Delete unused AWS security groups

delete-unused-security-groups.sh

comm -23 <(aws ec2 describe-security-groups --query 'SecurityGroups[*].GroupId' --output text | tr '\t' '\n'| sort) \
  <(aws ec2 describe-instances --query 'Reservations[*].Instances[*].SecurityGroups[*].GroupId' --output text | tr '\t' '\n' | sort | uniq) \
   | tee -a unused-security-groups-in-ec2.txt
   
for x in `cat unused-security-groups-in-ec2.txt`; do echo 'deleting sg: $x' ; aws ec2 delete-security-group --group-id $x; done

WARNING
If you have AWS ECS services with AWSPVC or Fargate launch type and they use the security group, there is no protection, the security group will be removed, leaving the services broken. Unless the services is up and running.