Date: Mon, 3 Apr 95 10:54:43 MDT From: terry@cs.weber.edu (Terry Lambert) To: chaos@rivers.oscs.montana.edu (Jason Boerner) Cc: freebsd-questions@FreeBSD.org Subject: Re: Virtual displays on a dumb terminal over ttyd0??? Message-ID: <9504031654.AA06969@cs.weber.edu> In-Reply-To: <Pine.ULT.3.91.950401225522.19463B-100000@rivers.oscs.montana.edu> from "Jason Boerner" at Apr 1, 95 10:58:32 pm
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> Is there a way to force a dumb terminal (A vt300) over ttyd0 to have > virtual displays in the same fashion that the console terminal in > character mode has???? Yes. The VT300 series has multiple pages of memory and the idea of "switch session" (it has a key for it). It assumes intelligence on the part of the other end to implement the protocol, however. Generally, all DECServer terminal servers do the implementation for it. You should use a line analyzer to dump the traffic; I don't remember the undocumented escape sequences they used to do the job. You should note that the protocol on switching sessions this way is largely similar to transparent printing; that is, there are some assumptions about interruption of escape sequences. Typically, this will mean that you will either need to ensure your I/O is done by the host machine in such a way that writes of escape sequences are atomic (VMS guarantees this, for instance), *OR* you will need to maintain a finite state automaton that knows what state the terminal is in and only allows session switching at state 0 (no escape sequence in progress). Maintaining a finite state automaton for the terminal for transparent printing is actually one of the technology pieces that makes to Digiboard driver available only under non-disclosure. They were one of the first companies to do this. > Along the same lines; Is there a way to force a log-out of a terminal > that has been inactive for x amount. of time? Not really along the same lines at all. 8-). Look in the comp.sources.unix archives; there are bazillions of these programs. Several of them are named "watchdog". You could do the same thing relatively easily, depending on what you mean by "idle" by simply statting the tty to determine last access time (ie: look at how "who" and "finger" count idle time). Terry Lambert terry@cs.weber.edu --- Any opinions in this posting are my own and not those of my present or previous employers.
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