Emacs Uptime

Since I tend to work in Emacs no matter what computer I’m using, I got curious after reading Steve Yegge’s latest post about XEmacs instability what exactly my uptimes are on all my Emacs sessions (I use GNU Emacs, but I was still curious). This is some elisp I threw together to answer that question.

(require 'cl)

(defun duration (time)
  "Takes in a time-value and returns the number of seconds since
   the epoch that value represents."
  (+ (* 65536 (car time)) (cadr time)))

(defun uptime ()
  "Prints the current uptime of Emacs as recorded on startup in
   the value 'start-time'"
  (interactive)
  (let* ((total (duration (time-subtract (current-time) start-time)))
         (days  (floor (/ total 86400)))
         (hours (progn (decf total (* days  86400)) (floor (/ total 3600))))
         (mins  (progn (decf total (* hours 3600))  (floor (/ total 60))))
         (secs  (progn (decf total (* mins  60))    (floor total))))
    (message "%d days, %d hours, %d minutes, %d seconds" days hours mins secs)))

; Put this in your .emacs
(setq start-time (current-time))