> From: Charles Anthony
> /home/CAnthony
I think it was >user_dir_dir>Group>User, wasn't it? I seem to remember my
homedir on MIT-Multics was >udd>CSR>JNChiappa?
And I wonder if the 'dd' directory on PDP-7 Unix owe anything to 'udd'?
Getting back to the original query, I'm wondering if '/' was picked
as it wasn't shifted, unlike '>'?
Noel
On Mon, 21 Oct 2019, Andrew Hume wrote:
> the gt40??? oh my lord! good job i am en route to the bell labs 50th
> anniversary.
> its been a long time since i heard the name “Dave Horsfall”!
Yep :-) Although now retired, I'm still active in Unix projects.
-- Dave
I was about to add a footnote to history about
how the broad interests and collegiality of
Bell Labs staff made Space Travel work, when
I saw that Ken beat me to telling how he got
help from another Turing Award winner.
> while writing "space travel,"
> i could not get the space ship integration
> around a planet to keep from either gaining or
> losing energy due to floating point errors.
> i asked dick hamming if he could help. after
> a couple hours, he came back with a formula.
> i tried it and it worked perfectly. it was some
> weird simple double integration that self
> corrected for fp round off. as near as i can
> ascertain, the formula was never published
> and no one i have asked (including me) has
> been able to recreate it.
If I remember correctly, the cause of Ken's
difficulty was not roundoff error. It
was discretization error in the integration
formula--probably f(t+dt)=f(t)+f'(t)dt.
Dick saw that the formula did not conserve
energy and found an alternative that did.
All, we had another dozen TUHS suscribers to the list overnight. Welcome.
A reminder that we're here to discuss Unix Heritage, so I'll nudge you
if the conversation goes a bit off-topic.
So I'll kick off another thread. What was your "ahah" moment when you
first saw that Unix was special, especially compared to the systems you'd
previously used?
Mine was: Oh, I can:
+ write a simple script
+ to edit a file on the fly
+ with no temporary files (a la pipes)
+ AND I can change the file suffix and the system won't stop me!
I was using TOPS-20 beforehand.
Cheers, Warren
DMR explained how PDP-7 UNIX was used in "The Evolution of the Unix
Time-sharing System" but having played with it myself, I stumbled in a
couple of cases and found it a bit awkward to use.
Maybe someone (ken and doug?) can shed some light on "elaborate set of
conventions" that dmr mentioned.
My questions are these:
you cannot execute a program if you're in a directory you can't write into.
I asked Warren about this when I first tried pdp7 unix and he
explained it to me: the shell creates a link to the binary and executes
it. If it can't write into the current directory, it fails to create the
link and hence can't execute the program.
How was this handled in practice? did users have write
permissions on all directories? did you just stay in your directory all
the time?
. and ..
Was this introduced first with PDP-11 unix or did the convention
start on the PDP-7 already? It certainly seems to be the case with .
but how about ..? the dd directory seems to take on the role of a sort
of root directory and the now discovered program pd actually creates a
file .. (haven't tried to understand what it does though yet)
What does dd stand for, dotdot? directory directory?
aap
> As noted in the jargon file, the dd(1) syntax is deliberately reminiscent
> of the DD statement in IBM JCL. This was presumably a joke
That is certainly true and reflects its major early usage to
prepare tapes to carry to other systems.
Though I haven't use dit in ages, I recall that the joke was
so fully engtained that the command was more likely to be
written "dd ifile=x ofile=y" than "dd <x >y"
Doug
> From: Abhinav Rajagopalan
> I only now realized that only mknod existed, up until a long time, only
> later on with the GNU coreutils did mkdir as a command come into
> existence.
Huh? See:
https://minnie.tuhs.org//cgi-bin/utree.pl?file=V6/usr/man/man1/mkdir.1
(And probably before that, that was the quickest one to find?)
Maybe that was a typo for 'mkdir as a system call'? (I recall having to do a
fork() to execute 'mkdir', back when.) But 4.2 had mkdir().
Noel
