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From: worley@alum.mit.edu (Dale R. Worley)
Newsgroups: gnu.bash.bug
Subject: Re: Proposed new feature for bash:  unbuffered pipes, part 1: overview
Date: Wed, 22 Apr 2020 21:16:53 -0400
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Greg Wooledge <wooledg@eeg.ccf.org> writes:
> On Tue, Apr 21, 2020 at 08:38:41PM -0400, Dale R. Worley wrote:
>> The "unbuffered pipe" symbol ">|>" causes Bash to set in the
>> environment of the "grep" process a variable "STDOUT_UNBUFFERED" with
>> a value that contains the dev and ino values for the pipe which the
>> "grep" process sees as fd 1.
>
> Which libc implements this?

None does yet, obviously.  That's why I provided a patch for it.

>> References
>> 
>> 14 Sep 1999
>> https://marc.info/?l=glibc-bug&m=98313957306295&w=4
>> "[REMINDER] stdio buffer flushing control environment variable"
>
> The next message in the thread is from Ulrich Drepper, saying:
>
>   I will not implement this since it's completely up to the application
>   to do this.  One knows in advance when this is necessary.  If there is
>   a problem with the current code to select when line-buffering is used
>   (we use as everybody else isatty) then one can talk about this.  I
>   think it is correct, though.

That's true, but I don't hink he's looking at it properly.  It was also
from 20 years ago.

Dale