Subject: Re: bug#7362: dd strangeness

From: Paul Eggert <[email-masked]>
Date: Wed, 10 Nov 2010 10:56:47 -0800

On 11/10/10 08:07, Pádraig Brady wrote:

> BTW here are my notes on some possible changes in this area:
> 
>   `dd conv=sync` seems to do the wrong thing with pipes.
>   I.E. it pads out short reads. Why would one ever want that?

Nobody ever wants it but (as you note) it's required by the
standard.

>   Should sync for pipes imply fullblock?

I think that would be a good idea, but it should be done only
if POSIXLY_CORRECT is not set, since it contradicts the standard.

>   Should sync for pipes without fullblock give a warning?

I would say "no".  If POSIXLY_CORRECT, the warning would arguably
violate the standard.  If not, there's no need for a warning.

>   Should specifying a count (and bs I suppose) without fullblock
>   when reading from pipes give a warning?

No, for the same reason.

Do you have time to implement this change?  If not, I suppose
I could look into it.  It shouldn't be that hard.  The hardest
part would be the documentation.

Regardless of whether we make such a change, we should document
the issue, as this is a common problem.