[Python-Dev] documentation / implementation question for subprocess.check_output

Nick Coghlan ncoghlan at gmail.com
Thu Jul 16 17:27:32 CEST 2015

On 16 July 2015 at 20:35, Guido van Rossum <guido at python.org> wrote:
> In which version? I don't see that phrase in the 3.5 docs.

The equivalent note in 3.x is "Do not use stdout=PIPE or stderr=PIPE
with this function. The child process will block if it generates
enough output to a pipe to fill up the OS pipe buffer as the pipes are
not being read from."

I think Chris is right that it's a docs bug - the warning is
applicable to subprocess.call and subprocess.check_call (which use
Popen.wait), but not to subprocess.check_output (which uses


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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