Sample code for cron job automation ( Create a certbot auto-renewal cron job )

cronjob_automation.sh

#!/bin/bash

# If our cron job already exists, bail out.
if ! crontab -l &> /dev/null | grep -q "/usr/bin/certbot renew"; then
    # Copy the existing cron jobs into a temporary file
    crontab -l &> /dev/null > cronjobs.txt
    # Add our new cron job to the file
    echo "15 3 * * * /usr/bin/certbot renew --quiet" >> cronjobs.txt
    # Replace content of current user crontab with the content from our cron jobs file
    cat cronjobs.txt > /var/spool/cron/crontabs/"$USER"
    # Remove the temporary file
    rm cronjobs.txt 
fi