GNU bug report logs - #46048
split -n K/N loses data, sum of output files is smaller than input file.

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Pádraig Brady <P <at> draigBrady.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#46048: closed (split -n K/N loses data, sum of output files
 is smaller than input file.)
Date: Mon, 25 Jan 2021 14:22:02 +0000

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Your message dated Mon, 25 Jan 2021 14:21:35 +0000
with message-id <4f858cd0-19e4-d159-c2e7-51b3aad0b3b0 <at> draigBrady.com>
and subject line Re: bug#46048: split -n K/N loses data, sum of output files is smaller than input file.
has caused the debbugs.gnu.org bug report #46048,
regarding split -n K/N loses data, sum of output files is smaller than input file.
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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46048: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=46048
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From: Paul Hirst <contact <at> phirst.org>
To: bug-coreutils <at> gnu.org
Subject: split -n K/N loses data,
 sum of output files is smaller than input file.
Date: Fri, 22 Jan 2021 18:58:03 -1000

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split --number K/N appears to lose data in, with the sum of the sizes of
the output files being smaller than the original input file by 131072 bytes.

$ split --version
split (GNU coreutils) 8.30
...

$ head -c 1000000 < /dev/urandom > test.dat
$ split --number=1/4 test.dat > t1
$ split --number=2/4 test.dat > t2
$ split --number=3/4 test.dat > t3
$ split --number=4/4 test.dat > t4

$ ls -l
-rw-r--r-- 1 user user  250000 Jan 22 18:36 t1
-rw-r--r-- 1 user user  250000 Jan 22 18:36 t2
-rw-r--r-- 1 user user  250000 Jan 22 18:36 t3
-rw-r--r-- 1 user user  118928 Jan 22 18:36 t4
-rw-r--r-- 1 user user 1000000 Jan 22 18:33 test.dat

Surely this should not be the case?

Paul

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From: Pádraig Brady <P <at> draigBrady.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: Paul Hirst <contact <at> phirst.org>, 46048-done <at> debbugs.gnu.org
Subject: Re: bug#46048: split -n K/N loses data, sum of output files is
 smaller than input file.
Date: Mon, 25 Jan 2021 14:21:35 +0000

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On 24/01/2021 19:55, Paul Eggert wrote:
> On 1/24/21 8:52 AM, Pádraig Brady wrote:
>> -      if (lseek (STDIN_FILENO, start, SEEK_CUR) < 0)
>> +      if (lseek (STDIN_FILENO, start, SEEK_SET) < 0)
> 
> Dumb question: will this handle the case where you're splitting from
> stdin and stdin is a seekable file and its initial file offset is nonzero?

Right. Following on the logic from input_file_size(),
I'm going with the attached, which I'll push later.
Marking this as done.

thanks,
Pádraig

[split-k_of_n.patch (text/x-patch, attachment)]

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