Checks if the name servers of a domain are changed.

dns-ns-is-not.sh

#!/usr/bin/env sh
#
# Checks if the nameservers of a domain changed.
#
# Example:
# $ dns-ns-is-not example.org auto.dns.br \
#      && send-to-room.sh "DNS change applied! \o/"

DIG=$(command -v dig)
DNS="8.8.8.8"
DOMAIN=${1:-""}
PATTERN=${2:-""}
WAIT_SECONDS=60

if [ ! -z "$DEBUG" ]
then
	set -x
fi

if [ -z "$DIG" ]
then
	echo "Error: dig is not installed." 2>&1
	exit 2
fi

display_help()
{
	cat <<-EOT
	Usage: $APP_NAME <domain> <pattern>

	Will check the name servers of a domain, every 10 seconds, so
	the pattern is not found. Exits with 0 (zero) once the pattern
	is not found anymore.
	EOT
}

remove_leading_spaces()
{
	sed 's/^[ ]*//g'
}

count_lines()
{
	wc -l
}

check_pattern_in_domain()
{
	domain="$1"
	pattern="$2"

	now=$(date)
	lines_found=$($DIG @"$DNS" +short NS "${DOMAIN}" | grep "$PATTERN" | count_lines | remove_leading_spaces)
	if [ $lines_found -gt 0 ]
	then
		sleep $WAIT_SECONDS
		echo "[${now}] Pattern found, retrying in ${WAIT_SECONDS} seconds..."
		check_pattern_in_domain "${domain}" "${pattern}"
	else
		return 0
	fi
}

if [ -z "$DOMAIN" ] || [ -z "$PATTERN" ]
then
	display_help
	exit 1
fi

check_pattern_in_domain "${DOMAIN}" "${PATTERN}"
exit 0
# vim: ft=sh sw=4 ts=4 ai noet: