Re: Is there a command to auto-purge old eln-cache files?

[Eli Zaretskii <eliz@gnu.org>]

> From: Kaushal Modi <kaushal.modi@gmail.com>
> Date: Fri, 24 Jun 2022 16:33:58 -0400
> 
> I routinely update my emacs build from git and over time, and so I
> collect hundreds of MBs of eln-cache files. Just looking at the
> eln-cache dir names, it's not very evident which one is the latest one
> (especially, from a tool call ncdu, I cannot tell which directories
> should be safe to delete).

If you keep only one Emacs executable for all those builds, and either
delete the old ones or don't care whether they remain usable, then you
can identify the only subdirectory under the eln-cache directory you
need to keep by one of the following methods:

 . sort the directories under ~/.emacs.d/eln-cache by date, and leave
   only the one whose time stamp is the latest
 . ask Emacs: "M-: comp-native-version-dir RET" -- you can delete all
   the subdirectory of eln-cache except the one whose name that
   produces

> So that made me wonder if there's already an emacs-lisp function to
> purge old eln caches, and I am not aware?

Define "old" for this purpose.

E.g., I keep many old Emacs executables (it makes it easier to bisect
bugs), so for me "old" means "belonging to an Emacs executable I
removed".