Emacs: Upcase Sentences

By Xah Lee. Date: . Last updated: .

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.

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

URL `http://xahlee.info/emacs/emacs/emacs_upcase_sentence.html'
Version 2020-12-08"
  (interactive)
  (let ($p1 $p2)
    (if (use-region-p)
        (setq $p1 (region-beginning) $p2 (region-end))
      (save-excursion
        (if (re-search-backward "\n[ \t]*\n" nil "move")
            (progn
              (setq $p1 (point))
              (re-search-forward "\n[ \t]*\n"))
          (setq $p1 (point)))
        (progn
          (re-search-forward "\n[ \t]*\n" nil "move")
          (setq $p2 (point)))))
    (save-excursion
      (save-restriction
        (narrow-to-region $p1 $p2)
        (let ((case-fold-search nil))
          ;; after period or question mark or exclamation
          (goto-char (point-min))
          (while (re-search-forward "\\(\\.\\|\\?\\|!\\)[ \n]+ *\\([a-z]\\)" nil "move")
            (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 "move")
            (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 "\\(<h[1-6]>[ \n]?\\|<p>[ \n]?\\|<li>\\|<dd>\\|<td>[ \n]?\\|<br ?/?>[ \n]?\\|<figcaption>[ \n]?\\)\\([a-z]\\)" nil "move")
              (upcase-region (match-beginning 2) (match-end 2))
              (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))))))))

The following are often useful together:

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