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

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Package: coreutils; Severity: wishlist; Reported by: Barry Handelman <barry.handelman@HIDDEN>; dated Tue, 12 Sep 2017 15:55:02 UTC; Maintainer for coreutils is bug-coreutils@HIDDEN.
Changed bug title to 'dd: warn about partial read on final iread' from 'dd doesn't warn about partial read on final call to iread' Request was from Assaf Gordon <assafgordon@HIDDEN> to control <at> debbugs.gnu.org. Full text available.
Severity set to 'wishlist' from 'normal' Request was from Assaf Gordon <assafgordon@HIDDEN> to control <at> debbugs.gnu.org. Full text available.

Message received at 28432 <at> debbugs.gnu.org:


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Subject: Re: bug#28432: dd doesn't warn about partial read on final call to
 iread
To: Barry Handelman <barry.handelman@HIDDEN>, 28432 <at> debbugs.gnu.org
References: <CAD4Br39yrmeU_r9_bfmoHMGC8XkRLdXiuM4M_M5rhRD3d=6k0Q@HIDDEN>
From: =?UTF-8?Q?P=c3=a1draig_Brady?= <P@HIDDEN>
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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.




Information forwarded to bug-coreutils@HIDDEN:
bug#28432; Package coreutils. Full text available.

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Subject: dd doesn't warn about partial read on final call to iread
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--f403045cf152ee74b705590004c8
Content-Type: text/plain; charset="UTF-8"

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.

--f403045cf152ee74b705590004c8
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div>The iread function in dd.c issues a warning if the pr=
evious read was short, suggesting that you use iflag=3Dfullblock<br></div><=
div><br></div><div>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.=C2=A0 Importantly, this will always be the case when there was only=
 one read, and it was partial.</div><div><br></div><div>I&#39;d suggest tha=
t if the strategy of warning on subsequent reads is to be used, the warning=
 routine should be run once again after the final read. =C2=A0</div></div>

--f403045cf152ee74b705590004c8--




Acknowledgement sent to Barry Handelman <barry.handelman@HIDDEN>:
New bug report received and forwarded. Copy sent to bug-coreutils@HIDDEN. Full text available.
Report forwarded to bug-coreutils@HIDDEN:
bug#28432; Package coreutils. Full text available.
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