Calling a subprocess in python with environmental variables

Question

I am trying to write a python script to automatically scan a section of plex using the Plex Media Scanner. To do so, I must run the scanner as the user running plex (in this case it is 'plex') as well as provide it with the environment variable 'LD_LIBRARY_PATH'. I've tried using both subprocess.call and subprocess.Popen with no difference. In either case, I am not getting any output. Here is the code I am using:

#!/usr/bin/python
import os
import subprocess
import shlex

env = os.environ.copy()
env['LD_LIBRARY_PATH'] = '/usr/lib/plexmediaserver'
s = "/bin/su - plex -c '/usr/lib/plexmediaserver/Plex\ Media\ Scanner -s -c 2'"
task = shlex.split(s)
exitCode = subprocess.call(task, env=env, shell=True)

Now I already have a working version that does what I want it to do but I had to resort to using a wrapper bash script to do so. You can see the code below:

#!/bin/sh
export LD_LIBRARY_PATH=/usr/lib/plexmediaserver
/usr/lib/plexmediaserver/Plex\ Media\ Scanner $@

And the relevant line of the script which calls it:

exitCode = subprocess.call("/bin/su - plex -c '/var/lib/deluge/delugeScripts/pms.sh -s -c 2'", shell=True)

Thanks for your help.

I doubt that it matters, but why shell=True in the first code snippet? — mgilson
– mgilson, Commented Jan 7, 2014 at 5:29
@mgilson This was just one of the different variations I've tried. I've been at it for quite a while so things got mixed together. It's strange because when I print env it has the variable but then the scanner still complains that it can't find the libraries it needs. — pyarmak
– pyarmak, Commented Jan 7, 2014 at 5:32
@pyarmak the - in su makes it a login shell which re-initializes the environment. — jordanm
– jordanm, Commented Jan 7, 2014 at 5:40
@jordanm Oh dear I completely missed that. Thank you very much. It works perfectly now. — pyarmak
– pyarmak, Commented Jan 7, 2014 at 5:44

pyarmak · Accepted Answer · 2014-01-07 05:45:32Z

1

As jordanm noted in his comment:

the - in su makes it a login shell which re-initializes the environment.

answered Jan 7, 2014 at 5:45

pyarmak

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