[Python-checkins] r65469 - python/trunk/Doc/library/subprocess.rst

gregory.p.smith python-checkins at python.org
Mon Aug 4 03:03:51 CEST 2008


Author: gregory.p.smith
Date: Mon Aug  4 03:03:50 2008
New Revision: 65469

Log:
issue1606: Add warnings to the subprocess documentation about common pitfalls
of using pipes that cause deadlocks.


Modified:
   python/trunk/Doc/library/subprocess.rst

Modified: python/trunk/Doc/library/subprocess.rst
==============================================================================
--- python/trunk/Doc/library/subprocess.rst	(original)
+++ python/trunk/Doc/library/subprocess.rst	Mon Aug  4 03:03:50 2008
@@ -193,6 +193,10 @@
    Wait for child process to terminate.  Set and return :attr:`returncode`
    attribute.
 
+   warning:: This will deadlock if the child process generates enough output
+   to a stdout or stderr pipe causing it to block waiting for the OS's pipe
+   buffer to accept more data.
+
 
 .. method:: Popen.communicate(input=None)
 
@@ -250,18 +254,30 @@
    If the *stdin* argument is ``PIPE``, this attribute is a file object that
    provides input to the child process.  Otherwise, it is ``None``.
 
+   warning:: Use :meth:`communicate` rather than .stdin.write() to avoid
+   deadlocks due to any of the other pipe buffers filling up and blocking the
+   child process.
+
 
 .. attribute:: Popen.stdout
 
    If the *stdout* argument is ``PIPE``, this attribute is a file object that
    provides output from the child process.  Otherwise, it is ``None``.
 
+   warning:: Use :meth:`communicate` rather than .stdout.read() to avoid
+   deadlocks due to any of the other pipe buffers filling up and blocking the
+   child process.
+
 
 .. attribute:: Popen.stderr
 
    If the *stderr* argument is ``PIPE``, this attribute is file object that
    provides error output from the child process.  Otherwise, it is ``None``.
 
+   warning:: Use :meth:`communicate` rather than .stderr.read() to avoid
+   deadlocks due to any of the other pipe buffers filling up and blocking the
+   child process.
+
 
 .. attribute:: Popen.pid
 


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