Restart python script automatically even when it crashes in Linux

Question

I have a python program that has to be running all the time. If for some reason it was stopped I want to restart it automatically. I thought of having a cron that will run every n number of seconds and check the program is running. My shell script is looks like this:

#!/usr/bin/env bash
CM_COMMAND=`ps aux| grep abc| grep def| grep sudo`
LEN_COMMAND=${#CM_COMMAND}
if[["$LEN_COMMAND" -le "5"]] 
then
    echo "start the python program"
fi
exit

When I run this script I am getting the error: my_prog.sh: line 4: $'if[[118\r -le 5]]\r': command not found'

What is the alternative of doing this and what is the problem with my script?

Answer 1

Maybe this would be more robust?

1) save the PID of your process when you start it with:

{your_python_command} & echo $! >>/{some_folder}/your_app.pid

2) This script will check and restart if it can't find the PID..

#!/usr/bin/env bash

PID=`cat /{some_folder}/your_app.pid`

if ! ps -p $PID > /dev/null
then
  rm /{some_folder}/your_app.pid
  {your_python_command} & echo $! >>/{some_folder}/your_app.pid
fi

3) To add it to a cronjob:

crontab -e

choose your text editor and add this row at the end of the file:

*/1 * * * * /{your_path}/{your_script_name}

exit and save

(this will run the script every minute, check crontab manual to set your exact interval)