#!/bin/bash
# Service checking utility
# Requires NetCat
# Run from cron.
# creates a lot of files...sorry
# 2003 William H. Backman
# if you want a log, create an empty "flap.log"

NOTIFY="noc@yourdomain.org"

for SERVICE in \
"mail.yourdomain.org 80" \
"mail.yourdomain.org 22" \

do

# Check to see if a state file exists already
  if [ -f "$SERVICE" ]; then
	STATE=`cat "$SERVICE"`
     else
	STATE="first check"
  fi

# NetCat does the work here.
  nc -z $SERVICE
  if [ $? -eq 0 ]; then
	CATSTATE="success"
	echo $CATSTATE > "$SERVICE"
   else
	CATSTATE="failure"
  	echo $CATSTATE > "$SERVICE"
  fi

# compare the old state to the current
  if [ "$STATE" != "$CATSTATE" ]; then
	echo `date` State change: "$SERVICE" $STATE to $CATSTATE >> flap.log
	echo State change: "$SERVICE" $STATE to $CATSTATE | mail -s "$SERVICE $CATSTATE" $NOTIFY 
  fi

done