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Date: Mon, 2 May 2005 10:30:40 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: cygwin AT cygwin DOT com
Subject: Re: cygwin-1.5.16-1: FIFOs broken
In-Reply-To: <20050501052345.GA25851@trixie.casa.cgf.cx>
Message-ID: <Pine.GSO.4.61.0505021023430.5266@slinky.cs.nyu.edu>
References: <427424F9 DOT 8060209 AT 1979 DOT usna DOT com> <20050501010945 DOT GB21071 AT trixie DOT casa DOT cgf DOT cx> <42743E33 DOT 1020700 AT 1979 DOT usna DOT com> <d51ftk$vj9$1 AT sea DOT gmane DOT org> <20050501052345 DOT GA25851 AT trixie DOT casa DOT cgf DOT cx>
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On Sun, 1 May 2005, Christopher Faylor wrote:

> On Sat, Apr 30, 2005 at 09:52:28PM -0500, Ren? Berber wrote:
> >Jerry D. Hedden wrote:
> >[snip]
> >>> However, that said, the above WJFFM.  In fact, it works more like linux
> >>> in 1.5.16 than it does on 1.5.15, i.e., the cat command exits after
> >>> printing "YOUR TEXT HERE" whereas it continues to block in 1.5.15.
> >>
> >> I tried the 4/30 snapshot of cygwin1.dll.  It exhibited the behavior you
> >> mentioned with the 'cat' exiting after it reads text.  However, this is
> >> a bad thing.  It means that the FIFO is being set EOF after there is no
> >> more data.  I tried my client-server app with the snapshot cygwin1.dll,
> >> and it failed because of this.
> >>
> >> It seems to me that the behavior of FIFOs under 1.5.15 was correct, and
> >> that under both 1.5.16 and the snapshot, FIFOs are now broken.
> >
> >FWIW, I just tested your example under Solaris 8 and it works just like
> >Christopher describes.
>
> I think the previous <1.5.15 implementation of fifos represented my
> ever-evolving understanding of how they are supposed to work.  Either
> that or it was just a bug.
>
> (FWIW, I just tried the example on another machine and still see success
> with 1.5.16.)
>
> If you want to more-or-less duplicate the behavior of 1.5.15 you can do
> something like this:
>
> (echo 99999&; echo YOUR TEXT HERE) > /tmp/FIFO

This is pretty obvious from the context and the following paragraph, but
just to clarify for the archives: the above should be

(sleep 99999&; echo YOUR TEXT HERE) > /tmp/FIFO

> As long as there is something sitting around which has the fifo open,
> the cat process will not terminate.  Of course, there will be a long
> running sleep process sitting around in the above example and that
> may not be desirable.  So, there may be a more elegant way to do this.
>
> I thought that maybe something like:
>
> cat < FIFO 42>FIFO
>
> might work since that would cause cat to keep FIFO open for input and
> output but that just hangs on both cygwin and linux.

Interestingly enough,

cat <>/tmp/FIFO

seems to work for me on RH7.3 (kernel 2.4.18-3, bash 2.05a).
	Igor
-- 
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