Elisp: Case Sensitivity (case-fold-search)

case-fold-search

Case sensitivity for search is controlled by the variable case-fold-search

case-fold-search

Variable. Control case-sensitivity for functions that do text search, including commands that take a Emacs Regular Expression.

• Value of t means smart. That is, if search term contain Capital letters, the search is case-sensitive, otherwise no.
• nil means search is case-sensitive.
• By default, the value is t.

Example of case-fold-search true:

• dragon matches {dragon, Dragon, DRAGON, draGON}
• Dragon matches only Dragon.

the following functions are effected:

• search-forward
• re-search-forward
• string-match
• replace-regexp-in-string

• not skip-chars-forward

Change Case Sensitivity in Emacs Lisp Code

In elisp code, set case-fold-search like this:

(let ((case-fold-search nil))

  (re-search-forward "ABC")

  ;; other code here
  )

Case Sensitivity in Replacement, Text Replace Functions

replace-match function has a option for it.