Elisp: Get Script Name at Run Time, Call by Relative Path

Get Current Script's Name Programmatically

;; get the current elisp script's name at run time
(or load-file-name buffer-file-name)

Explanation: If user ran your script by eval-buffer, then load-file-name's value would be nil. So, using both {load-file-name, buffer-file-name } is a good way to get the script name regardless whether the script is executed by load or eval buffer.

If you want the directory, call file-name-directory on the result.

Get Full Path from Relative Path at Run Time

If you have file A, that calls load to load a file at B, and B calls load on file C using a relative path, then Emacs will complain about unable to find C. Because, emacs does not switch current directory with load.

The following function solves this problem.

(defun xah-get-fullpath (RelativePath)
  "Return the full path of RelativePath, relative to caller's file location.
Created: 2017-07-19
Version: 2021-07-17"
  (concat (file-name-directory (or load-file-name buffer-file-name)) RelativePath))

See also: What is the difference between load-file, load, require, autoload?.