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.. currentmodule:: asyncio Subprocess ========== Create a subprocess ------------------- .. function:: create_subprocess_shell(cmd, stdin=None, stdout=None, stderr=None, loop=None, limit=None, \*\*kwds) Run the shell command *cmd* given as a string. Return a :class:`~asyncio.subprocess.Process` instance. This function is a :ref:`coroutine <coroutine>`. .. function:: create_subprocess_exec(\*args, stdin=None, stdout=None, stderr=None, loop=None, limit=None, \*\*kwds) Create a subprocess. Return a :class:`~asyncio.subprocess.Process` instance. This function is a :ref:`coroutine <coroutine>`. Use the :meth:`BaseEventLoop.connect_read_pipe` and :meth:`BaseEventLoop.connect_write_pipe` methods to connect pipes. .. seealso:: The :meth:`BaseEventLoop.subprocess_exec` and :meth:`BaseEventLoop.subprocess_shell` methods. Constants --------- .. data:: asyncio.subprocess.PIPE Special value that can be used as the *stdin*, *stdout* or *stderr* argument to :func:`create_subprocess_shell` and :func:`create_subprocess_exec` and indicates that a pipe to the standard stream should be opened. .. data:: asyncio.subprocess.STDOUT Special value that can be used as the *stderr* argument to :func:`create_subprocess_shell` and :func:`create_subprocess_exec` and indicates that standard error should go into the same handle as standard output. .. data:: asyncio.subprocess.DEVNULL Special value that can be used as the *stderr* argument to :func:`create_subprocess_shell` and :func:`create_subprocess_exec` and indicates that standard error should go into the same handle as standard output. Process ------- .. class:: asyncio.subprocess.Process .. attribute:: pid The identifier of the process. Note that if you set the *shell* argument to ``True``, this is the process identifier of the spawned shell. .. attribute:: returncode Return code of the process when it exited. A ``None`` value indicates that the process has not terminated yet. A negative value ``-N`` indicates that the child was terminated by signal ``N`` (Unix only). .. attribute:: stdin Standard input stream (write), ``None`` if the process was created with ``stdin=None``. .. attribute:: stdout Standard output stream (read), ``None`` if the process was created with ``stdout=None``. .. attribute:: stderr Standard error stream (read), ``None`` if the process was created with ``stderr=None``. .. method:: communicate(input=None) Interact with process: Send data to stdin. Read data from stdout and stderr, until end-of-file is reached. Wait for process to terminate. The optional *input* argument should be data to be sent to the child process, or ``None``, if no data should be sent to the child. The type of *input* must be bytes. :meth:`communicate` returns a tuple ``(stdoutdata, stderrdata)``. Note that if you want to send data to the process's stdin, you need to create the Process object with ``stdin=PIPE``. Similarly, to get anything other than ``None`` in the result tuple, you need to give ``stdout=PIPE`` and/or ``stderr=PIPE`` too. .. note:: The data read is buffered in memory, so do not use this method if the data size is large or unlimited. This method is a :ref:`coroutine <coroutine>`. .. method:: kill() Kills the child. On Posix OSs the function sends :py:data:`SIGKILL` to the child. On Windows :meth:`kill` is an alias for :meth:`terminate`. .. method:: send_signal(signal) Sends the signal *signal* to the child process. .. note:: On Windows, :py:data:`SIGTERM` is an alias for :meth:`terminate`. ``CTRL_C_EVENT`` and ``CTRL_BREAK_EVENT`` can be sent to processes started with a *creationflags* parameter which includes ``CREATE_NEW_PROCESS_GROUP``. .. method:: terminate() Stop the child. On Posix OSs the method sends :py:data:`signal.SIGTERM` to the child. On Windows the Win32 API function :c:func:`TerminateProcess` is called to stop the child. .. method:: wait(): Wait for child process to terminate. Set and return :attr:`returncode` attribute. This method is a :ref:`coroutine <coroutine>`. Example ------- Implement a function similar to :func:`subprocess.getstatusoutput`, except that it does not use a shell. Get the output of the "python -m platform" command and display the output:: import asyncio import sys from asyncio import subprocess @asyncio.coroutine def getstatusoutput(*args): proc = yield from asyncio.create_subprocess_exec( *args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) try: stdout, _ = yield from proc.communicate() except: proc.kill() yield from proc.wait() raise exitcode = yield from proc.wait() return (exitcode, stdout) loop = asyncio.get_event_loop() coro = getstatusoutput(sys.executable, '-m', 'platform') exitcode, stdout = loop.run_until_complete(coro) if not exitcode: stdout = stdout.decode('ascii').rstrip() print("Platform: %s" % stdout) else: print("Python failed with exit code %s:" % exitcode) sys.stdout.flush() sys.stdout.buffer.flush() sys.stdout.buffer.write(stdout) sys.stdout.buffer.flush() loop.close()


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