GNU bug report logs - #79631
bug in the utility command "cut"

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

From: Michael Cornelison <mkornelix <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: bug in the utility command "cut"
Date: Wed, 15 Oct 2025 14:34:40 +0200

[Message part 1 (text/plain, inline)]

The Linux shell command: $ cut -c6- de.text > de2.text
outputs 2114 correct lines with first 5 characters removed.
From line 2115, the two characters (hex 80, hex AF) are prepended to every
output line.
The rest of each output line is correct.

I have attached the file "de.text" which triggers this bug.

I am using Ubuntu 25.04 in case that matters.

regards
Mike Cornelison

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[de.text (text/plain, attachment)]

Message #8 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Stan Marsh <gazelle <at> xmission.com>
To: bug-coreutils <at> gnu.org
Subject: bug#79631: bug in the utility command "cut"
Date: Wed, 15 Oct 2025 10:52:41 -0600

From:	Michael Cornelison
Subject:	bug#79631: bug in the utility command "cut"
Date:	Wed, 15 Oct 2025 14:34:40 +0200

>The Linux shell command: $ cut -c6- de.text > de2.text
>outputs 2114 correct lines with first 5 characters removed.
>Starting with line 2115, the two characters (hex 80, hex AF) are
>prepended to every output line.  The rest of each output line is
>correct.

>I have attached the file "de.text" which triggers this bug.

>I am using Ubuntu 25.04 in case that matters.

Those characters are in your input file (starting at line 2115).

Not a bug.

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Message #11 received at 79631 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Michael Cornelison <mkornelix <at> gmail.com>, 79631 <at> debbugs.gnu.org
Subject: Re: bug#79631: bug in the utility command "cut"
Date: Wed, 15 Oct 2025 18:41:13 +0100

On 15/10/2025 13:34, Michael Cornelison wrote:
> The Linux shell command: $ cut -c6- de.text > de2.text
> outputs 2114 correct lines with first 5 characters removed.
>  From line 2115, the two characters (hex 80, hex AF) are prepended to every
> output line.
> The rest of each output line is correct.
> 
> I have attached the file "de.text" which triggers this bug.
> 
> I am using Ubuntu 25.04 in case that matters.
> 
> regards
> Mike Cornelison

The issue is that cut(1) does not support multi-byte characters yet,
and is treating -c like -b.  This can cause cut(1) to
output a partial multi-byte character. In your case,
the following shows it starts outputting in the middle of the
UTF-8 Narrow non-breaking space character:

  LC_ALL=de_DE.UTF-8 git/coreutils/src/cut -c1-10 de.text |
   head -n2115 | tail -n1 | od -Ax -tx1z -v
  000000 33 31 30 30 e2 80 af c3 9c 62 0a                 >3100.....b.<

This is already on our TODO list.

thank you,
Padraig

Message #14 received at 79631 <at> debbugs.gnu.org (full text, mbox):

From: Collin Funk <collin.funk1 <at> gmail.com>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: 79631 <at> debbugs.gnu.org, Michael Cornelison <mkornelix <at> gmail.com>
Subject: Re: bug#79631: bug in the utility command "cut"
Date: Wed, 15 Oct 2025 21:49:36 -0700

Pádraig Brady <P <at> draigBrady.com> writes:

> The issue is that cut(1) does not support multi-byte characters yet,
> and is treating -c like -b.  This can cause cut(1) to
> output a partial multi-byte character. In your case,
> the following shows it starts outputting in the middle of the
> UTF-8 Narrow non-breaking space character:
>
>   LC_ALL=de_DE.UTF-8 git/coreutils/src/cut -c1-10 de.text |
>    head -n2115 | tail -n1 | od -Ax -tx1z -v
>   000000 33 31 30 30 e2 80 af c3 9c 62 0a                 >3100.....b.<
>
> This is already on our TODO list.

I haven't thought of a decent interface for multibyte characters that
behaves like getndelim2 yet, which is needed for 'cut'. Outside of that,
it should not be too difficult.

Collin

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