cat  ip_list.txt192.168 .1.1
192.168 .1.2
SECURITY_GROUP_ID = "sg-0f08237289xxxxx" 
IFS = ' '  read  -ra  INTERNAL_IPS <<<  $( cat  ip_list.txt) for  IP  in  "${INTERNAL_IPS[ @] } " 
do INSTANCE_ID = $( aws ec2 describe-instances --filters  "Name=private-ip-address,Values=$IP "  --query  'Reservations[].Instances[].InstanceId'  --output  text) if  [  !  -z  "$INSTANCE_ID "  ] then CURRENT_SECURITY_GROUPS = $( aws ec2 describe-instances --instance-ids $INSTANCE_ID --query  'Reservations[].Instances[].SecurityGroups[].GroupId'  --output  text) NEW_SECURITY_GROUPS = "$CURRENT_SECURITY_GROUPS  $SECURITY_GROUP_ID " echo  "Adding security groups $NEW_SECURITY_GROUPS  to instance $INSTANCE_ID " aws ec2 modify-instance-attribute --instance-id $INSTANCE_ID  --groups  $NEW_SECURITY_GROUPS else echo  "No instance found with internal IP $IP " fi 
done