init.el

(defun search-all-buffers (regexp prefix)
  "Searches file-visiting buffers for occurence of REGEXP.  With
prefix > 1 (i.e., if you type C-u \\[search-all-buffers]),
searches all non-hidden buffers; with C-u C-u, searches *all*
buffers."
  (interactive (list (grep-read-regexp)
                     current-prefix-arg))
  (multi-occur
   (if (member prefix '(4 (4)))
       (buffer-list)
     (remove-if
      (lambda (b) (some (lambda (rx) (string-match rx  (file-name-nondirectory (buffer-file-name b)))) search-all-buffers-ignored-files))
      (remove-if-not 'buffer-file-name (buffer-list))))

   regexp))

(global-set-key (kbd "<f7>") 'search-all-buffers)