+(defun dired-compare-directories (dir2 predicate)
+ "Mark files with different file attributes in two dired buffers.
+Compare file attributes of files in the current directory
+with file attributes in directory DIR2 using PREDICATE on pairs of files
+with the same name. Mark files for which PREDICATE returns non-nil.
+Mark files with different names if PREDICATE is nil (or interactively
+when the user enters empty input at the predicate prompt).
+
+PREDICATE is a Lisp expression that can refer to the following variables:
+
+ size1, size2 - file size in bytes
+ mtime1, mtime2 - last modification time in seconds, as a float
+ fa1, fa2 - list of file attributes
+ returned by function `file-attributes'
+
+ where 1 refers to attribute of file in the current dired buffer
+ and 2 to attribute of file in second dired buffer.
+
+Examples of PREDICATE:
+
+ (> mtime1 mtime2) - mark newer files
+ (not (= size1 size2)) - mark files with different sizes
+ (not (string= (nth 8 fa1) (nth 8 fa2))) - mark files with different modes
+ (not (and (= (nth 2 fa1) (nth 2 fa2)) - mark files with different UID
+ (= (nth 3 fa1) (nth 3 fa2)))) and GID."
+ (interactive
+ (list (read-file-name (format "Compare %s with: "
+ (dired-current-directory))
+ (dired-dwim-target-directory))
+ (read-from-minibuffer "Mark if (lisp expr or RET): " nil nil t nil "nil")))
+ (let* ((dir1 (dired-current-directory))
+ (file-alist1 (dired-files-attributes dir1))
+ (file-alist2 (dired-files-attributes dir2))
+ (file-list1 (mapcar
+ 'cadr
+ (dired-file-set-difference
+ file-alist1 file-alist2
+ predicate)))
+ (file-list2 (mapcar
+ 'cadr
+ (dired-file-set-difference
+ file-alist2 file-alist1
+ predicate))))
+ (dired-fun-in-all-buffers
+ dir1 nil
+ (lambda ()
+ (dired-mark-if
+ (member (dired-get-filename nil t) file-list1) nil)))
+ (dired-fun-in-all-buffers
+ dir2 nil
+ (lambda ()
+ (dired-mark-if
+ (member (dired-get-filename nil t) file-list2) nil)))
+ (message "Marked in dir1: %s files, in dir2: %s files"
+ (length file-list1)
+ (length file-list2))))
+
+(defun dired-file-set-difference (list1 list2 predicate)
+ "Combine LIST1 and LIST2 using a set-difference operation.
+The result list contains all file items that appear in LIST1 but not LIST2.
+This is a non-destructive function; it makes a copy of the data if necessary
+to avoid corrupting the original LIST1 and LIST2.
+PREDICATE (see `dired-compare-directories') is an additional match
+condition. Two file items are considered to match if they are equal
+*and* PREDICATE evaluates to t."
+ (if (or (null list1) (null list2))
+ list1
+ (let (res)
+ (dolist (file1 list1)
+ (unless (let ((list list2))
+ (while (and list
+ (not (let* ((file2 (car list))
+ (fa1 (caddr file1))
+ (fa2 (caddr file2))
+ (size1 (nth 7 fa1))
+ (size2 (nth 7 fa2))
+ (mtime1 (float-time (nth 5 fa1)))
+ (mtime2 (float-time (nth 5 fa2))))
+ (and
+ (equal (car file1) (car file2))
+ (not (eval predicate))))))
+ (setq list (cdr list)))
+ list)
+ (setq res (cons file1 res))))
+ (nreverse res))))
+
+(defun dired-files-attributes (dir)
+ "Return a list of all file names and attributes from DIR.
+List has a form of (file-name full-file-name (attribute-list))"
+ (mapcar
+ (lambda (file-name)
+ (let ((full-file-name (expand-file-name file-name dir)))
+ (list file-name
+ full-file-name
+ (file-attributes full-file-name))))
+ (directory-files dir)))
+\f