Regexp for distinguishing uppercase and lowercase not working

Question

I've made the following command:

(defun search-backward-lowercase-alphabet ()
  (interactive)
  (search-backward-regexp "[a-z]"))

But when I run it at the end of a line like the following:

abcDEF

It just selects the last letter F, when I actually want to select the c. It doesn't distinguish between uppercase and lowercase at all. How can I fix this?

Answer 1

As suggested by @abo-abo, you should set case-fold-search to nil. However, in order to ensure that it doesn't affect any other part of the system, you can bind in using let, as follows:

(defun search-backward-lowercase-alphabet ()
  (interactive)
  (let ((case-fold-search nil))
    (search-backward-regexp "[a-z]")))

Answer 2

Check your setting of case-fold-search:

Documentation: Non-nil if searches and matches should ignore case.

This means you need (setq case-fold-search nil).