Terminology

Buffer When you open a file in emacs, it creates a buffer to visit that file. Frame This is what I call a floating window. Emacs had a different meaning for window. Window It is that space on the screen or view that shows you the buffer. It might be that multiple buffers are open but only a few windows are showing those buffers.

Buffer

Open a file in the current buffer

;; fn -> f -> b!
(find-file "/tmp/..")

Open a file in another buffer

(switch-to-buffer-other-window b)                             ;; same buffer in another window
(switch-to-buffer-other-window (current-buffer))              ;; same buffer in another window
(switch-to-buffer-other-window (find-file-noselect filename)) ;; a file in another windoe

Is buffer visible?

;; fn -> b -> w
(get-buffer-window b)

Get the buffer that is visiting a file Is there any buffer visiting a file?

;; fn -> f -> b
(get-file-buffer filename) ;; returns nil if none exists

You can create a buffer for a file if it doesn’t exist (and then get-file-buffer will return the buffer):

;; fn -> f -> b
(find-file-noselect filename)

Show the file in another window

If any buffer is visiting a file, show that buffer in another window, otherwise, create a buffer and show it in another window.

(let ((b (get-file-buffer filename)))
  (if b (switch-to-buffer-other-window b)
    (switch-to-buffer-other-window (find-file-noselect filename))))

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• Tag: emacs