Pass value grep command in python - grep

Question

I am obtaining CPU and RAM statistics for the openvpn process by running the following command in a Python script on a Linux Debian 7 box.
>ps aux | grep openvpn
The output is parsed and sent to a zabbix monitoring server.
I currently use the following Python script called psperf.py.
If I want CPU% stats I run: psperf 2
>#!/usr/bin/env python
>
>import subprocess, sys, shlex
>
>psval=sys.argv[1] #ps aux val to extract such as CPU etc #2 = %CPU, 3 = %MEM, 4 = VSZ, 5 = RSS
>
>#https://stackoverflow.com/questions/6780035/python-how-to-run-ps-cax-grep-something-in-python
>proc1 = subprocess.Popen(shlex.split('ps aux'),stdout=subprocess.PIPE)
>proc2 = subprocess.Popen(shlex.split('grep >openvpn'),stdin=proc1.stdout,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
>
>proc1.stdout.close() # Allow proc1 to receive a SIGPIPE if proc2 exits.
>out,err=proc2.communicate()
>
>#string stdout?
>output = (format(out))
>
>#create output list
>output = output.split()
>
>#make ps val an integer to enable list location
>psval = int(psval)
>
>#extract value to send to zabbix from output list
>val = output[psval]
>
>#OUTPUT
>print val
This script works fine for obtaining the data in relation to openvpn. However I now want to reuse the script by passing process details from which to extract data without having to have a script for each individual process. For example I might want CPU and RAM statistics for the zabbix process.
I have tried various solutions including the following but get an index out of range.
For example I run: psperf 2 apache
>#!/usr/bin/env python
>
>import subprocess, sys, shlex
>
>psval=sys.argv[1] #ps aux val to extract such as CPU etc #2 = %CPU, 3 = %MEM, 4 = VSZ, 5 = RSS
>psname=sys.argv[2] #process details/name
>
>#https://stackoverflow.com/questions/6780035/python-how-to-run-ps-cax-grep-something-in-python
>proc1 = subprocess.Popen(shlex.split('ps aux'),stdout=subprocess.PIPE)
>proc2 = subprocess.Popen(shlex.split('grep', >psname),stdin=proc1.stdout,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
>
>proc1.stdout.close() # Allow proc1 to receive a SIGPIPE if proc2 exits.
>out,err=proc2.communicate()
>
>#string stdout?
>output = (format(out))
>
>#create output list
>output = output.split()
>
>#make ps val an integer to enable list location
>psval = int(psval)
>
>#extract value to send to zabbix from output list
>val = output[psval]
>
>#OUTPUT
>print val
Error:
>root#Deb764opVPN:~# python /usr/share/zabbix/externalscripts/psperf.py 4 openvpn
>Traceback (most recent call last):
> File "/usr/share/zabbix/externalscripts/psperf.py", line 25, in <module>
> val = output[psval]
>IndexError: list index out of range
In the past I haven't used the shlex class which is new to me. This was necessary to pipe the ps aux command to grep securely - avoiding shell = true - a security hazard (http://docs.python.org/2/library/subprocess.html).
I adopted the script from: How to run " ps cax | grep something " in Python?
I believe its to do with how shlex handles my request but I`m not to sure how to go forward.
Can you help? As in how can I successfully pass a value to the grep command.
I can see this being benfical to many others who pipe commands etc.
Regards
Aidan

Answer 1

I carried on researching and solved using the following:
!/usr/bin/env python
import subprocess, sys # , shlex
psval=sys.argv[1] #ps aux val to extract such as CPU etc #2 = %CPU, 3 = %MEM, 4 = VSZ, 5 = RSS
psname=sys.argv[2] #process details/name
#http://www.cyberciti.biz/tips/grepping-ps-output-without-getting-grep.html
proc1 = subprocess.Popen(['ps', 'aux'], stdout=subprocess.PIPE)
proc2 = subprocess.Popen(['grep', psname], stdin=proc1.stdout,stdout=subprocess.PIPE)
proc1.stdout.close() # Allow proc1 to receive a SIGPIPE if proc2 exits.
stripres = proc2.stdout.read()
#TEST RESULT
print stripres
#create output list
output = stripres.split()
#make ps val an integer to enable list location
psval = int(psval)
#extract value to send to zabbix from output list
val = output[psval]
#OUTPUT
print val
Regards
Aidan