Avoiding defunct processes

[Richard]

Hello,

I create child processes with subprocess.Popen().
Then I either wait for them to finish or kill them.
Either way these processes end up as defunct until the parent process
completes:
$ ps e
6851 pts/5 Z+ 1:29 [python] <defunct>

This confuses another library as to whether the processes are
complete.
For now I detect which processes are defunct by parsing the output of
"ps".
What would you recommend? I am hoping there is a cleaner way.

Richard

 

[Chris Angelico]

Hello,

I create child processes with subprocess.Popen().
Then I either wait for them to finish or kill them.
Either way these processes end up as defunct until the parent process
completes:
$ ps e
6851 pts/5 Z+ 1:29 [python] <defunct>

This confuses another library as to whether the processes are
complete.
For now I detect which processes are defunct by parsing the output of
"ps".
What would you recommend? I am hoping there is a cleaner way.

That's a zombie process, it's finished but the parent hasn't wait()ed
for it yet.

http://docs.python.org/3.3/library/subprocess.html#subprocess.Popen.wait

Once the process has ended, call that to get its return value and
clean everything up.

ChrisA

 

[Nobody]

I create child processes with subprocess.Popen().
Then I either wait for them to finish or kill them.
Either way these processes end up as defunct until the parent process
completes:
$ ps e
6851 pts/5 Z+ 1:29 [python] <defunct>

You need to either call the .wait() method, or keep calling the .poll()
method until the .returncode attribute is not None.