Steal `multi-occur-in-this-mode' from Mastering Emacs

README.org

@@ -1580,6 +1580,32 @@ the current [[https://en.wikipedia.org/wiki/Version_control][VCS]] directory tre
     (keymap-set deadgrep-mode-map "C-c C-w" #'deadgrep-edit-mode)))
 #+end_src
 
+** [[https://www.masteringemacs.org/article/searching-buffers-occur-mode][Searching and Editing in Buffers with Occur Mode]]
+:PROPERTIES:
+:CUSTOM_ID: sec:occur
+:END:
+
+#+caption[Define =multi-occur-in-this-mode=]:
+#+caption: Define =multi-occur-in-this-mode=.
+#+name: lst:multi-occur-in-this-mode
+#+begin_src emacs-lisp -n :results silent
+(defun get-buffers-matching-mode (mode)
+  "Return a list of buffers whose major-mode is equal to MODE."
+  (let ((buffer-mode-matches '()))
+    (dolist (buf (buffer-list))
+      (with-current-buffer buf
+        (when (eq mode major-mode)
+          (push buf buffer-mode-matches))))
+    buffer-mode-matches))
+
+(defun multi-occur-in-this-mode ()
+  "Show all lines matching REGEXP in buffers with this major mode."
+  (interactive)
+  (multi-occur
+   (get-buffers-matching-mode major-mode)
+   (car (occur-read-primary-args))))
+#+end_src
+
 ** [[https://www.genivia.com/get-ugrep.html][Ugrep]]
 :PROPERTIES:
 :CUSTOM_ID: sec:ugrep