dns name sever query comparison

nsq_compare.sh

nameserver_source="a.iana-servers.net"
nameserver_comparison="b.iana-servers.net"
dns_records="
example.com a
ftp.example.com a
mail.example.com a
ns1.example.com a

www.example.com cname

example.com mx

example.com txt

example.com ns

example.com soa
"


source_output=""
comparison_output=""
NEWLINE=$'\n'
while read domain
do
  source_output+="$(dig +nocmd +noall +answer @${nameserver_source} ${domain} | grep -v "^;")${NEWLINE}"
  comparison_output+="$(dig +nocmd +noall +answer @${nameserver_comparison} ${domain} | grep -v "^;")${NEWLINE}"
done <  <(echo "${dns_records}")

echo "${source_output}"
echo "${comparison_output}"

Ran into this not outputting anything for NS records on sub-domains, adding +authority to the query when an NS record is being looked up solves the issue. The use case being Dotmailer NS records on something like events.example.com. Added these lines in my forked copy of the script: https://gist.github.com/davidalger/a33891d3a2e6858f3a8987bb7f1ab062#file-nsq_compare-sh-L33-L35