GNU bug report logs - #69901
(echo a; echo b) | sort -nu looses some data

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Rafal Maszkowski <rzm <at> icm.edu.pl>
To: bug-coreutils <at> gnu.org
Subject: (echo a; echo b) | sort -nu  looses some data
Date: Tue, 19 Mar 2024 16:33:09 +0100

Sort with -n and -u options works correctly for numbers:

(echo 10; echo 11) | sort -nu
10
11

but looses data when used with non-numbers:

(echo a; echo b) | sort -nu
a

(echo 1.0; echo 1.1) | sort -nu
1.0

I have tested this on versions 8.32 and 9.2 default for Debian 11 and
12, and additionally compiled version 9.4. The --debug option advised in
README does not say anything helpful:

(echo a; echo b) | sort --debug -nu
sort: text ordering performed using simple byte comparison
a
^ no match for key

R.
-- 
„Walczy on z całym zapamiętaniem przeciwko intelektowi” - z akt personalnych prof. A. Baeumlera

Message #10 received at 69901-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Rafal Maszkowski <rzm <at> icm.edu.pl>
Cc: 69901-done <at> debbugs.gnu.org
Subject: Re: bug#69901: (echo a; echo b) | sort -nu looses some data
Date: Tue, 19 Mar 2024 15:07:01 -0700

On 3/19/24 08:33, Rafal Maszkowski wrote:
> he --debug option advised in
> README does not say anything helpful:
> 
> (echo a; echo b) | sort --debug -nu
> sort: text ordering performed using simple byte comparison
> a
> ^ no match for key

That diagnostic message is helpful. It's telling you that there's no 
number, so everything sorts as being the same, which means 'sort -nu' 
(correctly) outputs just one line.

'sort' has behaved this way for quite some time, and POSIX requires this 
behavior.

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