#!/bin/sh
REC=ucheck.domain

NS="a b c d"
HO=.ns.domain

time=$(date +%s)

for n in $NS; do
  n="$n$HO"
  res=$(dig @$n +short TXT $REC | sed 's/"//g')

  if [ -z "$res" -o "${res%[a-z]}" != "${res}" ]; then
    echo "Bad $n"
  elif [ "$res" -lt "$[$time - 600]" ] 2>/dev/null; then
    echo "Bad $n"
  fi
done