Emacs: Upcase Sentences 📜

Here's emacs command to fix letter case of sentences. That is, any letter after a period (full stop), question mark, exclamation, will be capitalized.

This saves you typing. You can keep typing without pressing Shift to type uppercase letters. After you finished typing a paragraph, you can press a button and have the letters capitalized.

put this in your Emacs Init File:

(defun xah-upcase-sentence ()
  "Upcase first letters of sentences of current block or selection.

URL `http://xahlee.info/emacs/emacs/emacs_upcase_sentence.html'
Created: 2020-12-08
Version: 2025-03-25"
  (interactive)
  (let (xbeg xend)
    (seq-setq (xbeg xend) (if (region-active-p) (list (region-beginning) (region-end)) (list (save-excursion (if (re-search-backward "\n[ \t]*\n" nil 1) (match-end 0) (point))) (save-excursion (if (re-search-forward "\n[ \t]*\n" nil 1) (match-beginning 0) (point))))))
    (save-restriction
      (narrow-to-region xbeg xend)
      (let ((case-fold-search nil))
        ;; after period or question mark or exclamation
        (goto-char (point-min))
        (while (re-search-forward "\\(\\.\\|\\?\\|!\\)[ \n]+ *\\([a-z]\\)" nil 1)
          (upcase-region (match-beginning 2) (match-end 2))
          (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))
        ;; after a blank line, after a bullet, or beginning of buffer
        (goto-char (point-min))
        (while (re-search-forward "\\(\\`\\|• \\|\n\n\\)\\([a-z]\\)" nil 1)
          (upcase-region (match-beginning 2) (match-end 2))
          (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))
        ;; for HTML. first letter after tag
        (when
            (or
             (eq major-mode 'xah-html-mode)
             (eq major-mode 'html-mode)
             (eq major-mode 'sgml-mode)
             (eq major-mode 'nxml-mode)
             (eq major-mode 'xml-mode)
             (eq major-mode 'mhtml-mode))
          (goto-char (point-min))
          (while
              (re-search-forward "\\(<title>[ \n]?\\|<h[1-6]>[ \n]?\\|<p>[ \n]?\\|<li>[ \n]?\\|<dd>[ \n]?\\|<td>[ \n]?\\|<br ?/?>[ \n]?\\|<figcaption>[ \n]?\\)\\([a-z]\\)" nil 1)
            (upcase-region (match-beginning 2) (match-end 2))
            (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))))
      (goto-char (point-max)))
    (skip-chars-forward " \n\t")))