How to periodically run a task within emacs?

Question

Is there a way to periodically run an elisp function in a long-running emacs, similar to cron, but within the emacs process?

For example I want to \"automatically ru

Answer 1

Check out run-with-timer.

(run-with-timer 0 (* 30 60) 'recentf-save-list)

Answer 2

You might also find midnight mode useful. One can arbitrarily define 'midnight' and then add hooks as desired.