Example bash script for a PRTG SSH script sensor - this one for MySQL slave to master checks.

mysqlslavecheck.sh

#!/bin/bash

# query MySQL for slave replication status
# note: requires [~/.my.cnf] to be present a populated with valid MySQL password
mysql \
	--batch \
	--user root \
	--execute "SHOW GLOBAL STATUS LIKE 'Slave_running';" | \
		tail --lines 1 | grep --extended-regexp --quiet "^Slave_running\tON$"

if [[ $? -eq 0 ]]; then
	# success
	echo "0:100:Slave connected to master"
else
	# failure
	echo "2:0:Slave disconnected from master"
fi