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?

One problem is that when somebody runs 6 arbitrary sudo commands matching your greps, your script will not be restarted. — Graipher
– Graipher, Commented Mar 21, 2018 at 11:38
Does the python process need to be running constantly, or is it enough to invoke it at a certain (higher frequency) interval? How fast does it have to restart to fulfil its purpose? — frostell
– frostell, Commented Mar 21, 2018 at 11:43
ps aux| grep abc| grep def| grep sudo if abc is program_name — aja
– aja, Commented Mar 21, 2018 at 11:43
It has to be running all the time without any stop. If it stops it needs to be restarted as soon as possible. — aja
– aja, Commented Mar 21, 2018 at 11:46

frostell · Accepted Answer · 2018-03-21 12:32:22Z

6

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)

edited Mar 21, 2018 at 12:32

answered Mar 21, 2018 at 12:14

frostell

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1 Comment

frostell Over a year ago

if you put it in a cronjob it will get activated automatically on reboot though the cronjob regardless of where you put the script - is that what you're after?

Jiri Kapoun · Accepted Answer · 2018-03-21 12:27:28Z

3

How about making it a service? A very clean solution, in my opinion.

For more information on how to do it, you can read this article.

answered Mar 21, 2018 at 12:27

Jiri Kapoun

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