GNU bug report logs - #28432
dd: warn about partial read on final iread

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From: Pádraig Brady <P <at> draigBrady.com>
To: Barry Handelman <barry.handelman <at> gmail.com>, 28432 <at> debbugs.gnu.org
Subject: bug#28432: dd doesn't warn about partial read on final call to iread
Date: Wed, 13 Sep 2017 18:11:48 -0700

On 12/09/17 08:51, Barry Handelman wrote:
> The iread function in dd.c issues a warning if the previous read was short,
> suggesting that you use iflag=fullblock
> 
> However, the warning is issued when the previous call to iread was partial,
> so if only the final read was short then no warning is issued.
> Importantly, this will always be the case when there was only one read, and
> it was partial.
> 
> I'd suggest that if the strategy of warning on subsequent reads is to be
> used, the warning routine should be run once again after the final read.

The current approach was discussed at https://bugs.gnu.org/7362
A short read as the last read would be a common situation though?
You're specifically looking for the following to warn?

  (echo; sleep 1; echo) | dd count=1 bs=512

That may be a bit aggressive as that could be used to read
the current data available, up to a specified max.

cheers,
Pádraig.

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