GNU bug report logs - #76255
cat: error without arguments

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: lilydjwg <lilydjwg <at> gmail.com>
Subject: bug#76256: closed (Re: bug#76255: cat: error without arguments)
Date: Sat, 15 Feb 2025 06:23:03 +0000

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Your bug report

#76255: cat: error without arguments

which was filed against the coreutils package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 76256 <at> debbugs.gnu.org.

-- 
76255: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=76255
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: lilydjwg <lilydjwg <at> gmail.com>
Cc: 76255-done <at> debbugs.gnu.org
Subject: Re: bug#76255: cat: error without arguments
Date: Fri, 14 Feb 2025 22:22:02 -0800

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On 2025-02-12 22:45, lilydjwg wrote:
> cat: -: input file is output file

Thanks for the bug report. The symptoms you observe are a bug in 'cat'. 
I also see a bug in Gawk which I reported to the Gawk maintainer 
<https://lists.gnu.org/r/bug-gawk/2025-02/msg00003.html>. I don't see a 
bug in zsh or fish but perhaps I'm missing something.

To fix the 'cat' bug I installed the attached patch into bleeding-edge 
Coreutils on Savannah, and something like this patch should appear in 
the next release.

[0001-cat-fix-plain-cat-bug.patch (text/x-patch, attachment)]

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From: lilydjwg <lilydjwg <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: Re: cat: error without arguments
Date: Thu, 13 Feb 2025 15:13:58 +0800

On Thu, Feb 13, 2025 at 02:45:39PM +0800, lilydjwg wrote:
> In the past I can run `cat` without any arguments and it prints
> whatever I type at the terminal. However since 9.6, `cat` reports the
> following error:
> 
> cat: -: input file is output file

Ah, I find it's not always reproducible, and a strace reveals that the
stdout flags are different:

Erroring cat (in my existing shell session):

fcntl(1</dev/pts/5<char 136:5>>, F_GETFL) = 0x402 (flags O_RDWR|O_APPEND)

Working cat (in a new shell session):

fcntl(1</dev/pts/11<char 136:11>>, F_GETFL) = 0x2 (flags O_RDWR)

I'm using zsh, and this issue starts to occur after I do a tab
completion (in my case, type "cat" and then tab). Other users report
that some fish completion can also cause this issue.

The terminal in use itself seems to not matter. I'm using GNOME
Terminal, inside and outside tmux.

-- 
Best regards,
lilydjwg

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