I'd like to use vi (
set -o vi can do the trick) as default in my shell instead of emacs, but I do not want to put it into bash startup scripts.
Why? Because I work as verification engineer and I am using several user accounts, which are also quite often reinstalled. Changing of default profile is not answer too, because some of software creates its own home directory (independent on default profile).
EDIT: I know you gave me several ways how to do it at startup or anytime, but I do want to change it somewhere in system and have it as default, is this possible?