Finding the size of directory with multiply hardlinked files

[Roberto Ragusa]

Dean S. Messing wrote:
> Thanks Roberto.  That's _exactly_ what I want.
> 
> I saw the -c option of `du' in the man page when
> trying to figure this out but it just says
> 
>        -c, --total
>               produce a grand total
> 
> Pray tell, how did you figure this out.
> I've re-read the man page and I don't see this
> this differential behaviour advertised anywhere.

I just got it by testing and observing results.

Actually, the "-c" is not needed at all, it's there
because I also want to know the total space used by backups.

And... the "-s" is also not needed! It just avoids the
printing of all the subtotals of the subdirectories of
your backups.

It looks like du simply discard everything already
found on its way when calculating disk space.

Look at this:

$ mkdir d
$ head -c 1000000 /dev/zero >f1
$ ln d/f1 d/f2
$ cp d/f1 d/f3

Now, this command reports only two files and not the third (hardlinked):

$ du d
1962    d

And, look at this; f2 is totally ignored even if it appears on the
command line:

$ du d/f1 d/f2 d/f3
981     d/f1
981     d/f3

Amazing.

-- 
    Roberto Ragusa    mail at robertoragusa.it