Re: dd new iflag= oflag= flags directory, nolinks

[Phillip Susi]

What is atomic about having dd do this?  open() with O_DIRECTORY to test 
for existence of a directory is exactly what test does isn't it?  If 
your goal is to test for the existence of a directory then test is what 
you want to use, not dd.  The purpose of dd is to copy/convert data 
between devices, not test if files or directories exist, so I don't 
think this patch is very appropriate. 

Paul Eggert wrote:
> You can open a directory without writing to it.  Something like this:
>
>    $ mkdir foo
>    $ dd if=foo iflag=directory count=0
>    0+0 records in
>    0+0 records out
>    0 bytes (0 B) copied, 2e-05 seconds, 0 B/s
>
> You can think of this as a way to do a "test -d foo && test -r foo"
> atomically, without race conditions.  Admittedly this is somewhat
> twisted, but the new documentation does say that iflag=directory is of
> "limited utility"....
>
>