Can I run shell/bash script?

FastCron needs your web server to execute the script, it couldn’t run a shell script directly.

If you’re using PHP, please check if your hosting allows exec or shell_exec, then create a cron script to run the bash script like this:

/home/example.com/public_html/cron.php

echo shell_exec('/home/example.com/shell/backup.sh');

Once you confirm that the script can be triggered by visiting the URL
https://example.com/cron.php
with your browser, you can create a cron job to run script.

Most shared hosting providers disable those functions, so you won’t be able to run shell/bash script with FastCron.