How can I recursively delete all empty directories?

Question

That is, if I have

-empty-dir-a/
-nonempty-dir-a/
  -empty-dir-a/
    -empty-dir-a/
  file-a
file-a
file-b

I would like

-nonempty-dir-a/
  file-a
file-a
file-b

---

I'm aware that there are many OS-specific solutions to this, but I'd like to stick to elisp, ideally :).

Answer 1

You could just use the find tool.

M-! find . -empty -type d -delete return

Here it is wrapped in a function that confirms the delete:

(defun delete-empty-dirs ()
  (interactive)
  (let ((dirs (split-string (shell-command-to-string "find -X $(pwd) -empty -type d") "[ \n]" t)))
    (when (yes-or-no-p (format "Delete %d empty directories? " (length dirs)))
      (with-temp-buffer (shell-command "find -X $(pwd) -empty -type d -delete")))))

Answer 2

This requires the following functions from f.el, available from MELPA:

• f-directories returns a list of directories in the given directory
• f-entries returns all files and folders in the given directory

(defun *-delete-empty-directories (root-directory)
  "Recursively delete empty directories in ROOT-DIRECTORY.

When called from dired, `dired-current-directory' is used for
ROOT-DIRECTORY."

  ;; Interface
  (interactive (list (if (eq major-mode 'dired-mode)
                         (expand-file-name (dired-current-directory))
                       (read-from-minibuffer "Root directory: "))))
  (when (or (null root-directory) (string= "" root-directory))
    (user-error "No root directory provided"))
  (when (called-interactively-p 'interactive)
    (unless (yes-or-no-p (format "Delete all non-empty directories in `%s'? "
                                 root-directory))
      (user-error "Directory `%s' has been left untouched" root-directory)))

  ;; Implementation
  (require 'f)
  (let ((entries (f-directories root-directory)))
    (while entries
      (let ((curdir (car entries)))
        (when (f-directories curdir)
          (*-delete-empty-directories curdir))
        (unless (f-entries curdir)
          (delete-directory curdir)
          (message "Directory deleted: `%s'" curdir))
        (setq entries (cdr entries))))))