[TUHS] Control-T (was top)

arnold at skeeve.com arnold at skeeve.com
Wed May 30 19:06:21 AEST 2018

There was a patch floating around circa 1984 that did Control-T
as a mini-ps inside the kernel. We put it into our Vax running
4.2 at Georgia Tech and then later I put it into the Vaxen
I ran at the Emory U. Computing Center running 4.3 + NFS fromm
Mt. Xinu.

It was a cute thing to have.  One of the faculty at Georgia Tech
who had come from MIT saw it and was totally surprised it was
in Unix. :-)

Lord only knows where we got it from. Probably Unix Wizards
or something ...


Norman Wilson <norman at oclsc.org> wrote:

> Back in 1980 or 1981, when I first started hacking
> on UNIX but still had some TOPS-10 DNA lingering in
> my blood, I put in a really simple control-T
> implementation.  Control-T became a new signal-
> generating character in the tty driver; it sent
> signal 16.  Unlike interrupt and quit, it did not
> flush input or output buffers.  Unlike any other
> signal, SIG_DFL caused the signal to be silently
> ignored.  (I don't remember why I didn't just teach
> /etc/init and login to set that signal to SIG_IGN
> by default; maybe I looked and found too many other
> programs that monkeyed with every signal, maybe I
> just didn't think of it.)
> I then wrote a little program meant to be run in the
> background from .profile, that dug around in /dev/kmem,
> figured out what was likely nearest-to-foreground process
> associated with the same terminal, and printed a little
> status info for that process.
> It didn't take long for the remaining TOPS-10 DNA to
> leach away, and besides it is much easier to run some
> program in another window now that that is almost always
> possible, so I don't miss it.  But I like that idea
> better than, in effect, hacking a mini-ps into the kernel,
> even though the kernel doesn't have to do as much work
> to get the data.
> I also thought it made more sense to have a general
> mechanism that could be used for other things.  That
> even happened once.  The systems I ran were used, among
> other things, for developing SMP, the symbolic-manipulation
> interpreter worked on by Stephen Wolfram, Geoffrey Fox,
> Chris Cole, and a host of graduate and undergraduate students.
> (My memory of who deserves credit differs somewhat from
> that of at least one person named.)  SMP, by its nature,
> sometimes had to spend a substantial time sitting and
> computing.  Someone (probably Wolfram, says my aging
> memory) heard about the control-T stuff, asked me how
> to use it, and added code to SMP so that during a long
> computation control-T would tell you something about
> what it was doing and how it was progressing.
> Since the signal was, like interrupt and kill, sent
> to the whole process group, there was no conflict if
> you also had my little control-T monitor running in
> the background.
> I never tried to send my hacked-up UNIX to anyone else,
> so if anyone else did the same sort of control-T hack,
> they likely invented it independently.
> Norman Wilson
> Toronto ON

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