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Python wait () subprocess behaves differently on mavericks and Yosemite

I recently upgraded to Yosemite. And some Python scripts hang, which was used to work with Mavericks. My version is 2.7.8. I created a test case:

import subprocess
cat = subprocess.Popen(['top', '-l', '1'],
                            stdout=subprocess.PIPE,
                            )
cat.wait()

Powered by Maverics, but hangs on Yosemite. When I interrupt Yosemite, I see the following traceback.

Traceback (most recent call last):
    File "test.py", line 5, in <module>
      cat.wait()
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1376, in wait
      pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 476, in _eintr_retry_call
      return func(*args)
    KeyboardInterrupt

Any hint as to what I am doing wrong?

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1 answer


It looks like you need to call communicate()

. From Python documentation :



Popen.wait()

Wait for the child process to complete. Set and return the attribute returncode

.

Warning: This will stall when used stdout=PIPE

and / or stderr=PIPE

, and the child process generates enough output to the pipe so that it blocks waiting for the OS buffer to receive more data. use communicate()

to avoid it.

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