daemon.py 文件源码

def redirect_stream(system_stream, target_stream):
    """ Redirect a system stream to a specified file.

        :param standard_stream: A file object representing a standard I/O
            stream.
        :param target_stream: The target file object for the redirected
            stream, or ``None`` to specify the null device.
        :return: ``None``.

        `system_stream` is a standard system stream such as
        ``sys.stdout``. `target_stream` is an open file object that
        should replace the corresponding system stream object.

        If `target_stream` is ``None``, defaults to opening the
        operating system's null device and using its file descriptor.

        """
    if target_stream is None:
        target_fd = os.open(os.devnull, os.O_RDWR)
    else:
        target_fd = target_stream.fileno()
    os.dup2(target_fd, system_stream.fileno())