From: lm@mcvoy.com (Larry McVoy)
Subject: [TUHS] Excise process from a pipe
Date: Thu, 10 Jul 2014 07:45:03 -0700 [thread overview]
Message-ID: <20140710144502.GA24876@mcvoy.com> (raw)
In-Reply-To: <201407101204.s6AC4hKQ026601@coolidge.cs.dartmouth.edu>
I'm pretty aware of the various flavors of Unix and unless the process
in question is willing to help I can't see how this could work.
There are system calls for passing file descriptors but you have the
problem that the pipe itself is a buffer of some size and you'd have
the problem of draining it.
Every utility that you put in a pipeline would have to be reworked
to pass file descriptors around, it would be really unpleasant and
not at all Unix like.
On Thu, Jul 10, 2014 at 08:04:43AM -0400, Doug McIlroy wrote:
> In the suggested answer, the code changes but the process survives.
>
> I suspect the answer to my original question is no, but I know only a tiny
> fraction of the cumulative API of the extended Unix family.
>
> Doug
>
> >> Was there ever a
> >> flavor of Unix in which a process could excise itself
> >> from a pipeline without breaking the pipeline?
> >
> > If in the middle of a pipeline, all I can think of is:
> >
> > close fd 0 and fd 1
> > dup() read end of pipe 1 to be stdin (fd 0)
> > dup() write end of pipe 2 to be stdout (fd 1)
> > exec("/bin/cat")
> _______________________________________________
> TUHS mailing list
> TUHS at minnie.tuhs.org
> https://minnie.tuhs.org/mailman/listinfo/tuhs
--
---
Larry McVoy lm at mcvoy.com http://www.mcvoy.com/lm
next prev parent reply other threads:[~2014-07-10 14:45 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-10 2:49 [TUHS] Subject:unpipeIt'seasy for a process to insert a new process intoapipelineeither upstream or down unpipe Doug McIlroy
2014-07-10 4:52 ` [TUHS] Excise process from a pipe Warren Toomey
2014-07-10 5:00 ` Dave Horsfall
2014-07-10 5:06 ` Christopher Vance
2014-07-10 8:43 ` Warren Toomey
2014-07-10 12:03 ` Doug McIlroy
2014-07-10 12:04 ` Doug McIlroy
2014-07-10 14:45 ` Larry McVoy [this message]
2014-07-10 15:10 Noel Chiappa
2014-07-10 15:11 ` Larry McVoy
2014-07-10 16:06 Noel Chiappa
2014-07-10 16:04 ` Larry McVoy
2014-07-10 16:12 Noel Chiappa
2014-07-14 14:13 Doug McIlroy
2014-07-14 15:12 Noel Chiappa
2014-07-16 21:31 Noel Chiappa
2014-07-17 15:42 Noel Chiappa
2014-07-18 15:33 Noel Chiappa
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