I need to restore the *scratch* buffer from the last time I used emacs even though I killed it and had to restart

Question

I was using emacs (XEmacs actually) and using the scratch buffer to experiment with regular expressions for a regex-replace operation that was giving me trouble. That has nothing to do with the problem, just setting the context.

A power failure caused me to have to reboot my computer and restart emacs. Because scratch can't be saved without explicitly copying it to a file, it's gone.

Is there any way to recover the previous (before the power failure) contents of scratch and, if so, how do I do it?

I'm not looking for suggestions for how to prevent this from being a problem in the future---I've figured that out. I just want restore the scratch contents that I just lost, if possible.

Answer 1

Buffers that are not saved to a file are just kept in memory. The contents of memory are lost on a reboot¹, so these buffers are gone. If you had a core dump, or a copy of your memory (such as you might get if you suspended your computer to disk), then perhaps you could recover it. Otherwise, no.

¹ Technically memory can remain readable for a few minutes without power if you freeze the ram using propellant from a can of compressed air, liquid nitrogen, or some other means. But you’re probably not set up for that on short notice.

Answer 2

You can use https://github.com/Fanael/persistent-scratch to persist the scratch buffer across emacs sessions. I save it to the no-littering var directory.

(use-package persistent-scratch
  :after no-littering
  :custom
  (persistent-scratch-save-file (no-littering-expand-var-file-name "scratch"))
  :config
  (persistent-scratch-setup-default))