }
+    #[cfg(target_os="android")]
+    pub fn pwd_cmd() -> Command {
+        let mut cmd = Command::new("/system/bin/sh");
+        cmd.arg("-c").arg("pwd");
+        cmd
+    }
+
+    #[cfg(windows)]
+    pub fn pwd_cmd() -> Command {
+        let mut cmd = Command::new("cmd");
+        cmd.arg("/c").arg("cd");
+        cmd
+    }
+
+    #[test]
+    fn test_keep_current_working_dir() {
+        use os;
+        let prog = pwd_cmd().spawn().unwrap();
+
+        let output = String::from_utf8(prog.wait_with_output().unwrap().stdout).unwrap();
+        let parent_dir = os::getcwd().unwrap();
+        let child_dir = old_path::Path::new(output.trim());
+
+        let parent_stat = parent_dir.stat().unwrap();
+        let child_stat = child_dir.stat().unwrap();
+
+        assert_eq!(parent_stat.unstable.device, child_stat.unstable.device);
+        assert_eq!(parent_stat.unstable.inode, child_stat.unstable.inode);
+    }
+
+    #[test]
+    fn test_change_working_directory() {
+        use os;
+        // test changing to the parent of os::getcwd() because we know
+        // the path exists (and os::getcwd() is not expected to be root)
+        let parent_dir = os::getcwd().unwrap().dir_path();
+        let result = pwd_cmd().current_dir(&parent_dir).output().unwrap();
+
+        let output = String::from_utf8(result.stdout).unwrap();
+        let child_dir = old_path::Path::new(output.trim());
+
+        let parent_stat = parent_dir.stat().unwrap();
+        let child_stat = child_dir.stat().unwrap();
+
+        assert_eq!(parent_stat.unstable.device, child_stat.unstable.device);
+        assert_eq!(parent_stat.unstable.inode, child_stat.unstable.inode);
+    }
+
+    #[cfg(all(unix, not(target_os="android")))]
+    pub fn env_cmd() -> Command {
+        Command::new("env")
+    }
+    #[cfg(target_os="android")]
+    pub fn env_cmd() -> Command {
+        let mut cmd = Command::new("/system/bin/sh");
+        cmd.arg("-c").arg("set");
+        cmd
+    }
+
+    #[cfg(windows)]
+    pub fn env_cmd() -> Command {
+        let mut cmd = Command::new("cmd");
+        cmd.arg("/c").arg("set");
+        cmd
+    }
+
+    #[cfg(not(target_os="android"))]
+    #[test]
+    fn test_inherit_env() {
+        use os;
+        if running_on_valgrind() { return; }
+
+        let result = env_cmd().output().unwrap();
+        let output = String::from_utf8(result.stdout).unwrap();
+
+        let r = os::env();
+        for &(ref k, ref v) in &r {
+            // don't check windows magical empty-named variables
+            assert!(k.is_empty() ||
+                    output.contains(format!("{}={}", *k, *v).as_slice()),
+                    "output doesn't contain `{}={}`\n{}",
+                    k, v, output);
+        }
+    }
+    #[cfg(target_os="android")]
+    #[test]
+    fn test_inherit_env() {
+        use os;
+        if running_on_valgrind() { return; }
+
+        let mut result = env_cmd().output().unwrap();
+        let output = String::from_utf8(result.stdout).unwrap();
+
+        let r = os::env();
+        for &(ref k, ref v) in &r {
+            // don't check android RANDOM variables
+            if *k != "RANDOM".to_string() {
+                assert!(output.contains(format!("{}={}",
+                                                *k,
+                                                *v).as_slice()) ||
+                        output.contains(format!("{}=\'{}\'",
+                                                *k,
+                                                *v).as_slice()));
+            }
+        }
+    }
+
+    #[test]
+    fn test_override_env() {
+        use env;
+
+        // In some build environments (such as chrooted Nix builds), `env` can
+        // only be found in the explicitly-provided PATH env variable, not in
+        // default places such as /bin or /usr/bin. So we need to pass through
+        // PATH to our sub-process.
+        let mut cmd = env_cmd();
+        cmd.env_clear().env("RUN_TEST_NEW_ENV", "123");
+        if let Some(p) = env::var_os("PATH") {
+            cmd.env("PATH", &p);
+        }
+        let result = cmd.output().unwrap();
+        let output = String::from_utf8_lossy(result.stdout.as_slice()).to_string();
+
+        assert!(output.contains("RUN_TEST_NEW_ENV=123"),
+                "didn't find RUN_TEST_NEW_ENV inside of:\n\n{}", output);
+    }
+
+    #[test]
+    fn test_add_to_env() {
+        let result = env_cmd().env("RUN_TEST_NEW_ENV", "123").output().unwrap();
+        let output = String::from_utf8_lossy(result.stdout.as_slice()).to_string();
+
+        assert!(output.contains("RUN_TEST_NEW_ENV=123"),
+                "didn't find RUN_TEST_NEW_ENV inside of:\n\n{}", output);
+    }
+}