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.