Date: Tue, 14 May 1996 10:20:44 +0100 From: tom@uces.bangor.ac.uk (Tom Crummey (ADM)) To: freebsd-hackers@freebsd.org Subject: write and pty's Message-ID: <199605140920.KAA04825@newton.uces>
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Hello,
I sent this message to freebsd-questions, but it is probably better on
this list.
If you do reply to this, could you copy to me directly as I'm not on the
hackers list (yet).
Thanks.
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From: Tom Crummey (ADM) <tom>
Subject: write and pty's
To: freebsd-questions@freebsd.org
Date: Thu, 9 May 96 23:29:56 BST
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Hello,
I have been trying to track down a problem in the xview library code
which causes the cmdtool program to continuously output to the pty
it is using. For example, start a cmdtool and type return. You will
get a continuous stream of prompts as if you were continually typing
the return key.
After some hours with xxgdb and libraries compiled with debugging symbols,
I tracked the problem to a write call. This write call returns 0 even
though it appears that a charater has been written. The fact that this
call returns 0 means that the write pointer in the cmdtool code is not
updated and so it is written again etc. (you get the picture)
It seems that there is a problem with the write system call returning 0
instead of the number of characters written in this particular case.
The pty is supposedly not in remote mode.
Does anyone have any idea why the write call would return 0 even when
characters have been written? Could anyone who knows the pty kernel
code comment?
I can send the segment of code involved, but I suspect it won't help
as there is too much context requried to see what is going on.
I think I might be getting slightly out of my depth.....
glug ..glug...
I am running FreeBSD-2.2-SNAP 960128 with the xview-3.2 patched for X11R6.
The problem also exists on 2.1-RELEASE.
--
Tom.
----------------------------------------------------------------------------
Tom Crummey, EMAIL: tom@uces.bangor.ac.uk | /\
University of Wales, Bangor, | / \/\
Unit for Coastal and Estuarine Studies, | /\/ \ \
Ynys Faelog, Menai Bridge, TEL: +44 (0)1248 713808 |/ ======\=\
Gwynedd, LL59 5EY, U.K. FAX: +44 (0)1248 716729 | B A N G O R
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