GNU bug report logs - #35046
[PATCH] factor: check the standard output instead of the standard input

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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#35046: closed ([PATCH] factor: check the standard output
 instead of the standard input)
Date: Sun, 31 Mar 2019 22:54:03 +0000

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Your message dated Sun, 31 Mar 2019 15:53:44 -0700
with message-id <67639d78-6c96-9935-be03-f148cadf4508 <at> draigBrady.com>
and subject line Re: bug#35046: [PATCH] factor: check the standard output instead of the standard input
has caused the debbugs.gnu.org bug report #35046,
regarding [PATCH] factor: check the standard output instead of the standard input
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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35046: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=35046
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From: Shugo Maeda <shugo <at> ruby-lang.org>
To: bug-coreutils <at> gnu.org
Subject: [PATCH] factor: check the standard output instead of the standard
 input
Date: Sat, 30 Mar 2019 15:43:17 +0900

* src/factor.c (lbuf_putc): Use line buffered mode if the standard
output (not the standard input) is a terminal in the same way as the
stdio library.  User programs might use pty only for the standard out
like the example of Ruby's PTY module:
https://docs.ruby-lang.org/en/2.6.0/PTY.html#module-PTY-label-Example
---
 src/factor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/factor.c b/src/factor.c
index 39e8918ff..173774045 100644
--- a/src/factor.c
+++ b/src/factor.c
@@ -2403,7 +2403,7 @@ lbuf_putc (char c)
       /* Provide immediate output for interactive input.  */
       static int line_buffered = -1;
       if (line_buffered == -1)
-        line_buffered = isatty (STDIN_FILENO);
+        line_buffered = isatty (STDOUT_FILENO);
       if (line_buffered)
         lbuf_flush ();
       else if (buffered >= FACTOR_PIPE_BUF)
-- 
2.11.0

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From: Pádraig Brady <P <at> draigBrady.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>, Shugo Maeda <shugo <at> ruby-lang.org>,
 35046-done <at> debbugs.gnu.org
Subject: Re: bug#35046: [PATCH] factor: check the standard output instead of
 the standard input
Date: Sun, 31 Mar 2019 15:53:44 -0700

On 30/03/19 22:14, Paul Eggert wrote:
> Pádraig Brady wrote:
>>> -        line_buffered = isatty (STDIN_FILENO);
>>> +        line_buffered = isatty (STDOUT_FILENO);
>>>         if (line_buffered)
>>>           lbuf_flush ();
>>>         else if (buffered >= FACTOR_PIPE_BUF)
>> That would impact use cases like:
>>
>>    factor | sed -u 's/.*: *//'
> 
> Sure, but the longstanding tradition for almost all GNU utilities is for stdout 
> to be line-buffered if it is a tty (regardless of whether stdin is a tty), and 
> that's how 'factor' behaved until we started fooling with buffering in coreutils 
> 8.24. Shouldn't we simply go back to the longstanding tradition for deciding 
> whether to line-buffer stdout? Surely factor's current behavior is simply a bug 
> introduced in 8.24 and not fixed in 8.26.

I should be clearer, sorry.

I think this could be improved.
I've pushed the change to set line_buffered if either stdin or stdout isatty():
https://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=6d78a28

I was wondering if there was a practical use case that this impacted.
Enough justification was provided in the commit message which I didn't read fully.

The original buffering adjustments were so that parallel invocations of factor,
output lines atomically, which factor is able to achieve given its restricted output format.

Marking this as done.

thanks,
Pádraig

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