New submission from Martin Panter:
The documentation for the “subprocess” module says that a “with” statement will
“wait for” the process, implying that it does not leave a zombie. However this
is not the case if there is buffered input data:
$ python3 -Wall -bt -q
>>> import subprocess
>>> with subprocess.Popen(("true",), stdin=subprocess.PIPE, bufsize=-1) as p:
... from time import sleep; sleep(1) # Wait for pipe to be broken
... p.stdin.write(b"buffered data")
...
13
Traceback (most recent call last):
File "<stdin>", line 3, in <module>
File "/usr/lib/python3.4/subprocess.py", line 899, in __exit__
self.stdin.close()
BrokenPipeError: [Errno 32] Broken pipe
>>> # (Hit Ctrl-Z here)
[1]+ Stopped python3 -Wall -bt -q
[Exit 148]
$ ps
PID TTY TIME CMD
15867 pts/5 00:00:00 python3
15869 pts/5 00:00:00 true <defunct>
15873 pts/5 00:00:00 ps
32227 pts/5 00:00:10 bash
Similarly, calling Popen.communicate() does not clean the process up either if
there is buffered input data and the process has already exited. The
documentation does not spell out how a broken pipe is handled in communicate(),
but after reading Issue 10963 I see that in many other cases it is meant to be
ignored.
The best way to clean up a subprocess that I have come up with to close the
pipe(s) and call wait() in two separate steps, such as:
try:
proc.stdin.close()
except BrokenPipeError:
pass
proc.wait()
----------
components: Library (Lib)
messages: 219450
nosy: vadmium
priority: normal
severity: normal
status: open
title: Cleaning up a subprocess with a broken pipe
versions: Python 3.4
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Python tracker <[email protected]>
<http://bugs.python.org/issue21619>
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