watch(8), xwatchwin as courseware [solved by script/tail]

Andrew Reitz ajr9 at
Mon Apr 3 06:42:51 UTC 2006

On Apr 2, 2006, at 11:29 PM, Andrew Pantyukhin wrote:

> Hi. I have to teach no-frills freebsd courses. I wonder how
> I can arrange all the students seeing on their displays what
> I'm typing in my xterm in real-time. I haven't been very
> successful with xwatchwin (I've been able to see it in action
> but it wasn't very pleasant, and it dumps core on me lately).
> watch(1) seems to be ideal for my purposes - students log
> on to my box (maybe even gain root privileges if I don't
> tweak devfs) and watch my pty. They can even copy and
> paste what I'm typing in their xterms. But there's a show-
> stopper: it seems that only one snp(4) device can attach to
> a tty at the same time and only one watch(1) can use a
> snp(4) at the same time.
> So what do you suggest?
> Hmm... Just as I was typing this I saw a simple solution. I
> can use script(1) dumping to a file with -t0 (flush on every
> char) and people can just tail -f this file. Performance is
> great on a local machine, but is very laggy over NFS... I
> tried 'mount -o acregmin=0,acregmax=0' and the
> perfomance is almost real-time now.
> Great :-) It really is true that many solutions come just as
> soon as you try to describe your problem clearly :-)

Another potential solution is to use VNC - assuming your students  
have graphical displays. I'm pretty sure that multiple VNC viewers  
(clients) can connect to one VNC server, in watch-only mode.


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