Can I gain root permission without leaving vim?

Question

Sometimes when I edit a file which require root permission (e.g. files under /etc), but I forget run vim as sudo.

After edit finished, and type :wq to save

Answer 1

To force a save use the following command

:w !sudo tee %

It will prompt you for your password.

Answer 2

The mentioned trick with tee is nice; if you need this often I'd recommend the SudoEdit plugin, which offers a :SudoWrite command (and even a sudo: protocol handler).