[issue7177] Unclear warning for subprocess.call

[Christopher Jefferson]

New submission from Christopher Jefferson <chris at bubblescope.net>:

I wandered across subprocess.call as it was mentioned as a replacement for os.system. The 
following large warning is attached to it:

Warning Like Popen.wait(), this will deadlock if the child process generates enough output to a 
stdout or stderr pipe such that it blocks waiting for the OS pipe buffer to accept more data.

This scared my off completely, and I assumed the function was simply broken, as I assumed 
"stdout pipe" just meant that wherever stdout was sent by default.

I now believe this warning only applies if 'stdout=PIPE', or similar, is used explicitally.

Could this warning be better worded, perhaps adding "if stdout or stderr are explicitly 
redirected", as in:

Warning Like Popen.wait(), if stdout or stderr are explicitly redirected this will deadlock if 
the child process generates enough output to a stdout or stderr pipe such that it blocks 
waiting for the OS pipe buffer to accept more data.

----------
assignee: georg.brandl
components: Documentation
messages: 94297
nosy: azumanga, georg.brandl
severity: normal
status: open
title: Unclear warning for subprocess.call
versions: Python 3.1

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue7177>
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