mj@myrias.UUCP (Michal Jaegermann) (10/20/88)
(Whatever is described below was checked for a gulam version
which identifies itself as:
beta test version 1.03.04.05 121887 of
yet another shell for AtariST/TOS
Your mileage may vary!!)
As you may not know, a very popular Gulam shell (many thanks to
Prabhaker Mateti and Jwahar R. Bammi). includes quite powerful facility
to invoke gulam services from a program started from gulam. In contrast
to many others shells floating aroung this is not done by executing
the next incarnation of gulam. Instead there are provided two pointers
which provide execution 'hooks' for all gulam commands. A bright sight
is that this approach does not take any extra memory and a start-up
time is negligible. A dark side is that documentation describing this
facility is either misleading or plainly wrong. (As an aside - this
is, alas, not the only place in documentation requiring touch-up.
For this version, gulam.hlp, for example, does not correspond very well
tp reality).
This note is a kind of erratum, which, hopefuly, will help to clarify
an ensuing confusion, which seems to be quite widespread.
When you are running Gulam a TOS variable '_shell_p', at 0x4f6,
contains an address of a location named 'togu_', which is the last entry
in a 16 byte long table. The format of the table is (this is mostly quoted
from the documentation):
.long 0x86420135 / our magic number (4 bytes)
jmp getlineviaue_ / 0x4ef9,address (6 bytes)
togu_: jmp callgulam_ / 0x4ef9,address (6 bytes)
It clearly follows from that that magic number is located 10 bytes before
'togu_' and not, the documentation suggested, 12. What's more, the magic
number should be equal *(long *)(*(char **)0x4f6 - 10), instead of a
given *((long *)0x46fL - 12L), which will produce a value from an address
way off. On the top of it, an actual magic number in my copy of Gulam
is not like the documented but it equals 0x00420135. Use Gulam 'peekw'
to check what you got. To be on a safe side, until the matter
is fully clarified, I am using only a lower half of the magic number,
which seems to be correct; i.e. short_magic = *(short *)(*(char **)0x4f6-8).
Two other items in the table are entry points to two functions
'getlineviaue' and 'callgulam'. The information given in the documentation
about them is mostly correct, with a similar mix-up in a calculation
of an address of entry to 'getlineviaue', like the one described above.
Also, strictly speaking, 'getlinevalue' does not return anything, since
it is declared as 'void'. As a side effect it modifies a contents of
a user supplied buffer, copying there a contents of a command line. It
would be probably more convenient if, instead of being void, it would return
something useful, say a number of copied characters, but it doesn't,
so we may have to live with that. Just to make our life more
interesting, the other function, 'callgulam', returns 'int' - the return
status of an executed command. This makes wonders to types of your
pointers. See the supplied program example for to see how to cast.
All of this to ensure that your C-compiler will not get totally lost.
If you have a compiler which accepts the stuff in a form from an original
docs - replace your compiler. Fast!
(As an aside - all this pointer play would be easier in assembler,
if you feel so inclined).
While experimenting whith the program example try the following.
Call 'ue' on some file, position cursor somewher down the text and
stop editor with ^Z. Try some other commands and upon return to Gulam
type 'fg'. Repeat experiment stopping the editor in Gulam and typing
'fg' from the demo program prompt. Don't you think that this is a nice
way to run editor for your, say, Lisp interpreter?
Some things are still missing. One cannot tell 'ue', on a command
line, to load a file and go to the line 247. Or there is a way and I
am simply not aware of it? And I know of no way to grab a result of
a command, stuff it into a variable and use it for a test of conditional
script execution. Oh well, maybe in some future release...
Two other, non-interactive, ways of calling Gulam are also mentioned
in docs. I did not try 'Pexec method', but attempts to execute
gulam as a program with arguments, as described, produced only
nonsensical error messages about 'invalid regexp' and error number -33.
Can anybody shed some light on that matter?
Michal Jaegermann
Myrias Research Corporation
Edmonton, Alberta, CANADA
...alberta!myrias!mj
(or you may try mj@myrias.UUCP)
------------------------------------------------------------------------------
/*
* A demo program to show a usage of Gulam 'hooks' - call from
* Gulam shell! When asked, try different gulam commands, ue
* in particular.
