Emacs: execute function only after restarting, not after evaluating a buffer

Question

I like to start my work in Emacs with two open windows. For that, I have a function (split-window-horizontally) in my .emacs file.

It works with no problems, splitting window into two side-by-side windows after each evaluation of .emacs buffer. Of course, it also splits window every time I re-evaluate .emacs file to test some new setting. How can I tell emacs not to split the window after each evaluation of .emacs buffer, but rather only after restarting emacs?

I'm looking for something like:

(eval-only-after-restart
    (split-window-horizontally))

Is there any such function? Or another way how to do it?

Answer 1

Like this:

(unless (boundp 'done-split-window-horizontally)
  (split-window-horizontally)
  (setq done-split-window-horizontally t))

Answer 2

Another way:

(add-hook 'emacs-startup-hook #'split-window-horizontally)