This is a small tip if you want to remove a line from a file, this is particularly useful when you get this message:
Warning: the ECDSA host key for 'garron.me' differs from the key for the IP address '126.96.36.199' Offending key for IP in /home/gentoo/.ssh/known_hosts:20 Matching host key in /home/gentoo/.ssh/known_hosts:48 Are you sure you want to continue connecting (yes/no)?
So in this case I may use this command:
sed -i 20d ~/.ssh/known_hosts
You can use it in other situations as well.