Emacs Lisp: Make Backup of Current File

By Xah Lee. Date: . Last updated: .

Here's a simple command to backup the current file.

(defun xah-make-backup ()
  "Make a backup copy of current file or dired marked files.
If in dired, backup current file or marked files.
The backup file name is
 ‹name›~‹timestamp›~
example:
 file.html~20150721T014457~
in the same dir. If such a file already exist, it's overwritten.
If the current buffer is not associated with a file, nothing's done.
URL `http://ergoemacs.org/emacs/elisp_make-backup.html'
Version 2015-10-14"
  (interactive)
  (let ((ξfname (buffer-file-name)))
    (if ξfname
        (let ((ξbackup-name
               (concat ξfname "~" (format-time-string "%Y%m%dT%H%M%S") "~")))
          (copy-file ξfname ξbackup-name t)
          (message (concat "Backup saved at: " ξbackup-name)))
      (if (string-equal major-mode "dired-mode")
          (progn
            (mapc (lambda (ξx)
                    (let ((ξbackup-name
                           (concat ξx "~" (format-time-string "%Y%m%dT%H%M%S") "~")))
                      (copy-file ξx ξbackup-name t)))
                  (dired-get-marked-files))
            (message "marked files backed up"))
        (user-error "buffer not file nor dired")))))
(defun xah-make-backup-and-save ()
  "backup of current file and save, or backup dired marked files.
For detail, see `xah-make-backup'.
If the current buffer is not associated with a file, nothing's done.
URL `http://ergoemacs.org/emacs/elisp_make-backup.html'
Version 2015-10-14"
  (interactive)
  (if (buffer-file-name)
      (progn
        (xah-make-backup)
        (when (buffer-modified-p)
          (save-buffer)))
    (progn
      (xah-make-backup))))

You can give one of the command a key, such as 【F8】. 〔➤see Emacs: How to Define Keys

To delete all backups of current directory, in dired, press【~ x】(that's dired-flag-backup-filesdired-do-flagged-delete) 〔➤see Emacs: File Management (dired tutorial)

To jump from current file to its dired location, call dired-jump.

〔➤see Emacs: Turn Off Auto Backup; Set Backups into a Directory; How to Delete Backup Files

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