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Re: Undocumented feature: Unnamed fifo '<(:)'

From: felix
Subject: Re: Undocumented feature: Unnamed fifo '<(:)'
Date: Thu, 8 Apr 2021 20:30:50 +0200
User-agent: Mutt/1.10.1 (2018-07-13)

Comming back on this 10month old thread...

On Tue, Jun 30, 2020 at 12:30:53PM -0400, Chet Ramey wrote:
> On 6/28/20 9:49 AM, felix wrote:
> > Bash Versions: 3.2.57(1)-release, 5.0.3(1)-release, 5.1.0(1)-alpha
> > 
> > In order to reduce forks and make some tasks a lot quicker, I run
> > forked filters as background tasks, with dedicated I/O fd.
> > 
> > For sample, to convert human datetime to UNIX SECONDS, instead of running
> > ...
> > 
> > become a lot quicker!

Found this bash mandelbrot sample at Stackoverflow:

This script take many hours to draw a mandelbrot.

Reducing number of fork to bc to only one, then same draw is done in less
than 10 minutes.

> But not guaranteed to work everywhere, especially those systems that use
> /dev/fd and pipes for this instead of FIFOs. (And lack `stdbuf'.)

Yes, to make this run under MacOS. I first dropped `stdbuf`, then because
of an ``old'' version (3.2.57(1)-release) of bash, there is the most
relevant part of my patch:
      -exec {bcout}<> <(:)
      -exec {bcin}> >(exec stdbuf -o0 bc -l >&$bcout)
      +mkfifo $fifo
      +exec 10> >(exec bc -l >$fifo)
      +exec 11<$fifo
      +rm $fifo

You could have a look:

> > There is maybe something to document or even create a new feature
> > about open2 and open3...

I was wrong about ``open2'', there is already ``coproc''.

But about ``open3'' permitting to pass all 3 STDIN STDOUT and STDERR,
there is maybe something to do!?

 Félix Hauri  -  <felix@f-hauri.ch>  -  http://www.f-hauri.ch

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