This will check the A record both for the provided NameServer and for the domain's own NameServer.

checkDNS.sh

#!/bin/sh
#
# This will check the A record both for the provided NameServer
#  and for the domain's specified NS
#

if [ "$1" = "--help" -o "$1" = "-h" ]; then
  echo "\nUsage:"
  echo "$0 \$NS_IP domain1.tld domain2.tld ..."
  echo "Example: $0 8.8.8.8 google.com example.com\n"
  return 0;
fi;

myNS="$1"
domains="${@:2}"

echo "Checking domains: $domains"
echo "Using as my NS: $myNS"

for dom in "$domains"; do
  domNS="$(dig +short "$dom" NS | head -n1)"

  if [ ! -z "$domNS" ]; then
    echo "#\n#\tAsking for $dom\n#"
    echo "\n NS: $names"
    dig "@$domNS" +noall +answer "$dom" A
  else
    echo "\n#\tERROR: Missing domain name server or domain not existent"
  fi

  echo "\n Asking my NameServer"
  dig +noall +answer "$dom" A
  dig +noall +answer "www.$dom" A
done;