Emacs copy matching lines

Question

In Emacs how can I easily copy all lines matching a particular regex? Preferably highlighting the matching lines as I type.

occur gets partway there by

Answer 1

I've been using this happily for a long time:

    (defun occur-mode-clean-buffer ()
  "Removes all commentary from the *Occur* buffer, leaving the
unadorned lines."
  (interactive)
  (if (get-buffer "*Occur*")
      (save-excursion
        (set-buffer (get-buffer "*Occur*"))
        (fundamental-mode)
        (goto-char (point-min))
        (toggle-read-only 0)
        (set-text-properties (point-min) (point-max) nil)
        (if (looking-at (rx bol (one-or-more digit)
                            (or " lines matching \""
                                " matches for \"")))
            (kill-line 1))
        (while (re-search-forward (rx bol
                                      (zero-or-more blank)
                                      (one-or-more digit)
                                      ":")
                                  (point-max)
                                  t)
          (replace-match "")
          (forward-line 1)))

    (message "There is no buffer named \"*Occur*\".")))

(define-key occur-mode-map (kbd "C-c C-x") 'occur-mode-clean-buffer)