X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; q=dns; s=
	default; b=ERiwvpnERj9x42Zw4w5ZZKwnTFLKw52x3R7F6gzof01CE8gJC0NBL
	GlWQOQS99r4XMM1Eo9i194PUzHKpAwZzPx9wwBb/FbweDF5pIb5xSsrL8GqN1N48
	CHKAH3GpgZ5H9v93OKorXPAorFH8DQzeQDdtE2evXTTovTJzJf7dwQ=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; s=default;
	bh=gb0+7Rqh6qhTqbmTsFiCjk9tDEU=; b=S1Bo/ZRDNW8cdWN1mMDSlPYCXVvR
	oMGc/L5+I+xQ4UYZFHCDnhUnmMCc46ra6Fwi1bX0Iyh+cmvdh8QwR3mzIjOUx/SK
	WNItUM9L0pF1ERDx+1uVBBpUnGs33Aca2LgHYAlnMqG4whZVf9ACrrx2slC7/VfY
	VJspmoLHt/TYYe8=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
Authentication-Results:	sourceware.org; auth=none
X-Virus-Found:	No
X-Spam-SWARE-Status:	No, score=-101.2 required=5.0 tests=AWL,BAYES_50,KAM_LAZY_DOMAIN_SECURITY,KHOP_DYNAMIC,RCVD_IN_BRBL_LASTEXT,RCVD_IN_PBL,RDNS_DYNAMIC,USER_IN_WHITELIST autolearn=no version=3.3.2 spammy=Maintainer, DOT, Ken, H*r:500
X-HELO:	calimero.vinschen.de
Date:	Fri, 8 Jan 2016 21:50:08 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Problem with named pipes
Message-ID:	<20160108205008.GM20447@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<567DB7AB DOT 5060606 AT cornell DOT edu>
MIME-Version:	1.0
In-Reply-To:	<567DB7AB.5060606@cornell.edu>
User-Agent:	Mutt/1.5.24 (2015-08-30)

--yklP1rR72f9kjNtc
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Dec 25 16:39, Ken Brown wrote:
> I've noticed a difference between Cygwin and Linux involving named pipes.=
  I
> don't know if this a bug or simply a difference.
>=20
> Consider the following two scripts:
>=20
> $ cat fifo1.sh
> #!/bin/sh
> set -x
> rm -f foo
> mkfifo foo
> exec 7>foo
> echo blah > foo
>=20
> $ cat fifo2.sh
> #!/bin/sh
> set -x
> read bar < foo
> echo $bar
>=20
> I run fifo1.sh in Terminal 1 and get the following on both Cygwin and Lin=
ux:
>=20
> [Terminal 1]
> $ ./fifo1.sh
> + rm -f foo
> + mkfifo foo
> + exec
>=20
> The call to echo in the next line blocks, because foo has not yet been
> opened for reading.  Now I run fifo2.sh in Terminal 2.  On Linux, the "re=
ad"
> in fifo2.sh unblocks fifo1.sh, and I see the following:
>=20
> [Terminal 1, Linux]
> $ ./fifo1.sh
> + rm -f foo
> + mkfifo foo
> + exec
> + echo blah
>=20
> [Terminal 2, Linux]
> $ ./fifo2.sh
> + read bar
> + echo blah
> blah
>=20
> On Cygwin, however, Terminal 1 remains blocked, and Terminal 2 is blocked
> when it tries to read:
>=20
> [Terminal 2, Cygwin]
> $ ./fifo2.sh
> + read bar
>=20
> The problem disappears if I remove the line "exec 7>foo" from fifo1.sh.  =
The
> problem also disappears if I leave that line in, but change the last line=
 to
> "echo blah >&7".

Very tricky problem.  The FIFO code falls over its own feet trying to
handle more than one writer (exec 7> is the first, echo blah is the
second writer).  Sigh.  This code needs a thorough rewrite...


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

--yklP1rR72f9kjNtc
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2
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=SlzT
-----END PGP SIGNATURE-----

--yklP1rR72f9kjNtc--

- Raw text -