Email Alerts when service or server automatically comes up - bash

Question

I am working on a bash script that helps to ping and get the network interface level status of the host machines and services.
This script will send a email alerts in case of failure.
#!/bin/bash
HOSTS="192.168.8.200"
COUNT=4
for myHost in $HOSTS
do
count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
if [ $count -eq 0 ]; then
# 100% failed
echo -e "HOST:$myHost is down (ping failed) at $(date)" | mailx -A gmail -s “Mail subject” anymail#anydomain.com
fi
done
This works fine.
But need help to get a one single email alert when host automatically comes up (ping success).

Answer 1

You need to save the state of the host (up/down) during the calls of your script.
if the host is "up" and the former state was "down" then you need to send an email.
You can just write the result of the "check command" to a file in /tmp/
if the check returns that the server is up you read the content of the file. if the state is "down" in the file, then send an email an write "up" to the file.
on the next check if the server is up, there will be no additional email sent, because the server was also "up" before.
#!/bin/bash
HOSTS="192.168.8.200 192.168.8.201 192.168.122.1"
COUNT=4
STATE="/tmp/ping_state.txt"
for myHost in $HOSTS
do
count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
if [ $count -eq 0 ]; then
# 100% failed
#echo -e "HOST:$myHost is down (ping failed) at $(date)" | mailx -A gmail -s “Mail subject” anymail#anydomain.com
echo "host $myHost down"
#delete all previous entries of that ip
sed -i "/$myHost/d" $STATE
#mark host as down
echo "$myHost - down" >> $STATE
else
CHECK=`grep "$myHost" $STATE | grep -o "down"`
if [ "$CHECK" = "down" ]; then
echo "host $myHost up again"
#insert email for host up here
fi
#delete all previous entries of that ip
sed -i "/$myHost/d" $STATE
echo "$myHost - up" >> $STATE
fi
done
for simple testing I just used an echo statement instead of sending an email.