X-Recipient:	archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status:	No, hits=-2.3 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,TW_CG,T_TO_NO_BRKTS_FREEMAIL
X-Spam-Check-By:	sourceware.org
Message-ID:	<4E8B193D.4000700@gmail.com>
Date:	Tue, 04 Oct 2011 16:33:33 +0200
From:	Marco Atzeri <marco DOT atzeri AT gmail DOT com>
User-Agent:	Mozilla/5.0 (Windows NT 5.1; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1
MIME-Version:	1.0
To:	cygwin AT cygwin DOT com
Subject:	Re: 1.7.9 Missing SIGPIPE?
References:	<4E833CB4 DOT 3060004 AT lysator DOT liu DOT se> <4E8B0FC6 DOT 9050600 AT lysator DOT liu DOT se> <4E8B116D DOT 3030905 AT gmail DOT com> <20111004140927 DOT GC20825 AT ednor DOT casa DOT cgf DOT cx>
In-Reply-To:	<20111004140927.GC20825@ednor.casa.cgf.cx>
X-IsSubscribed:	yes
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

On 10/4/2011 4:09 PM, Christopher Faylor wrote:
> On Tue, Oct 04, 2011 at 04:00:13PM +0200, Marco Atzeri wrote:
>> On 10/4/2011 3:53 PM, Peter Rosin wrote:
>>> Peter Rosin skrev 2011-09-28 17:26:
>>>> Hi!
>>>>
>>>> When I use bash to build pipelines, they sometimes don't finish but
>>>> instead some process remains running. Example:
>>>>
>>>> $ tail -f -n 10000 log.txt | grep . | head -n 2
>>>>
>>>> Almost instantly I get the expected two lines of output, but no prompt
>>>> back. I have to use ctrl-c. If I don't ctrl-c I can run pstree in
>>>> another terminal and see this:
>>>>
>>>> $ pstree
>>>> ??????????mintty?????????bash?????????tail
>>>>     ??????mintty?????????bash?????????pstree
>>>
>>> This example is a poor one, as tail simply waits for a new line, when it
>>> gets a new line it forwards it to the pipe and promptly receives a
>>> SIGPIPE as grep is not there anymore.
>>>
>>> I'll get back when I have distilled a better STC. If I can...
>>
>> Hi Peter,
>> are you referring on something like SIGHUP on PTY closure ?
>>
>> http://cygwin.com/ml/cygwin/2011-07/msg00295.html
>> http://pubs.opengroup.org/onlinepubs/9699919799/functions/close.html
>
> Note that this thread contains your assertion that something isn't
> happening correctly but it isn't clear that your analysis is correct.
>
> But, no, SIGPIPE != SIGHUP and the above example clearly shows a
> completely different scenario than what is described in the above
> thread.
>
> cgf

Hi Cgf,
I know that SIGPIPE != SIGHUP, but Peter mentioned that the example
is not really representative of the PIPE problem he found, so eventually
he catched the same problem I saw on mc.
Of course, it could be a different one.

Referring to the SIGHUP thread
This portion of the standard, if I am not wrong,
it is not currently implemented in cygwin:

"If fildes refers to the master side of a pseudo-terminal, and this is 
the last close, a SIGHUP signal shall be sent to the controlling 
process, if any, for which the slave side of the pseudo-terminal is the 
controlling terminal. It is unspecified whether closing the master side 
of the pseudo-terminal flushes all queued input and output."

The workaround I implemented in mc was to send the SIGHUP to the 
subshell, before mc exit, instead on relying on cygwin to do it.

Am I misundestanding the standard ?

Regards
Marco





--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -