File path to clipboard in Emacs

I use this:

(defun my-put-file-name-on-clipboard ()
  "Put the current file name on the clipboard"
  (interactive)
  (let ((filename (if (equal major-mode 'dired-mode)
                      default-directory
                    (buffer-file-name))))
    (when filename
      (with-temp-buffer
        (insert filename)
        (clipboard-kill-region (point-min) (point-max)))
      (message filename))))

Why no one tell the simple solution.

Just go to your dired buffer then press 0 w or C-u 0 w.

This will call dired-copy-filename-as-kill which gives you full path of a file. If you want current dir, just delete the file at the end of it or you can use the function below, then bind it to any key you like.

(defun my/dired-copy-dirname-as-kill ()
  "Copy the current directory into the kill ring."
  (interactive)
  (kill-new default-directory))

PS: personally I go to current directory from file buffer using dired-jump