asyncio.docs: Document subprocess_exec and subprocess_shell. Issue #20694.

Doc/library/asyncio-eventloop.rst

@@ -467,17 +467,61 @@ Run subprocesses asynchronously using the :mod:`subprocess` module.
    :class:`SelectSelector` or :class:`PollSelector` to handle character devices
    on Mac OS X 10.6 (Snow Leopard) and later.
 
-.. method:: BaseEventLoop.subprocess_exec(protocol_factory, \*args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=False, shell=False, bufsize=0, \*\*kwargs)
+.. method:: BaseEventLoop.subprocess_exec(protocol_factory, \*args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, \*\*kwargs)
 
-   XXX
+   Create a subprocess from one or more string arguments, where the first string
+   specifies the program to execute, and the remaining strings specify the
+   program's arguments. (Thus, together the string arguments form the
+   ``sys.argv`` value of the program, assuming it is a Python script.) This is
+   similar to the standard library :class:`subprocess.Popen` class called with
+   shell=False and the list of strings passed as the first argument;
+   however, where :class:`~subprocess.Popen` takes a single argument which is
+   list of strings, :func:`subprocess_exec` takes multiple string arguments.
+
+   Other parameters:
+
+   * *stdin*: Either a file-like object representing the pipe to be connected
+     to the subprocess's standard input stream using
+     :meth:`~BaseEventLoop.connect_write_pipe`, or the constant
+     :const:`subprocess.PIPE` (the default). By default a new pipe will be
+     created and connected.
+
+   * *stdout*: Either a file-like object representing the pipe to be connected
+     to the subprocess's standard output stream using
+     :meth:`~BaseEventLoop.connect_write_pipe`, or the constant
+     :const:`subprocess.PIPE` (the default). By default a new pipe will be
+     created and connected.
+
+   * *stderr*: Either a file-like object representing the pipe to be connected
+     to the subprocess's standard error stream using
+     :meth:`~BaseEventLoop.connect_read_pipe`, or one of the constants
+     :const:`subprocess.PIPE` (the default) or :const:`subprocess.STDOUT`.
+     By default a new pipe will be created and connected. When
+     :const:`subprocess.STDOUT` is specified, the subprocess's standard error
+     stream will be connected to the same pipe as the standard output stream.
+
+   * All other keyword arguments are passed to :class:`subprocess.Popen`
+     without interpretation, except for *bufsize*, *universal_newlines* and
+     *shell*, which should not be specified at all.
+
+   Returns a pair of ``(transport, protocol)``, where *transport* is an
+   instance of :class:`BaseSubprocessTransport`.
 
    This method is a :ref:`coroutine <coroutine>`.
 
    See the constructor of the :class:`subprocess.Popen` class for parameters.
 
-.. method:: BaseEventLoop.subprocess_shell(protocol_factory, cmd, \*, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=False, shell=True, bufsize=0, \*\*kwargs)
+.. method:: BaseEventLoop.subprocess_shell(protocol_factory, cmd, \*, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, \*\*kwargs)
 
-   XXX
+   Create a subprocess from *cmd*, which is a string using the platform's
+   "shell" syntax. This is similar to the standard library
+   :class:`subprocess.Popen` class called with ``shell=True``.
+
+   See :meth:`~BaseEventLoop.subprocess_exec` for more details about
+   the remaining arguments.
+
+   Returns a pair of ``(transport, protocol)``, where *transport* is an
+   instance of :class:`BaseSubprocessTransport`.
 
    This method is a :ref:`coroutine <coroutine>`.