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 \
	-u root \
	-Be "SHOW GLOBAL STATUS LIKE 'Slave_running'" | \
	tail -n1 | grep -Pqe "^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