Print elapsed time in compilation buffer

Question

The compilation buffer prints out start and end date for my compilation. How can I make it also tell me how many minutes & seconds it spent?

I'd like something like: Compilation started at Thu Mar 16 09:10:44 [..] Compilation finished at Thu Mar 16 09:13:04 Compilation took n hours n minutes n seconds

Answer 1

Amazing nobody's answered this yet, but I can't find an answer anywhere. Here's my solution:

(make-variable-buffer-local 'my-compilation-start-time)

(add-hook 'compilation-start-hook #'my-compilation-start-hook)
(defun my-compilation-start-hook (proc) 
  (setq my-compilation-start-time (current-time)))

(add-hook 'compilation-finish-functions #'my-compilation-finish-function)
(defun my-compilation-finish-function (buf why)
  (let* ((elapsed  (time-subtract nil my-compilation-start-time))
         (msg (format "Elapsed: %s" (format-time-string "%T.%N" elapsed t))))
    (save-excursion (goto-char (point-max)) (insert msg))
    (message "Compilation %s: %s" (string-trim-right why) msg)))

Answer 2

I've tweaked above answers with better logic and tested it, working perfectly:

1. Add Hooks to functions:

  (add-hook 'compilation-start-hook 'compilation-started)
  (add-hook 'compilation-finish-functions 'hide-compile-buffer-if-successful)

2. Auto Hide Compile Buffer Delay Customizable Variable (via M-x customize-variable RET auto-hide-compile-buffer-delay):

  (defcustom auto-hide-compile-buffer-delay 0
    "Time in seconds before auto hiding compile buffer."
    :group 'compilation
    :type 'number
  )

3. Get time taken in compilation and use compilation-num-* for warnings and errors count in compilation buffer:

  (defun hide-compile-buffer-if-successful (buffer string)
    (setq compilation-total-time (time-subtract nil compilation-start-time))
    (setq time-str (concat " (Time: " (format-time-string "%s.%3N" compilation-total-time) "s)"))

    (if
      (with-current-buffer buffer
        (setq warnings (eval compilation-num-warnings-found))
        (setq warnings-str (concat " (Warnings: " (number-to-string warnings) ")"))
        (setq errors (eval compilation-num-errors-found))

        (if (eq errors 0) nil t)
      )

      ;;If Errors then
      (message (concat "Compiled with Errors" warnings-str time-str))

      ;;If Compiled Successfully or with Warnings then
      (progn
        (bury-buffer buffer)
        (run-with-timer auto-hide-compile-buffer-delay nil 'delete-window (get-buffer-window buffer 'visible))
        (message (concat "Compiled Successfully" warnings-str time-str))
      )
    )
  )

  (make-variable-buffer-local 'compilation-start-time)

  (defun compilation-started (proc) 
    (setq compilation-start-time (current-time))
  )