Emacs lisp: How can I get the newest file in a directory?

Question

Given the path of a directory, how can I return the path of the newest file in that directory?

Answer 1

Using f:

(defun aj-fetch-latest (path)
  (let ((e (f-entries path)))
    (car (sort e (lambda (a b)
                   (not (time-less-p (aj-mtime a)
                                     (aj-mtime b))))))))
(defun aj-mtime (f) (let ((attrs (file-attributes f))) (nth 5 attrs)))

Answer 2

Using built-in APIs can achieve as well:

(defun latest-file (path)
  "Get latest file (including directory) in PATH."
  (car (directory-files path 'full nil #'file-newer-than-file-p)))

(latest-file "~/.emacs.d") ;; => "/Users/xcy/.emacs.d/var"

If you also needs files under sub-directory, use directory-files-recursively rather than directory-files. If you want to exclude directories, filter the file/directory list first by using file-directory-p.

Answer 3

If you want to do it without dependencies

• directory-files-and-attributes gives us a list of files and directories with attributes
  • the 4th arg NOSORT is a bool and does not take a function as the top answer suggests

  (directory-files-and-attributes DIRECTORY &optional FULL MATCH NOSORT ID-FORMAT)
  If NOSORT is non-nil, the list is not sorted--its order is unpredictable. NOSORT is useful if you plan to sort the result yourself.

  • attributes are in the format of file-attributes - which gives us the modification time and whether the item is a file or directory

  0. t for directory, string (name linked to) for symbolic link, or nil.\
  1. Last modification time, likewise. This is the time of the last

(car
 (seq-find
  '(lambda (x) (not (nth 1 x))) ; non-directory
  (sort
   (directory-files-and-attributes path 'full nil t)
   '(lambda (x y) (time-less-p (nth 5 y) (nth 5 x)))))) ; last modified first: y < x