Finding the size of directory with multiply hardlinked files

[Patrick O'Callaghan]

On Thu, 2008-03-13 at 19:48 -0700, Dean S. Messing wrote:
> I have a sequence of directories that have many multiply
> (cross)hardlinked files, and I'd like to see what their
> "true" sizes are.  These dirs are backup directories
> created with something like:
> 
> rsync -a --delete --link-dest=/mnt/bkup/backup_A/ \
>       /dir_to_back_up /mnt/bkup/backup_B/
> 
> By "true" sizes I mean this:
> 
> Say backup_A was created first.  If I do `du_true
> backup_A' I shd. see its size.  Now I delete some files
> in "/dir_to_back_up" and create some other new files.
> Now I create "backup_B" with the above rsync command.  I'd
> like for my mythical `du_true' to compute the
> incremental change in size from backup_A to backup_B.
> 
> This seems like a non-trivial problem but maybe I'm just
> missing something simple.

What's wrong with "subtract 'du -s backup_B' from 'du -s backup_A'"?

If this isn't what you mean, then you need to explain it better. The
concept of files being "in" a directory is just a convenient fiction.
Both backup_A and backup_B are just sets of hard links.

poc