Script to detect and report if Service has changed started/stopped

Question

I am trying to write a bash script that detects if a service has changed state. I have this so far:

while true; do
     if [ -z "$(netstat -tulpn | grep 51827)" ];
     then
         echo notinuse
     else
         echo inuse
     fi
sleep 5
done

It works but it will endlessly write when the service is up or down, and I only want it to report on the first instance of a state change. So report when the service was down, and then up as well as when it was up and then went down.

I started to create loop counters and comparing to a previous run but I got into a complete mess of variables. Can anyone help?

Answer 1

if [ -z "$(netstat -tulpn | grep 51827)" ];
     then

         echo notinuse
         notify_status="notinuse-sent"
         

     else
         echo inuse
         notify_status="inuse-sent"
         
     fi


while true; do
     if [ -z "$(netstat -tulpn | grep 51827)" ];
     then
         if [ $notify_status = "notinuse-sent" ]; then
               echo "already notified"
         else
               echo notinuse
               $notify_status="notinuse-sent"
         fi
         
         
         

     else
         if [ $notify_status = "inuse-sent" ]; then
               echo "already notified"
         else 
               echo inuse 
               $notify_status="inuse-sent"
         fi

         
     fi
sleep 5
done