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From: Warner Losh <imp@bsdimp.com>
To: Dan Cross <crossd@gmail.com>
Cc: johnl@taugh.com, tuhs@tuhs.org, marc.donner@gmail.com
Subject: [TUHS] Re: Pipes (was Re: After 50 years, what has the Impact of Unix been?)
Date: Thu, 5 Dec 2024 15:03:18 -0700	[thread overview]
Message-ID: <CANCZdfouq4PKaGUNtLdDOUN2Bm4g4qw+2CTumwHFjjY=BZMy8g@mail.gmail.com> (raw)
In-Reply-To: <CAEoi9W4WAb9JO8VAPpHH9eB0=-EnJr0MySt_YH_eTUdTERqoUw@mail.gmail.com>

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On Thu, Dec 5, 2024 at 2:13 PM Dan Cross <crossd@gmail.com> wrote:

> On Thu, Dec 5, 2024 at 3:56 PM <arnold@skeeve.com> wrote:
> > Chet Ramey via TUHS <tuhs@tuhs.org> wrote:
> > > On 12/5/24 10:19 AM, Dan Cross wrote:
> > >
> > > > Unix pipelines, on the other hand, tend to be used in a manner that
> is
> > > > strictly linear, without the fan-out and fan-in capabilities
> described
> > > > by Morrison. Of course, nothing prevents one from building a
> > > > Morrison-style "network" from Unix processes and pipes, though it's
> > > > hard to see how that would work without something like `select`,
> which
> > > > didn't yet exist in 1978. Regardless, Unix still doesn't expose a
> > > > particularly convenient syntax for expressing these sorts of
> > > > constructions at the shell.
> > >
> > > Process substitution is about as close as we can get, but most programs
> > > still process their filename arguments one at a time, beginning to end.
> > >
> > > The canonical process substitution example is
> > >
> > >       diff <(old-program-version) <(new-program-version)
> > >
> > > to do simple regression testing.
> >
> > And fanout is simply
> >
> >         ... | tee >(pipeline1) >(pipeline2)
>
> And indeed these things are pretty nifty, but don't they generate
> trees, and not arbitrary dags? They don't quite capture the full
> generality of Morrison-style networks since it doesn't seem like
> there's a way to connect process substitution fan-out with fan-in; at
> least, not conveniently.
>
> It is, perhaps, notable that Go allows me to do this sort of thing
> with channels and goroutines, but it has `select` built into the
> language.
>
> Funny, despite using Unix almost daily for over 30 years now, I don't
> think I've ever felt limited by the power of pipelines. On the
> contrary, I've lost count of the times I've felt limited on systems
> that do Not support pipes.
>

The <() , >()  syntax is a bash extension. Not all shells support it. And
I couldn't find them in POSIX Issue 8.

Warner

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  parent reply	other threads:[~2024-12-05 22:03 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-12-04  3:17 [TUHS] After 50 years, what has the Impact of Unix been? sjenkin
2024-12-04 13:05 ` [TUHS] " Marc Donner
2024-12-04 13:40   ` William Cheswick
2024-12-04 15:02   ` Rich Salz
2024-12-05  3:08   ` John Levine
2024-12-05 15:19     ` [TUHS] Re: Pipes (was Re: After 50 years, what has the Impact of Unix been?) Dan Cross
2024-12-05 16:00       ` John R Levine
2024-12-05 16:17         ` Heinz Lycklama
2024-12-05 17:06           ` Marc Rochkind
2024-12-05 17:53             ` John Cowan
2024-12-05 18:05             ` John Levine
2024-12-05 17:22           ` Paul Winalski
2024-12-05 18:19         ` Ron Natalie
2024-12-06  2:29           ` Adam Thornton
2024-12-07 20:38             ` Ron Natalie
2024-12-05 16:55       ` Adam Thornton
2024-12-05 17:35       ` Chet Ramey via TUHS
2024-12-05 20:55         ` arnold
2024-12-05 21:12           ` Dan Cross
2024-12-05 21:50             ` Marc Rochkind
2024-12-05 22:03             ` Warner Losh [this message]
2024-12-05 22:19               ` Chet Ramey via TUHS
2024-12-05 23:07                 ` Marc Rochkind
2024-12-06  8:16                   ` Diomidis Spinellis
2024-12-06  0:46                 ` Alexis
2024-12-06 21:46                   ` Chet Ramey via TUHS
2024-12-05 23:07               ` arnold
2024-12-06  1:09                 ` G. Branden Robinson
2024-12-06  1:31                   ` Greg A. Woods
2024-12-06  2:05                     ` Steve Nickolas
2024-12-06 16:44                     ` arnold
2024-12-05 22:05             ` Bakul Shah via TUHS
2024-12-06  2:02             ` John Levine
2024-12-06  2:21               ` Dan Cross
2024-12-06 16:46                 ` arnold
2024-12-06  2:26 Douglas McIlroy

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