(parent-dir "/home/sk/parent/ab.el")
gives
"/home/sk/parent"
then,
(parent-dir "/home/sk/parent")
gives
"/home/sk"
Any elisp function as parent-dir
that gives basepath for both file path & dir path?
file-name-directory
does what you request.
However, (file-name-directory "/home/sk/parent/")
(with a trailing slash) returns that same directory, not its parent.
This does what I'm guessing you really want:
(file-name-directory (directory-file-name "/home/sk/parent/ab.el")) ; => "/home/sk/parent/"
(file-name-directory (directory-file-name "/home/sk/parent/")) ; => "/home/sk/"
(file-name-directory (directory-file-name "/home/sk/parent")) ; => "/home/sk/"
And library Dired+ uses this function:
(defun diredp-parent-dir (file &optional relativep)
"Return the parent directory of FILE, or nil if none.
Optional arg RELATIVEP non-nil means return a relative name, that is,
just the parent component."
(let ((parent (file-name-directory (directory-file-name (expand-file-name file))))
relparent)
(when relativep
(setq relparent (file-name-nondirectory (directory-file-name parent))))
(and (not (equal parent file)) (or relparent parent))))
(defun parent-directory (dir)
(unless (equal "/" dir)
(file-name-directory (directory-file-name dir))))
Taken from https://stackoverflow.com/a/14096693/5103881