Re: [Findutils-patches] [PATCH] -delete requires -depth

[Bruno De Fraine]

On 23 Aug 2007, at 14:59, Eric Blake wrote:
> Bruno also had the idea of letting -delete operate
> without -depth, by letting -delete swap the traversal of that  
> subtree to
> depth-first while the rest of the traversal is breadth-first prior to
> encountering the -delete action.

Actually, not quite. My proposal amounted to exactly the following:

--- findutils-4.3.8/find/parser.c       2007-06-09 14:12:06.000000000  
+0200
+++ findutils-mod/find/parser.c 2007-08-24 12:08:07.000000000 +0200
@@ -724,7 +724,7 @@
   our_pred = insert_primary (entry);
   our_pred->side_effects = our_pred->no_default_print = true;
-  /* -delete implies -depth */
-  options.do_dir_first = false;

   /* We do not need stat information because we check for the case
    * (errno==EISDIR) in pred_delete.

The idea is to have a very straightforward -delete: the action will  
try to delete the nodes in order, the traversal is not modified in  
any way. The main benefit over other proposals is that -delete can be  
combined with normal traversal (and thus with pruning). For example,  
consider:

$ ../findutils-mod/find/find
.
./aa
./aa/.svn
./aa/.svn/foo
./aa/foo
./bb
./bb/foo
./.svn
./.svn/foo
$ ../findutils-mod/find/find -not "(" -name .svn -prune ")" -name foo  
-delete
$ ../findutils-mod/find/find
.
./aa
./aa/.svn
./aa/.svn/foo
./bb
./.svn
./.svn/foo

The user will have to make sure that nodes can actually be deleted  
during the traversal, otherwise he will receive an error. When  
deleting directories, this means that the directory must be empty. If  
he wants to delete an entire directory tree as a part of one and the  
same traversal, he will need to use -depth, but at least he will  
knowingly change the traversal order then.

Also, after deleting a directory in a normal traversal, find should  
not try to visit this directory anymore, because it's gone. The user  
could accomplish this by including a -prune after the -delete, or  
find could do it automatically, with a change like this:

--- findutils-4.3.8/find/pred.c 2007-06-09 14:12:35.000000000 +0200
+++ findutils-mod/find/pred.c   2007-08-26 19:30:45.000000000 +0200
@@ -392,6 +392,8 @@
        flags |= AT_REMOVEDIR;
       if (perform_delete(flags))
        {
+         if (options.do_dir_first == true && (flags & AT_REMOVEDIR))
+         state.stop_at_current_level = true;
          return true;
        }
       else
@@ -403,7 +405,11 @@
                  /* unlink() operation failed because we should  
have done rmdir(). */
                  flags |= AT_REMOVEDIR;
                  if (perform_delete(flags))
+                 {
+                   if (options.do_dir_first == true && (flags &  
AT_REMOVEDIR))
+                   state.stop_at_current_level = true;
                    return true;
+                 }
                }
            }
        }

As such it is possible to -delete empty directories in a normal  
traversal. For example, consider the following to clean empty  
subdirectories in a tree:

$ ../findutils-mod/find/find
.
./aa
./aa/foo
./bb
./cc
$ ../findutils-mod/find/find -type d
.
./aa
./aa/foo
./cc
$ ../findutils-mod/find/find -type d -empty -delete
$ ../findutils-mod/find/find
.
./aa
./bb


Regards,
Bruno De Fraine