Elisp: Buffer Functions

By Xah Lee. Date: . Last updated: .

Here's the most useful functions for buffer.

Most buffer functions assume the current buffer if no argument is given. Some requires a argument. The argument can usually be a buffer's name, or a buffer object.

Get Buffer Name

buffer-name
(buffer-name &optional BUFFER)
Return the name of current buffer.
buffer-file-name
(buffer-file-name &optional BUFFER)
Return the full path of the file, or nil if not a file.

Switch Buffer

with-current-buffer
(with-current-buffer BUFFER-OR-NAME &rest BODY)
Temporarily make a buffer current.

Most of the time, you want to use this. Because it takes care of switching back to the original buffer when the function is done.

;; make myBuf current temporarily
(with-current-buffer myBuf
  ;; code to edit text here
)
set-buffer
(set-buffer BUFFER-OR-NAME)
Switch to a given buffer. (but does not make the buffer visible.)
(save-current-buffer

  ;; switch to myBuf
  (set-buffer myBuf)

  ;; do stuff, such as insert/delete text
  )

Note, there is also switch-to-buffer, but it's not designed to be used in lisp code. Use it only if you need the buffer to be visible.

Create Buffer

with-temp-buffer
(with-temp-buffer &rest BODY)
Create a temporary buffer, and evaluate BODY there like progn.
;; use a temp buffer to manipulate string

(setq myStr "big text")

(with-temp-buffer
  (insert myStr)

  ;; manipulate the string here

  ;; print whole buffer content
  (message "%s" (buffer-string)))

Note: most of the time, you should just use with-temp-buffer to create new buffers. Because that saves you code of creating buffer, switching to it, do something, possibly close it, and restore (switch back) to the buffer that was current.

generate-new-buffer
(generate-new-buffer NAME)
Create and return a buffer with a name based on NAME. Buffer name is created by calling generate-new-buffer-name.

Typically used like this:

;; name for new buffer. If start with space, undo is disabled
(setq newBufName " xyz")

;; create a new buffer, save it to a var, so later you can switch to it or kill it
(setq newBuf (generate-new-buffer newBufName))

;; make it current (but does not make it visible), so all insert etc operations works on it.
(set-buffer newBuf)
get-buffer-create
(get-buffer-create BUFFER-OR-NAME)
• Returns the buffer, but doesn't make it current. use set-buffer to make it current.
BUFFER-OR-NAME can be a string or buffer.
If BUFFER-OR-NAME is a buffer datatype and the buffer exists, it's just returned. if not exist, new is created.
If BUFFER-OR-NAME is a string and start with a space, undo is not enabled.
;; create new buffer, without undo info. make sure the string passed is unique and has space in front
(setq newBuf (get-buffer-create " xyz"))

;; make it current (but does not make it visible), so all insert etc operations works on it.
(set-buffer newBuf)

Kill Buffer

kill-buffer
(kill-buffer &optional BUFFER-OR-NAME)
Close current buffer or a specified buffer.

(info "(elisp) Buffers")

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