Parse dnstap.log and get list with only unique subdomains

get-subdomains.shitbash

# Okay.
# It's just a few lines in «shitbash» language.
# Shitbash is awesome! It's great tool for scripts which you run once.
# So... Oh, yeah! You can go fuck yourself if you want say something about quality of this line.

dnstap -r /var/log/knot.tap > /opt/dnstap.log

07:35:58.000000 AQ 0.0.0.0 UDP 42b "domain.tld." IN A
07:35:59.000000 AQ 0.0.0.0 UDP 42b "domain.tld." IN A
07:35:59.000000 AQ 0.0.0.0 UDP 42b "domain.tld." IN AAAA

cat /opt/dnstap.log | grep -iEo '[a-zA-Z0-9-]*\.domain.tld' > /opt/subdomains.txt

accounting.domain.tld
accounting.domain.tld
account.domain.tld
account.domain.tld
accounts.domain.tld

cat /opt/subdomains.txt | sort --unique

accounting.domain.tld
account.domain.tld
accounts.domain.tld

cat /opt/subdomains.txt | sort --unique | grep -iEo '[a-zA-Z0-9-]*\.' | grep -iEo '[a-zA-Z0-9-]*' | grep -v domain

accounting
account
accounts