Emacs: Backup Current File 💠

Here's a command to backup the current file or marked files in dired.

(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 in this format
 x.html~2018-05-15_133429~
The last part is hour, minutes, seconds.

Overwrite existing file.

If the current buffer is not associated with a file, nothing's done.

URL `http://xahlee.info/emacs/emacs/elisp_make-backup.html'
Version: 2018-06-06 2022-06-13 2024-04-21"
  (interactive)
  (let ((xfname buffer-file-name)
        (xdateTimeFormat "%Y-%m-%d_%H%M%S"))
    (if xfname
        (let ((xbackupName
               (concat xfname "~" (format-time-string xdateTimeFormat) "~")))
          (copy-file xfname xbackupName t)
          (message (concat "\nBackup saved at: " xbackupName)))
      (if (eq major-mode 'dired-mode)
          (progn
            (mapc (lambda (xx)
                    (let ((xbackupName
                           (concat xx "~" (format-time-string xdateTimeFormat) "~")))
                      (copy-file xx xbackupName t)))
                  (dired-get-marked-files))
            (revert-buffer))
        (user-error "%s: buffer not file nor dired" real-this-command)))))

(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 nor dired, nothing's done.
URL `http://xahlee.info/emacs/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))))