Python script won't start via bash

Question

I have this bash script that start the python script ms.py What is the problem here ?

#!/bin/bash
if [ $(ps aux | grep -e 'ms.py$' | grep -v grep | wc -l | tr -s "\n") -eq 0 ]; 
then python /root/folder/ms.py &
fi

and this in my crontab

*/1 * * * * /root/folder/script.sh

When I start the script manually it works normal.

• sberry: I would make sure your cron user has the necessary programs in the PATH, starting with Python. Perhaps /full/path/to/python /root/folder/ms.py
• Vor: I would check the permissions
• Mycha: I'm trying to do this with putty. Permissions are ok.
• Mikko Ohtamaa: What does your cron debug output says? By default it should email to root@localhost?

Answer 1

you are testing the output of that pipeline against the number zero. I assume you want to start your python program only if it's not already running:

pid=$(pgrep -f 'ms.py$')
if [[ $pid ]] && kill -0 $pid; then
 echo already running
else
 echo not running
 python /root/folder/ms.py &
fi

• nandhp: [[ $pid ]] should be [[ "$pid" ]]. The former won't work if pgrep doesn't match -- it will become [[ ]], which is a syntax error.
• glenn jackman: @nandhp, not in bash: the double brackets are smart enough to avoid that trap: x=""; [[ $x ]] && echo y || echo n