Re: Emacs Modular Configuration: the preferable way.

[Jean Louis]

* Emanuel Berg via Users list for the GNU Emacs text editor 
<help-gnu-emacs@gnu.org> [2021-06-22 03:04]:
> > In some functions it matters if you end filename with
> > a slash or not when you work with directories.
> 
> I can imagine the situation but if it should do different
> things depending on if it is a directory or a regular file, it
> is better for these functions themselves to determine what it
> is, and not rely on the user of the function to insert a slash
> to denote a directory...

(setq file "") ⇒ ""
(file-exists-p file) ⇒ t ;; this is funny to me, but I guess both
                         ;; directory and file are files...

(file-exists-p "/") ⇒ t  ;; aha, directory is file too...

Then:

(expand-file-name file) ⇒ "/home/data1/protected/tmp" ;; aha, this one is
                                                      ;; directory,
                                                      ;; that is why
                                                      ;; empty string
                                                      ;; is considered
                                                      ;; file.

(file-name-as-directory "") ⇒ "./" ;; now it makes more sense

and now we get it as directory with a slash:

(file-name-as-directory (expand-file-name "")) ⇒ "/home/data1/protected/tmp/"

(defun directory (file)
  (when (and (stringp file) (file-exists-p file))
    (file-name-as-directory (expand-file-name file))))

(directory "") ⇒ "/home/data1/protected/tmp/" ;; because that is my current 
directory

(directory "/home") ⇒ "/home/"

If directory does not exist, return NIL:

(directory "/home-is-not-here") ⇒ nil


-- 
Jean

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