Get the last line of an iteration

I've created a simple script that runs nslookup for the configured IPs. It will run 10x (per requirement) to validate if it's pointed to the active IP and then email an alert if it returns inactive.

Script is working perfectly, however, when it alerts, it does it 10x due to the loop. How do I get just the last line if it does not satisfy the condition so that it will only send one email per IP?

Code below:

CDC="456.22." 
PDC="123.11" 
ACTIVE_DC=$CDC 
#ACTIVE_DC=$PDC 



#ADD/REMOVE VIRTUAL IPs HERE
vIP="app1.app.com app2.app.com"
[email protected]
subject="[TEST - - CRITICAL WARNING] NETWORK TRAFFIC POINTING TO INACTIVE DATA CENTER"
DATE=$(date ' %Y-%m-%d %H:%M:%S')

echo ""
echo "########################################################################"
echo "#################################START##################################"

for IP in $vIP; do
    echo""
    app_name=$(nslookup $IP | awk 'NR==4 {print NR,$0}' | cut -c 9-50) #Prints each VIP
    echo "$app_name"
        for i in {1..10}; do #Runs nslookup 10x for each VIP
            current=$(nslookup $IP | awk 'NR==5 {print NR,$0}' | cut -c 12-30)
            current2=$(echo "$current" | cut -c 1-6)
            echo "$current"
            if [[ "$current2" == "$ACTIVE_DC" ]]; then
                echo "Traffic is pointing to active DC"
            else
                echo "ERROR Traffic is pointing to INACTIVE DC"
                echo "$DATE - [TEST] CRITICAL - NETWORK TRAFFIC POINTING TO INACTIVE DATA CENTER
                CHECK $app_name
                TRAFFIC POINTING TO $current
                TRAFFIC SHOULD BE POINTING to $ACTIVE_DC ONLY!
                " | mailx -s "$subject" -r $MAIL_FROM [email protected]
            fi
        done
done

CodePudding user response：

Modified script:

#!/bin/bash

CDC="456.22." 
PDC="123.11" 
ACTIVE_DC=$CDC 
#ACTIVE_DC=$PDC 

#ADD/REMOVE VIRTUAL IPs HERE
vIP="app1.app.com app2.app.com"
[email protected]
subject="[TEST - - CRITICAL WARNING] NETWORK TRAFFIC POINTING TO INACTIVE DATA CENTER"
DATE=$(date ' %Y-%m-%d %H:%M:%S')

echo ""
echo "########################################################################"
echo "#################################START##################################"

for IP in $vIP; do
    sendemail='false'
    echo ""
    app_name=$(nslookup "$IP" | awk 'NR==4 {print NR,$0}' | cut -c 9-50) #Prints each VIP
    echo "$app_name"
    
    for i in {1..10}; do #Runs nslookup 10x for each VIP
        current=$(nslookup "$IP" | awk 'NR==5 {print NR,$0}' | cut -c 12-30)
        current2=$(echo "$current" | cut -c 1-6)
        echo "$current"
        if [[ "$current2" == "$ACTIVE_DC" ]]; then
            echo "Traffic is pointing to active DC"
        else
            sendemail='true'
            echo "ERROR Traffic is pointing to INACTIVE DC"
            break
        fi
    done
    
    if [[ "$sendemail" == 'true' ]]
    then
        echo "$DATE - [TEST] CRITICAL - NETWORK TRAFFIC POINTING TO INACTIVE DATA CENTER
        CHECK $app_name
        TRAFFIC POINTING TO $current
        TRAFFIC SHOULD BE POINTING to $ACTIVE_DC ONLY!
        " | mailx -s "$subject" -r $MAIL_FROM [email protected]
    fi
done

What I added is:

variable sendemail is set to false at the beginning of every for loop on IP addresses.
If there is an error, the email must be sent, so set the sendemail variable to true and break out of the for i ... loop.
If the sendemail is true, send the email. It will now happen only once per IP, since the email sending code is outside the nslookup 10X loop.