From: Gregory P. Smith <greg@krypto.org>
Date: Tue, 15 Apr 2014 14:59:44 +0000 (-0700)
Subject: Some cleanup of the subprocess docs in 2.7.  Adds a reference to the
X-Git-Tag: v2.7.7rc1~58
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=8f813fe2f2932fb03ce8b1b5eb96168f1f3a5bc4;p=python

Some cleanup of the subprocess docs in 2.7.  Adds a reference to the
subprocess32 project in PyPI for posix users.
---

diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 9eba597341..54149ebf54 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -20,20 +20,26 @@ replace several older modules and functions::
    popen2.*
    commands.*
 
-Information about how the :mod:`subprocess` module can be used to replace these
-modules and functions can be found in the following sections.
+Information about how this module can be used to replace the older
+functions can be found in the subprocess-replacements_ section.
 
 .. seealso::
 
+   POSIX users (Linux, BSD, etc.) are strongly encouraged to install
+   and use the much more recent subprocess32_ module instead of the
+   version included with python 2.7.  It is a drop in replacement with
+   better behavior in many situations.
+
    :pep:`324` -- PEP proposing the subprocess module
 
+.. _subprocess32: https://pypi.python.org/pypi/subprocess32/ 
 
 Using the :mod:`subprocess` Module
 ----------------------------------
 
-The recommended approach to invoking subprocesses is to use the following
-convenience functions for all use cases they can handle. For more advanced
-use cases, the underlying :class:`Popen` interface can be used directly.
+The recommended way to launch subprocesses is to use the following
+convenience functions.  For more advanced use cases when these do not
+meet your needs, use the underlying :class:`Popen` interface.
 
 
 .. function:: call(args, *, stdin=None, stdout=None, stderr=None, shell=False)
@@ -57,16 +63,15 @@ use cases, the underlying :class:`Popen` interface can be used directly.
 
    .. warning::
 
-      Invoking the system shell with ``shell=True`` can be a security hazard
-      if combined with untrusted input. See the warning under
-      :ref:`frequently-used-arguments` for details.
+      Using ``shell=True`` can be a security hazard.  See the warning
+      under :ref:`frequently-used-arguments` for details.
 
    .. note::
 
-      Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this function. As
-      the pipes are not being read in the current process, the child
-      process may block if it generates enough output to a pipe to fill up
-      the OS pipe buffer.
+      Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this function
+      as that can deadlock based on the child process output volume.
+      Use :class:`Popen` with the :meth:`communicate` method when you
+      need pipes.
 
 
 .. function:: check_call(args, *, stdin=None, stdout=None, stderr=None, shell=False)
@@ -96,16 +101,15 @@ use cases, the underlying :class:`Popen` interface can be used directly.
 
    .. warning::
 
-      Invoking the system shell with ``shell=True`` can be a security hazard
-      if combined with untrusted input. See the warning under
-      :ref:`frequently-used-arguments` for details.
+      Using ``shell=True`` can be a security hazard.  See the warning
+      under :ref:`frequently-used-arguments` for details.
 
    .. note::
 
-      Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this function. As
-      the pipes are not being read in the current process, the child
-      process may block if it generates enough output to a pipe to fill up
-      the OS pipe buffer.
+      Do not use ``stdout=PIPE`` or ``stderr=PIPE`` with this function
+      as that can deadlock based on the child process output volume.
+      Use :class:`Popen` with the :meth:`communicate` method when you
+      need pipes.
 
 
 .. function:: check_output(args, *, stdin=None, stderr=None, shell=False, universal_newlines=False)
@@ -145,19 +149,16 @@ use cases, the underlying :class:`Popen` interface can be used directly.
 
    .. versionadded:: 2.7
 
-   ..
-
    .. warning::
 
-      Invoking the system shell with ``shell=True`` can be a security hazard
-      if combined with untrusted input. See the warning under
-      :ref:`frequently-used-arguments` for details.
+      Using ``shell=True`` can be a security hazard.  See the warning
+      under :ref:`frequently-used-arguments` for details.
 
    .. note::
 
-      Do not use ``stderr=PIPE`` with this function. As the pipe is not being
-      read in the current process, the child process may block if it
-      generates enough output to the pipe to fill up the OS pipe buffer.
+      Do not use ``stderr=PIPE`` with this function as that can deadlock
+      based on the child process error volume.  Use :class:`Popen` with
+      the :meth:`communicate` method when you need a stderr pipe.
 
 
 .. data:: PIPE
@@ -740,9 +741,9 @@ Replacing :func:`os.system`
 
 ::
 
-   sts = os.system("mycmd" + " myarg")
+   status = os.system("mycmd" + " myarg")
    # becomes
-   sts = call("mycmd" + " myarg", shell=True)
+   status = subprocess.call("mycmd" + " myarg", shell=True)
 
 Notes: