Subject: bug#22828: 25.1.50; Mark symlinks whose target matches regexp

From: Tino Calancha <[email-masked]>
Date: Sun, 28 Feb 2016 19:38:19 +0900 (JST)

> Use dired-move-to-end-of-filename to find the proper place.
I see, this way we forget about the '@ -> ' or ' -> ' 
(or any other?).

Do you think is ok that fn contains such ' -> ' thing?
I would prefer if fn doesn't contain that.
So, the question is:
do we have a portable way to get the target of one link?
We may introduce something like:
dired-symlink-target (if doesn't exist)
diff --git a/lisp/dired.el b/lisp/dired.el
index 6c7445c..6e70cd9 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -1493,6 +1493,7 @@ dired-mode-map
     (define-key map "%d" 'dired-flag-files-regexp)
     (define-key map "%g" 'dired-mark-files-containing-regexp)
     (define-key map "%m" 'dired-mark-files-regexp)
+    (define-key map "%@" 'dired-mark-symlinks-regexp)
     (define-key map "%r" 'dired-do-rename-regexp)
     (define-key map "%C" 'dired-do-copy-regexp)
     (define-key map "%H" 'dired-do-hardlink-regexp)
@@ -1730,6 +1731,9 @@ dired-mode-map
     (define-key map [menu-bar regexp flag]
       '(menu-item "Flag..." dired-flag-files-regexp
 		  :help "Flag files matching regexp for deletion"))
+    (define-key map [menu-bar regexp mark-sym]
+      '(menu-item "Mark Symlinks Target..." dired-mark-symlinks-regexp
+		  :help "Mark symbolic links whose target matches regexp for future operations"))
     (define-key map [menu-bar regexp mark]
       '(menu-item "Mark..." dired-mark-files-regexp
 		  :help "Mark files matching regexp for future operations"))
@@ -3345,6 +3349,31 @@ dired-mark-files-regexp
 	    (and fn (string-match-p regexp fn))))
      "matching file")))
 
+(defun dired-mark-symlinks-regexp (regexp &optional marker-char)
+  "Mark all symbolic links whose target file matches REGEXP
+for use in later commands.
+A prefix argument means to unmark them instead.
+
+REGEXP is an Emacs regexp, not a shell wildcard.  Thus, use ‘\.o$’ for
+object files--just ‘.o’ will mark more than you might think."
+  (interactive
+   (list (read-regexp (concat (if current-prefix-arg "Unmark" "Mark")
+                              " symlinks target (regexp): ")
+                      nil 'dired-regexp-history)
+         (if current-prefix-arg ?\040)))
+  (let ((dired-marker-char (or marker-char dired-marker-char)))
+    (dired-mark-if
+     (and (looking-at-p dired-re-sym)
+          (not (looking-at-p dired-re-dot))
+          (not (eolp))			; empty line
+          
+          (let* ((eol (line-end-position))
+                 (fn (save-excursion
+                       (and (dired-move-to-end-of-filename 'noerror)
+                            (buffer-substring-no-properties (point) eol)))))
+            (and fn (string-match-p regexp fn))))
+     "matching symbolic link")))
+
 (defun dired-mark-files-containing-regexp (regexp &optional marker-char)
   "Mark all files with contents containing REGEXP for use in later commands.
 A prefix argument means to unmark them instead.