Emacs Buffer

Emacs Buffer Skill

Display Guidelines

E-ink Monitor Compatibility: User uses an e-ink monitor that only supports black, white, and grey.

• NEVER use colors (:foreground "red", :foreground "cyan", etc.)
• Use :weight bold, :weight light, :slant italic, :underline t for differentiation
• Standard Emacs faces (font-lock-*-face) are acceptable as they adapt to themes

Buffer Basics

Get current buffer

(current-buffer)      ; returns buffer object
(buffer-name)         ; returns buffer name string
(buffer-file-name)    ; returns file path or nil

Switch to buffer

(switch-to-buffer "buffer-name")
(set-buffer "buffer-name")  ; doesn't change window display
(pop-to-buffer "buffer-name")  ; shows in new window

Create buffer

(get-buffer-create "*my-buffer*")
(with-current-buffer (get-buffer-create "*my-buffer*")
  ;; work in buffer
  )

Kill buffer

(kill-buffer "buffer-name")
(kill-buffer (current-buffer))

Buffer Contents

Read buffer text

(buffer-string)  ; entire buffer
(buffer-substring start end)  ; region
(buffer-substring-no-properties start end)  ; without text properties

Insert text

(insert "text")
(insert-buffer-substring other-buffer start end)

Erase buffer

(erase-buffer)
(delete-region start end)

Buffer Properties

Check buffer state

(buffer-modified-p)  ; unsaved changes?
(buffer-live-p buf)  ; buffer exists?
(get-buffer "name")  ; returns buffer or nil

Set buffer properties

(set-buffer-modified-p nil)  ; mark as saved
(rename-buffer "new-name")

Buffer Lists

List all buffers

(buffer-list)  ; all buffers
(mapcar #'buffer-name (buffer-list))  ; just names

Filter buffers

;; Get file-visiting buffers
(seq-filter #'buffer-file-name (buffer-list))

;; Get buffers matching pattern
(seq-filter (lambda (b)
              (string-match-p "\\*claude" (buffer-name b)))
            (buffer-list))

Working with Buffer Positions

Point operations

(point)          ; current position
(point-min)      ; buffer start
(point-max)      ; buffer end
(goto-char pos)  ; move to position

Save and restore position

(save-excursion
  ;; point and buffer restored after body
  (goto-char (point-min))
  (search-forward "text"))

Temporary Buffers

with-temp-buffer

(with-temp-buffer
  (insert "temporary content")
  (buffer-string))  ; returns content, buffer killed after

Generate new buffer

(generate-new-buffer "*unique-name*")

Buffer-Local Variables

Set buffer-local

(setq-local my-var "value")
(make-local-variable 'my-var)

Check if buffer-local

(local-variable-p 'my-var)
(buffer-local-value 'my-var some-buffer)

Common Patterns

Process buffer safely

(when-let ((buf (get-buffer "*my-buffer*")))
  (with-current-buffer buf
    ;; work with buffer
    ))

Create output buffer

(let ((buf (get-buffer-create "*output*")))
  (with-current-buffer buf
    (erase-buffer)
    (insert "Output:\n")
    (insert result))
  (display-buffer buf))

Find buffer by mode

(seq-find (lambda (b)
            (with-current-buffer b
              (derived-mode-p 'org-mode)))
          (buffer-list))