The simple case is like this:

You want to change a config file using vim, and after you edit, you got a permission problem, you don't have the permission.

So how to keep the current edit and save the change, the simple command is :w !sudo tee %.

Explanation as below:

:w – Write a file (actually buffer).
!sudo – Call shell with sudo command.
tee – The output of write (vim :w) command redirected using tee.
% – The % is nothing but current file name.

But what about Emacs, how do we do this in Emacs, we also got one:

C-x C-f /sudo::/path/to/file

It uses Tramp module to do the same thing.

#vim #emacs