I've made the following command:

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

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


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?

  • 1
    case-fold-search should be nil.
    – abo-abo
    Jan 18, 2016 at 9:17
  • @abo-abo Thanks! Now it works. It seems it doesn't affect the helm or isearch. Is it only for regexp?
    – stacko
    Jan 18, 2016 at 9:23
  • It's for regexp, but isearch and helm might bind case-fold-search at some points.
    – abo-abo
    Jan 18, 2016 at 9:32
  • @abo-abo Would it be a bad idea to start my function by setting case-fold-search nil and end it with setting it 1, if I ever made sure that it actually affects isearch and helm?
    – stacko
    Jan 18, 2016 at 9:44
  • @abo-abo I might delete this comment since it's kind of off-topic, but why is that you don't post this as an answer? I could upvote and choose "this solved my question"?
    – stacko
    Jan 18, 2016 at 9:47

2 Answers 2


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 ()
  (let ((case-fold-search nil))
    (search-backward-regexp "[a-z]")))

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).

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