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Date:      11 Apr 1999 01:57:10 -0500
From:      Joel Ray Holveck <joelh@gnu.org>
To:        Leif Neland <leifn@neland.dk>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: Baud rate of 0
Message-ID:  <86emlrzltl.fsf@detlev.UUCP>
In-Reply-To: Leif Neland's message of "Sun, 11 Apr 1999 08:36:51 %2B0200 (CEST)"
References:  <Pine.BSF.4.05.9904110833350.99823-100000@arnold.neland.dk>

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>> Why does setting the baud rate of a (wired tty) connection to 0
>> terminate it?  When is this useful?
> Why shouldn't it? 
> How else would you terminate it?

As a program or a user?

From a program's perspective, init uses revoke(2) to terminate it;
this seems to be the most effective way.  I'm not sure how revoke is
implemented in the kernel, though; it may involve frobbing the baud
rate at some point.

If you're talking about doing this as a user, then I suppose that
'stty 0 < /dev/ttyS1' would do that, although is not really terribly
general since it doesn't work on net connections.

> Or rather, it is easier to do it this way, than to find pid's
> running on that line, and kill 'em separately.

Yes, that is true, although killing the process group leader seems to
be generally effective as well.

> I could think of many reasons for wanting to terminate a terminal
> session.

So can I.  I just don't see why that would be a useful manner to do
this.

Cheers,
joelh

-- 
Joel Ray Holveck - joelh@gnu.org
   Fourth law of programming:
   Anything that can go wrong wi
sendmail: segmentation violation - core dumped


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