Function subprocess

3rdparty/libprocess/src/subprocess.cpp:316–467

Executes a subprocess. NOTE: On Windows, components of the `path` and `argv` that need to be quoted are expected to have been quoted before they are passed to `subprocess. For example, either of these may contain paths with spaces in them, like `C:\"Program Files"\foo.exe`, where notably the character sequence `\"` is not escaped quote, but instead a path separator and the start of a path compone

// escape it. Therefore, incorrectly-quoted command arguments will probably
// lead the child process to terminate with an error.
Try<Subprocess> subprocess(
    const string& path,
    vector<string> argv,
    const Subprocess::IO& in,
    const Subprocess::IO& out,
    const Subprocess::IO& err,
    const flags::FlagsBase* flags,
    const Option<map<string, string>>& environment,
    const Option<lambda::function<
        pid_t(const lambda::function<int()>&)>>& _clone,
    const vector<Subprocess::ParentHook>& parent_hooks,
    const vector<Subprocess::ChildHook>& child_hooks,
    const vector<int_fd>& whitelist_fds)
{
  // TODO(hausdorff): We should error out on Windows here if we are passing
  // parameters that aren't used.

  // File descriptors for redirecting stdin/stdout/stderr.
  // These file descriptors are used for different purposes depending
  // on the specified I/O modes.
  // See `Subprocess::PIPE`, `Subprocess::PATH`, and `Subprocess::FD`.
  InputFileDescriptors stdinfds;
  OutputFileDescriptors stdoutfds;
  OutputFileDescriptors stderrfds;

  // Prepare the file descriptor(s) for stdin.
  Try<InputFileDescriptors> input = in.input();
  if (input.isError()) {
    return Error(input.error());
  }

  stdinfds = input.get();

  // Prepare the file descriptor(s) for stdout.
  Try<OutputFileDescriptors> output = out.output();
  if (output.isError()) {
    process::internal::close(stdinfds, stdoutfds, stderrfds);
    return Error(output.error());
  }

  stdoutfds = output.get();

  // Prepare the file descriptor(s) for stderr.
  output = err.output();
  if (output.isError()) {
    process::internal::close(stdinfds, stdoutfds, stderrfds);
    return Error(output.error());
  }

  stderrfds = output.get();

#ifndef __WINDOWS__
  // TODO(jieyu): Consider using O_CLOEXEC for atomic close-on-exec.
  Try<Nothing> cloexec = internal::cloexec(stdinfds, stdoutfds, stderrfds);
  if (cloexec.isError()) {
    process::internal::close(stdinfds, stdoutfds, stderrfds);
    return Error("Failed to cloexec: " + cloexec.error());
  }