os.waitpid doesn't return a tuple containing pid, and its exit status

Question

I try to come up with a workaround for this python bug calling subprocess. I figured the way to go is using os.system in combination with os.waitpid. To test this I wrote the code below. system_call_test.py writes the pid and lot's of text to the file f. But calling os.waitpid() always get me this error: OSError: [Errno 10] No child processes. So I'm having a hard time to check if this construct is working properly. How can I ensure that the script waits for the termination of the other. I'm on windows XP/ python 2.7.

import os
f = r'D:\temp\called.txt'

s = os.system('C:\Python27\python.exe D:\python_spullen\system_call_test.py')
with open(f, 'r') as f_in:
    i = f_in.readline()[-4:]
    print i
    rr = os.waitpid(int(i),0)
    print rr

score 1 · Accepted Answer · edited May 23 '17 at 11:48

1

os.system returns the exit code of the process. So s above is already populated and the process has exited. os.waitpid has nothing to wait on.

edited May 23 '17 at 11:48

Community

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answered Oct 29 '12 at 09:44

Brian Agnew

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So when the exit code is `0`, the process has terminated without errors? – LarsVegas Oct 29 '12 at 09:49

score 1 · Answer 2 · answered Oct 29 '12 at 09:46

1

system() is a combine of fork() + exec() + waitpid(). You should not call waitpid() again.

answered Oct 29 '12 at 09:46

lqs

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os.waitpid doesn't return a tuple containing pid, and its exit status

2 Answers2