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Re: bug#8490: dd reads random number of records from pipes - named or ot

From: Pádraig Brady
Subject: Re: bug#8490: dd reads random number of records from pipes - named or otherwise - coreutils 8.9
Date: Wed, 13 Apr 2011 15:51:55 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20100227 Thunderbird/3.0.3

On 12/04/11 22:02, Jesse Gordon wrote:
> I can't believe such an obvious bug would exist this long, but on the
> other hand the test is so simple I can't see where it's user error.
> dd, when reading from stdin or from a named pipe sometimes (but not
> always) reads a random number of records a bit less then what it should.
> I tried it like /dev/zero|dd, like yes|dd, cat somefile|dd, and even 
> mkfifo pip; yes > pipe & dd if=pipe -- and all sometimes failed.
> However, if=arealfile seems to always work perfectly.
> To replicate:
> yes|dd bs=1000 count=1000|wc -c

Eric's email crossed with mine and won the race to close this,
hence resending reply to main list...

With the about to be released coreutils, we now warn about this:

$ yes|dd bs=1000 count=1000|wc -c
dd: warning: partial read (960 bytes); suggest iflag=fullblock

We can't do that by default for backwards compat reasons.


p.s. I just noticed that this is not in NEWS.
I'll fix that now...

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