How do I get the region (selection) programmatically in Emacs Lisp?

Question

I need to access the selection in Emacs buffer. I have found this article How do I access the contents of the current region in Emacs Lisp? and it helps me a lot.

But there is a problem. The first time I select (highlight) a region, it works okay, but when I press C-g, and move cursor normally to another place without highlighting any chars, I got a string from last mark to the current point while I expect an empty one.

Actually I need to implement a function which will return the current selection (highlighted) as a string, or empty string if nothing is highlighted. The following code may express me more clearly.

 (defun get-search-term ()   (interactive)   (let (         (selection (buffer-substring-no-properties (region-beginning) (region-end))))     (if (= (length selection) 0)         (message "empty string")       (message selection))))  

Any suggestions? Thanks a lot!

Answer 1

"r" specification of interactive is dumb. You're seeing why.

(defun get-search-term (beg end)   "message region or \"empty string\" if none highlighted"   (interactive (if (use-region-p)                    (list (region-beginning) (region-end))                  (list (point-min) (point-min))))   (let ((selection (buffer-substring-no-properties beg end)))     (if (= (length selection) 0)         (message "empty string")       (message selection)))) 

I don't mean "dumb" as in stupid and not useful; just that it doesn't care about whether the mark is active or not. I think it predates transient-mark-mode.

EDIT: Using (point-min) twice above makes the code harder to understand when re-reading. Here is a better implementation:

(defun get-search-term (beg end)   "message region or \"empty string\" if none highlighted"   (interactive (if (use-region-p)                    (list (region-beginning) (region-end))                  (list nil nil)))   (message "%s" (if (and beg end)                     (buffer-substring-no-properties beg end)                   "empty string")))