From:	CSBVAX::MRGATE!info-vax-request@kl.sri.com@SMTP  3-APR-1988 12:15
To:	ARISIA::EVERHART
Subj:	Re: Chaining images... THE source


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Date: 28 Mar 88 02:17:22 GMT
From: garry@tcgould.tn.cornell.edu  (Garry Wiegand)
Organization: Cornell Engineering && Ithaca Software, Inc.
Subject: Re: Chaining images... THE source
Message-Id: <4202@batcomputer.tn.cornell.edu>
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In a recent article carl@CITHEX.CALTECH.EDU (Carl J Lydick) wrote:
>I'm one of the people who referred you to LIB$FIND_IMAGE_SYMBOL.  Let me point
>out  again  that  this  works only with SHAREABLE images.  This means that you
>can't chain most images that are linked to be run via a command from  the  DCL
>level...

Now, if you want to be a real wiz, what you do is:

A) get your DCL command line from wherever and nibble off the command verb.
   Either use a hard lookup table (ie, "DELE" -> SYS$SYSTEM:DELETE) or
   a program like Verb as a subroutine to find the right image to 
   activate.
B) Activate that image with SYS$IMGACT - it doesn't have to be a shareable
   image.
C) call Find_Image_Symbol on DCLTABLES.EXE to get the address of the real
   DCL tables (the name I forget, use ANAL/IMAGE to see it) (the tables are 
   up in P1 space too, I think, if you prefer)
D) Tell CLI to parse up the command line please
E) Call the entry point of DELETE, DIRECTORY, or whoever the image turned 
   out to be *as a subroutine*. It don't know/can't tell that it isn't 
   running as a normal DCL call, calls CLI like usual, and everything works
   out.

I leave trapping out possible SYS$EXIT calls from the called program as an 
exercise for the reader.


I used to have the code for this and a bunch of other nonsense 3-4 years,
but I just looked around in all the dusty places and don't see it 
anymore.  ((Before we got involved in graphics, we were playing some
ideas for some new VMS utilities. I got involved in the above in the 
course of adding an some new switches/abilities to existing VMS commands -
I could have just duplicated the previous VMS functionality and gone
on, but that was tedious and I also didn't want to have to *keep* 
duplicating DEC's functionality. So we just used Dec's programs as 
subroutines of our own.))

Oh, the functionality involved was an "UNDELETE" command, with related
switches DIR/DELETED, DELETE/REALLY, etc etc etc. All blended in
nicely. Cute. (Normal-delete became a surreptious Rename to an invisible
parallel directory tree.)

Never did get around to trying to sell the various things - people still
are just barely interested in non-Dec *hardware* - VMS add-on software 
was/is an even tougher row to hoe.

garry wiegand   (garry@oak.cadif.cornell.edu - ARPA)
		(garry@crnlthry - BITNET)