*
* A numbers of pointers floating around is a little bit higher
* than necessary, but we will waiste some memore for the sake
* of clarity.
*
* Michal Jaegermann, October 1988
*/
#include <stdio.h>
#include <osbind.h>
#include <string.h>
#define SHELLP ((char **) 0x04f6L)
#define G_MAGIC 0x0135
main()
{
long save_ssp;
short sh_magic;
char buf[258];
char *tgptr; /* storage for togu_ */
/* if you really would like to have it right, then */
/* tgptr should be a pointer to void - */
/* a bit of overkill on ST :-) */
int (* cgp)(); /* pointer to callgulam() */
/* also contains togu_, but */
/* a type is different */
void (* glp)(); /* pointer to getlineviaue() */
fprintf(stderr, "Welcome to callgulam demo.\n");
save_ssp = Super(0L);
tgptr = *SHELLP;
Super(save_ssp);
if (G_MAGIC != (sh_magic = *((short *)(tgptr - 8)))) {
fprintf (stderr, "wrong magic value %x\n", sh_magic);
exit (1);
}
cgp = *((int (*)()) tgptr);
glp = *((void (*)()) (tgptr - 6));
(* cgp)("echo 'test of Gulam'");
(* cgp)("echo 'executing ls -l'");
(* cgp)("ls -l");
(* cgp)("echo '-----------------'");
(* cgp)("ls -R -t a:\\ ");
(* cgp)("echo ' '");
(* cgp)("echo ' '");
(* cgp)("set tmp_old_prompt $prompt");
(* cgp)("set prompt 'At your service, Sir!'");
/* change a gender if a need will arise */
(* cgp)("echo 'Awaiting your commands!!'");
/* the following loop will cycle until it will get an empty line */
while ((* glp)(buf), putchar('\n'), 0 != strlen(buf)) {
/* the new line not supplied */
/* by Gulam - DIY, mate */
(* cgp)(buf);
}
(* cgp)("set prompt $tmp_old_prompt");
(* cgp)("unset tmp_old_prompt");
fprintf (stderr,"\nNice talking to you, see you later.\n");
exit(0);
}
/* -----------------/ that is all for today /--------------------- */
--
Michal Jaegermann
Myrias Research Corporation
Edmonton, Alberta, CANADA
...{ihnp4, ubc-vision}!elberta!myrias!mjggf@js.UUCP (Gary Frederick) (10/21/88)
There are several versions of gulam floating around. Some of them
have 'problems' passing parameters to programs. Enter the following
from inside gulam to find if you are using one of the versions in
question:
:gulam.prg -c ls
If another gulam runs and you get a 'ls' directory listing, you got
one of the older gulams that passes parameters to programs.
I am entering this reply with our rn program. It pexecs gulam and
passing it the command line '-c ue article.old article.new.'. The
version of gulam that will take the command line is
beta test version 1.00.00.02 110287
We have used the _shell_p TOS variable with gulam to test the two
entry points. They work. I do not have the source of the tests to ul
:-). We were using V 1.03.04.04. I will look for the demo in my
spare time (* spare time??? *)
We also updated the gulam.hlp file to added error messages. That
version of gulam is
beta test version 1.03.04.04 121387
with a notice of changes by ggf@jsbbs. That version will take error
files from Jefferson Software's compiler and go from line to line in
the source file. It works with MWC error messages, but complains
about the lack of an EOL on the last line on messages generated by
redirecting the error messages.
We plan on getting in touch with pm and bammi soon (* real soon?
see comment above on time *) to see what the latest version is.
And to get the (* hope hope!!!! *) minix version. (* if there is one *)
(* and with zmodem built in *) (* and with the ability to edit the te
buffer *) (* and and and ... *)
Gary (* responsible for my actions *) Frederick
UUCP: ggf@js.UUCP
uunet!noao!asuvax!nud!js!ggf
BIX: ggf
STadel: jsbbs (602) 276-6102