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Path: utzoo!lsuc!dave
From: dave@lsuc.UUCP (David Sherman)
Newsgroups: net.unix-wizards,net.dcom
Subject: any harm in allowing only ctrl-Q to restart output?
Message-ID: <247@lsuc.UUCP>
Date: Sun, 30-Dec-84 14:21:00 EST
Article-I.D.: lsuc.247
Posted: Sun Dec 30 14:21:00 1984
Date-Received: Sun, 30-Dec-84 16:02:38 EST
Organization: Law Society of Upper Canada, Toronto
Lines: 31

Almost all of the terminals on our UNIX system are VT-100-compatible
Esprit terminals. They have a NO SCROLL key which transmits ctrl-S
and stops terminal output locally. The terminal will only restart on
receipt of a ctrl-Q.

If you press the NO SCROLL key (which, incidentally, is easy to do
by accident on these terminals), UNIX will see the ctrl-S and stop;
but then _any_ key will let UNIX restart, not just ctrl-Q. This means
data can be lost, if you press NO SCROLL, any other key, and then
wait a bit before ctrl-Q -- UNIX starts resending, but the terminal
won't display it until it gets the ctrl-Q (or you press NO SCROLL again).

I'd like to change UNIX to require ctrl-Q (actually t_startc)
to restart output. With our terminals, it can only improve things -
as it is, users have to know to press the NO SCROLL again (or hit
ctrl-Q explicitly). Is this likely to cause any problems anywhere
else?

We're running v7 on a Perkin-Elmer 3220, by the way. The change is
trivial - commenting out two lines in /usr/sys/dev/tty.c.

As an alternative, I'm thinking of creating a new ioctl setting
(TIOCQSTART?) which controls this behaviour, so it's user-settable.
Any comments on that idea?

Dave Sherman
The Law Society of Upper Canada
Toronto
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