First, you need to have the following line, or a part of it in your sudoers file:
Then, you can set VISUAL or EDITOR to set the default editor for visudo.
By default, visudo chooses vim as the editor, from the following symlinks:
/usr/bin/editor -> /etc/alternatives/editor /etc/alternatives/editor -> /usr/bin/vim.tiny
So you can set /etc/alternatives/editor to another editor:
rm /etc/alternatives/editor ln -s `which emacs` /etc/alternatives/editor
You can set env variables for that session:
export EDITOR="emacs" export VISUAL="emacs"
Joel G Mathew, known in tech circles by the pseudonym Droidzone, is an opensource and programming enthusiast.
His favorite pastime is grappling with GNU compilers, discovering newer Linux secrets, writing scripts, hacking roms, and programs (nothing illegal), reading, blogging. and testing out the latest gadgets.
When away from the tech world, Dr Joel G. Mathew is a practising ENT Surgeon, busy with surgeries and clinical practise.