code to grab all the strings matching a given regex and put them in a buffer, along with sample use for IPs

collect-ips.el

(defun collect-regexp-results (regex)
  ;;; collects all the matches of regex in a buffer called *collect-result*
  ;;; then switches to that buffer
  ;;; TODO refactor this to take the region as a parameter
  (interactive "Mregex to search for: ")
  (let ((curmin (region-or-buffer-beginning))
        (curmax (region-or-buffer-end)))
    (save-excursion
      (goto-char curmin)
      ;; (goto-char (region-or-buffer-beginning))
      (while (re-search-forward regex curmax t)
        (let ((retval (match-string-no-properties 0)))
          (with-current-buffer (get-buffer-create "*collect results*")
            (insert retval)
            (insert "\n"))))
      (switch-to-buffer "*collect results*"))))

(defun collect-ip-addresses ()
  (interactive)
  (collect-regexp-results "[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+"))