6 Dec
2024
6 Dec
'24
4:03 a.m.
On Thu, Dec 5, 2024 at 2:13 PM Dan Cross <crossd(a)gmail.com> wrote:
On Thu, Dec 5, 2024 at 3:56 PM
<arnold(a)skeeve.com> wrote:
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
Chet Ramey via TUHS <tuhs(a)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.