grep string in recentf-list

recentf-grep.el

(require 'anything-grep)
(defun recentf-grep (str)
  (interactive "sSearch: ")
  (let* ((files (mapconcat #'(lambda (x) (concat "'" x "'"))
                           (filter #'file-readable-p recentf-list) " "))
         (command (concat "grep -i -nH -e " str " " files))
         (pwd "/tmp")
         (src (agrep-source (agrep-preprocess-command command) pwd)))
    (setcdr (assoc 'name src) (format "grep %s in recentf-list" str))
    (anything-grep-base (list src)  (format " *recentf-grep:%s*" str))))