Add new function 'file-name-split'

* doc/lispref/files.texi (File Name Components): Document it.
* lisp/files.el (file-name-split): New function (bug#50572).

* lisp/emacs-lisp/shortdoc.el (file-name): Mention it.

2 files changed, 26 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/shortdoc.el b/lisp/emacs-lisp/shortdoc.el
index c3d6c742940..a9f548b104e 100644
--- a/lisp/emacs-lisp/shortdoc.el
+++ b/lisp/emacs-lisp/shortdoc.el
@@ -281,6 +281,9 @@ There can be any number of :example/:result elements."
    :eval (file-name-base "/tmp/foo.txt"))
   (file-relative-name
    :eval (file-relative-name "/tmp/foo" "/tmp"))
+  (file-name-split
+   :eval (file-name-split "/tmp/foo")
+   :eval (file-name-split "foo/bar"))
   (make-temp-name
    :eval (make-temp-name "/tmp/foo-"))
   (file-name-concat
diff --git a/lisp/files.el b/lisp/files.el
index 0bc7a92fbea..c694df38268 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -5051,6 +5051,29 @@ See also `file-name-sans-extension'."
   (file-name-sans-extension
    (file-name-nondirectory (or filename (buffer-file-name)))))
 
+(defun file-name-split (filename)
+  "Return a list of all the components of FILENAME.
+On most systems, this will be true:
+
+  (equal (string-join (file-name-split filename) \"/\") filename)"
+  (let ((components nil))
+    ;; If this is a directory file name, then we have a null file name
+    ;; at the end.
+    (when (directory-name-p filename)
+      (push "" components)
+      (setq filename (directory-file-name filename)))
+    ;; Loop, chopping off components.
+    (while (length> filename 0)
+      (push (file-name-nondirectory filename) components)
+      (let ((dir (file-name-directory filename)))
+        (setq filename (and dir (directory-file-name dir)))
+        ;; If there's nothing left to peel off, we're at the root and
+        ;; we can stop.
+        (when (equal dir filename)
+          (push "" components)
+          (setq filename nil))))
+    components))
+
 (defcustom make-backup-file-name-function
   #'make-backup-file-name--default-function
   "A function that `make-backup-file-name' uses to create backup file names.