renumber-offset

gistfile1.el

(defun renumber-offset (&optional offset regex subexp)
  "Add OFFSET to any number matching REGEXP.
If OFFSET is nil then 1 is chosen.
If REGEXP is nil then only numbers at the beginning of line are replaced.
SUBEXP can be used to give the number of the subexp of REGEX."
  (interactive "p")
  (setq offset (or offset 1))
  (setq regex (or regex "^[[:digit:]]+"))
  (save-excursion
    (goto-char (point-min))
    (while (re-search-forward "^[[:digit:]]+" nil t)
           (replace-match (number-to-string
                           (+ offset (string-to-number
                                      (match-string-no-properties (or subexp 0)))))
                          nil t nil subexp))))