The following is a series of conversations that took place
on the subject of ZCPR3 Shells, a powerful UNIX-like utility
that seems much under-utilized. These messages were taken
from the Ladera Z-Node using the ZCPR3 RECORD function.
Date: 15 Feb 86 18:55:16 PST
From: JOHN POPLETT
To: AL HAWLEY
Re: SHELL GAMES
Al,
I recently fooled with a program called LUP.PAS (a Turbo-
Pascal version of LUX) that seemed to me to have the right idea
in that it uses existing RCP/M utilities (LDIR, TYPEL, XMODEM/
KMD) to do its job. It doesn't require it's own versions of
these programs and that amounts to a considerably saving in cod
e size. LUP.PAS uses the command line buffer to create its
"menu" effects. But wouldn't this work more effectively as a
shell? And in any case, how do I begin writing programs that
take advantage of these sort of goodies. ZCPR3, I can see,
presents a ripe opportunity to eliminate a lot of redundancy.
What files do you recommend that I get to further my efforts?
I'd like to be able to stick to 'C' and to MAC if possible.
What do you recommend?
John Poplett (PPR MBBS)
Date: 18 Feb 86 12:46:15 PST
From: FRED HAINES
To: JOHN POPLETT
Re: Z3 shells
John,
I'm not quite sure what you are loking for from your
message, but, if you're willing to run your program under
the ZCPR3 OS, you can designate any *.COM file whatever as
a shell with the Z utility SHSET. What this does, essentially,
is, when you leave program A, which you've designated as
your shell, to run program B, the minute you finish with B,
A will reload automatically. Beyond this, you can nest shells
to several levels, and you can pass variables from one shell to
another with SHVAR. One of the glories of the Z environment is
a fabulous flexibility to maintain and manipulate shells, and I
doubt whether any of us have even begun to explore the vast
range of possibilities of this.
If you're thinking about doing it in MS-DOS, I don't really
know how you'd go about it, but you might be able to write a
program that creates a shell stack, which is the feature of Z
that makes all this possible. You would want to set it up more
or less like any normal stack, except - if I'm not mistaken -
you would want to store not addresses in it, but the actual
name of the program. I guess that means storing the name
upside down, pushing the last letter first, so when you popped
the shell stack it would come out in the right order. It would
have to be a very complicated program though....
Date: 22 Feb 86 18:38:44 PST
From: SYSOP
To: JOHN POPLETT
Re: CHAINING/Z3 CMD BUF
The documentation and code for chaining to another command on
exit from BYE is contained in the file BYEMOD.LBR in the
MODEM directory. It describes the modification to BYE, and
contains a listing of the alias BYE chains to in my system.
I'll try to u/l the file to you. The principle used is
applicable to other programs as well, although the facilities
of ZCPR3 are usually adequate to accomplish successive
execution of programs without this kind of modification. The
factor that makes this technique important with BYE is that
BYE effectively 'cleans up' ZCPR3 buffers before exit in the
cause of system integrity. That clean-up interferes with, for
example, invoking BYE as a shell. If you have any questions,
I'll try to answer intelligently..
Date: 26 Feb 86 23:03:14 PST
From: JOHN POPLETT
To: SYSOP
Re: Z3 SHELLS
Al,
I wrote a provisional/experimental Z3shell this evening, a
very simple matter. The prgm checks the shell stack and if no
shell is active installs itself and prints a message to that
effect (i.e. "Shell installed" a la SH.COM). Then, I go to a
endless loop which prints a command line prompt, gets the
command line, stuffs it in the Z3 cmd buffer and executes.
If a control-c is entered from the command line, the shell
uninstalls itself and returns to CP/M. You're BYEMOD code
fragment was a big help. I wrote a 'C' function in ASM with
the fragment as a model. Now here's a question: how do you
think I could leave the shell to execute the Z3 cmd buffer
without a warmboot in between? Right now, I'm playing it
safe and jumping to warmboot at the end of the chain function.
But I'd like to avoid the warmboot if possible. Is there a plac
e in Z3 I can jump to simply to "load and go"???
J. Poplett
P.S.-If you want to see my code, I'll be happy to send it u
