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 coping them into a buffer, but it adds lots of extra stuff.

Answer 1

How about this:

(defun copy-lines-matching-re (re)
  "find all lines matching the regexp RE in the current buffer
putting the matching lines in a buffer named *matching*"
  (interactive "sRegexp to match: ")
  (let ((result-buffer (get-buffer-create "*matching*")))
    (with-current-buffer result-buffer 
      (erase-buffer))
    (save-match-data 
      (save-excursion
        (goto-char (point-min))
        (while (re-search-forward re nil t)
          (princ (buffer-substring-no-properties (line-beginning-position) 
                                                 (line-beginning-position 2))
                 result-buffer))))
    (pop-to-buffer result-buffer)))