reverse_dns_checker.sh

#!/usr/bin/env bash

for item; do
  entries=$(dig ${item} +short ANY)
  if [ -z "${entries}" ]; then
    echo -e "No A or AAAA entries returned for ${item}"
  else
    for entry in ${entries}; do
      reverse_entry=$(dig +short -x "${entry}")
      if [ -z "${reverse_entry}" ]; then
        echo -e "ERROR: ${item} - Missing reverse entry for ${entry}"
      elif [ "${reverse_entry}" != "${item}." ]; then
        echo "WARNING: ${item} - Doesn't match reverse entry ${reverse_entry}"
      else
        echo "OK: ${item} - DNS Forward/Reverse Correct"
      fi
    done
  fi
done