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:mime-version:content-type
	:content-transfer-encoding:date:from:to:subject:message-id; q=
	dns; s=default; b=a5Ml/K7uZMMUPHmX0nUSgeGHMBR+QV4cKKmRpPpFcx/giv
	w+9EIoNBNwxw3aXMrTKe/VqV31Gu+9tZv4owj9Pbv4PeJ3zl7IzIBX7VfU4fVdww
	qPE5N6oG8I8MteXlZ3SeYVuBesJqOEpfbFL8wgSBzq8iF6xUq6NXuWq9O1IAc=
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:mime-version:content-type
	:content-transfer-encoding:date:from:to:subject:message-id; s=
	default; bh=Czt0AQChjPutsNpS015ujzbOD5Y=; b=UUDnkRSqAg0asjPZW7LL
	y0st6VMSSTI5X33qFqz2WhsduXHyu1P7KYlMyXoO7exIZsTDJlrn+6a03dRS7mKQ
	cA/Iqa1fjLwShGMuVIQWjEFE5CrBG2nAdtX8AYpiU0Q+O8MB3GYe/+zskR/fuDoK
	mFRLiyNl/es/JkYo4TOpVNc=
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=-1.9 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 spammy=prof, stc, Hx-languages-length:2775, H*UA:Webmail
X-HELO:	lb3-smtp-cloud6.xs4all.net
MIME-Version:	1.0
Date:	Mon, 04 Jan 2016 09:03:27 +0100
From:	Houder <houder AT xs4all DOT nl>
To:	cygwin AT cygwin DOT com
Subject:	Pipes Again -- a simple test case
Message-ID:	<0aebd09993901f3ef3ff728d162952cd@xs4all.nl>
X-Sender:	houder AT xs4all DOT nl (y6MmNL6PIptlWVGaBZnimw==)
User-Agent:	XS4ALL Webmail
X-IsSubscribed:	yes

Hi Corinna,

I have been looking for an STC to show why cmp fails on Cygwin (and to 
show the
difference between Cygwin and Linux).

The STC below creates a pipe (pipe() is used), followed by calls to 
fstat() and
stat() for both the read end and the write end of the pipe.

(I also tested with popen()/pclose(): same result)

Regards,
Henri

Btw, I am using W7 prof.; Cygwin-32 and Cygwin-64; 2.3.1 and 2.4.0

=====

The code for the STC is basically as follows:

int
main()
{
     struct stat sb[2];
     int pfd[2];

     pid_t pid = getpid();
     if (pipe(pfd) != 0)
         errExit("pipe");

     for (int f = 0; f < 2; f++) // step over the read end and write end 
of the pipe
     {
         char symlnk[64];

         if (sprintf(symlnk, "/proc/%d/fd/%d", pid, pfd[0 + f]) <= 0)
             errExit("sprintf");
         !f ? printf("... %s (symbolic link to the  read end of the 
pipe)\n", symlnk)
            : printf("... %s (symbolic link to the write end of the 
pipe)\n", symlnk);

         printf("... using  stat()\n");
         if (stat(symlnk, sb) != 0)
             errExit("stat");
         displayStatInfo(sb);

         printf("... using fstat()\n");
         if ( fstat(pfd[0 + f], sb + 1) != 0 )
             errExit("fstat");
         displayStatInfo(sb + 1);
     }
     exit(EXIT_SUCCESS);
}

Linux shows:
@@ ./t_stat2
... /proc/968/fd/3 (symbolic link to the  read end of the pipe)
... using  stat()
File type:                FIFO or pipe
Device containing i-node: (8)   major=0   minor=8
I-node number:            53bc - decimal: 21436
File size:                0 bytes
... using  stat()
File type:                FIFO or pipe
Device containing i-node: (8)   major=0   minor=8
I-node number:            53bc - decimal: 21436
File size:                0 bytes
... /proc/968/fd/4 (symbolic link to the write end of the pipe)
... using  stat()
File type:                FIFO or pipe
Device containing i-node: (8)   major=0   minor=8
I-node number:            53bc - decimal: 21436
File size:                0 bytes
... using  stat()
File type:                FIFO or pipe
Device containing i-node: (8)   major=0   minor=8
I-node number:            53bc - decimal: 21436
File size:                0 bytes

Cygwin shows:
@@ ./t_stat2
... /proc/2864/fd/3 (symbolic link to the  read end of the pipe)
... using  stat()
File type:                FIFO or pipe
Device containing i-node: (c7)   major=0   minor=199
I-node number:            a325e1ba495b63cf - decimal: 
11756050592531440591
File size:                0 bytes
... using fstat()
File type:                FIFO or pipe
Device containing i-node: (c6)   major=0   minor=198
I-node number:            0 - decimal: 0              <==== zero, the 
non-existing i-node ...
File size:                0 bytes
... /proc/2864/fd/4 (symbolic link to the write end of the pipe)
... using  stat()
File type:                FIFO or pipe
Device containing i-node: (c7)   major=0   minor=199
I-node number:            a325e1ba495f64cb - decimal: 
11756050592531702987 <==== Linux shows the same i-node
File size:                0 bytes
... using fstat()
File type:                FIFO or pipe
Device containing i-node: (c5)   major=0   minor=197
I-node number:            0 - decimal: 0              <==== ditto
File size:                0 bytes

=====

--
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 -