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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Tue, 13 Nov 2012 09:30:55 -0700
Subject: Re: creating size-limited tar files
To: Python <python-list@python.org>
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On Tue, Nov 13, 2012 at 9:25 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> Sorry, the example I gave above is wrong.  If you're calling
> p1.communicate(), then you need to first remove the p1.stdout pipe
> from the Popen object.  Otherwise, the communicate() call will try to
> read data from it and may "steal" input from p2.  It should look more
> like this:
>
>>>> p1 = subprocess.Popen(cmd1, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
>>>> p2 = subprocess.Popen(cmd2, shell=True, stdin=p1.stdout, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
>>>> p1.stdout = None

Per the docs, that third line should be "p1.stdout.close()".  :-P