Function launch

src/common/command_utils.cpp:44–105

namespace command {

static Future<string> launch(
    const string& path,
    const vector<string>& argv)
{
  Try<Subprocess> s = subprocess(
      path,
      argv,
      Subprocess::PATH(os::DEV_NULL),
      Subprocess::PIPE(),
      Subprocess::PIPE());

  string command = strings::join(
      ", ",
      path,
      strings::join(", ", argv));

  if (s.isError()) {
    return Failure(
        "Failed to execute the subprocess '" + command + "': " + s.error());
  }

  return await(
      s->status(),
      process::io::read(s->out().get()),
      process::io::read(s->err().get()))
    .then([command](const tuple<
        Future<Option<int>>,
        Future<string>,
        Future<string>>& t) -> Future<string> {
      const Future<Option<int>>& status = std::get<0>(t);
      if (!status.isReady()) {
        return Failure(
            "Failed to get the exit status of the subprocess: " +
            (status.isFailed() ? status.failure() : "discarded"));
      }

      if (status->isNone()) {
        return Failure("Failed to reap the subprocess");
      }

      if (status->get() != 0) {
        const Future<string>& error = std::get<2>(t);
        if (!error.isReady()) {
            return Failure(
                "Unexpected result from the subprocess: " +
                 WSTRINGIFY(status->get()) + ", stderr='" +
                 error.get() + "'");
        }

        return Failure("Subprocess '" + command + "' failed: " + error.get());
      }

      const Future<string>& output = std::get<1>(t);
      if (!output.isReady()) {
         return Failure(
            "Failed to read stdout from '" + command + "': " +
            (output.isFailed() ? output.failure() : "discarded"));
      }