monitor dns response, alert when it changes

dns-response-check.sh

#!/bin/bash
declare -A currentAnswer=()
declare -A lastAnswer=()
while getopts ":s" opt; do
        case $opt in
                s) silent=true ;;
        esac
done
shift "$((OPTIND-1))"
query=${1:-"autodiscover.wip.company.com."}

while :; do
        #hr;
        date '+%F %T.%N %Z';
        for resolver in geodns1-int.company.com. geodns2-int.company.com.; do
                varResolver=${resolver%%-*}
                currentAnswer[$varResolver]="$(dig @${resolver} ${query} +short | tail -1)"
                printf 'QUERY: %s .. RESOLVER: %s .. ANSWER: %s\n' "${query}" "${resolver}" "${currentAnswer[$varResolver]}"
                if [[ "${currentAnswer[$varResolver]}" != "${lastAnswer[$varResolver]}" ]]; then
                        [[ "$silent" == "true" ]] || printf '^G'
                        printf '%s\n' 'This answer differs from the last!'
                fi
                lastAnswer[$varResolver]="${currentAnswer[$varResolver]}"
        done
        sleep 10;
done