Reverse DNS record check

ptr-check.sh

#!/bin/bash
# v1.0.0 (2023-01-21) cs@fnx.li
HOSTS=(foo.example.org bar.example.com)
SIMPLE=(host1 host2 host3)
SUFFIX=".example.net"

for simple in "${SIMPLE[@]}"
do
	HOSTS+=("${simple}${SUFFIX}")
done

for host in "${HOSTS[@]}"
do
	result=0
	for record in A AAAA
	do
		addrs=$(dig "$record" "$host" +short 2>/dev/null)

		while IFS= read -r addr
		do
			[[ -z "$addr" ]] && continue
			ptr=$(dig -x "$addr" +short 2>/dev/null | sed 's/\.$//g' | sort | uniq)
			check=$(grep -F "$host" <<< "$ptr")
			ptr=$(tr '\n' ' ' <<< "$ptr")
			ptr=${ptr%% }
			result=1

			[[ "$check" != "$host" ]] \
			&& echo "$host [$addr]: MISMATCH ($ptr)" >&2 \
			|| echo "$host [$addr]: OK ($ptr)"
		done <<< "$addrs"
	done

	[[ "$result" -ne 1 ]] && echo "$host: MISSING A/AAAA RECORD!" >&2
done