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From: milne@ics.uci.edu (Alastair Milne)
Newsgroups: comp.lang.pascal
Subject: Re: DOS Environment Variables
Message-ID: <2813A6CD.20250@ics.uci.edu>
Date: 23 Apr 91 03:15:24 GMT
References: <4744@ash54.UUCP> <7333@vice.ICO.TEK.COM>
Distribution: USA
Organization: UC Irvine Department of ICS
Lines: 37

In <7333@vice.ICO.TEK.COM> bobb@vice.ICO.TEK.COM (Bob Beauchaine) writes:

>In article <4744@ash54.UUCP> hamilton@motcid.UUCP (Danial Hamilton) writes:
>>My son programs using Turbo Pascal, and would like to pass
>>a value from his Pascal program to another program via a
>>DOS environment variable.  Can he do this?  Can someone
>>tell him how?  He knows how to set the errorlevel, and could
>>accomplish his goal that way, but it is not as elegant of a 
>>solution as he would like.  Any help out there?

>  The discussion on permanently changing an environment variable
>  was on this group some time ago; sorry, I can't refer you to
>  an article, but perhaps someone else can.  Be warned; the topic
>  is probable more advanced than you think.

  Somebody posted a unit that was supposed to do this safely.
  Unfortunately I missed it :-( :-(.  The trick is to add the
  variable to the environment of both your own program *and* the
  that of the shell that called it -- without at the same time
  corrupting DOS' memory list.  As Bob says, rather an advanced topic.
  
  I must admit I find it ridiculous that proper facilities for passing
  data aren't provided.

>  Another scenario you might consider is using the Dos interprocess
>  communication area.  Any good text on the inner workings of MS-DOS
>  will contain an explanation.  The one I know of is Peter_Norton's_
>  Guide_to_the_IBM_PC.

   This area is about 15 bytes long and, according to Norton, not 
   documented for later DOS releases.  I don't know how one is suppoed
   to use such a miniscule area.  Clearly, it can mostly only be used
   to refer to where the actual data are kept -- but where is that?
   I suspect it goes almost totally unused.


   Alastair Milne