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From: SCHOMAKE@HNYKUN53.BITNET (Lambert Schomaker)
Newsgroups: comp.os.vms
Subject: Re: (spawn .COM): setting logicals and symbols from within an image
Message-ID: <8705222324.AA00343@ucbvax.Berkeley.EDU>
Date: Fri, 22-May-87 09:00:00 EDT
Article-I.D.: ucbvax.8705222324.AA00343
Posted: Fri May 22 09:00:00 1987
Date-Received: Sat, 23-May-87 17:36:21 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 26

BOB <SLOANE%UKANVAX.BITNET@WISCVM.WISC.EDU> writes:
> ...LIB$SPAWN appears to create a new process, and any
> commands/logicals/symbols defined go away when the .COM file terminates.

The solution to your problem is in the RTL routines LIB$SET_SYMBOL and
LIB$SET_LOGICAL (see RTL Ref. manual) so you won't have to make a .COM
file and spawn it.

Note: Symbols (global or local) are inherited and not
pushed back to ancestor processes when created or changed.
Logicals in the /JOB table, however, are globally accessible
by all subprocesses in the process tree, e.g.:

$ DEFINE/JOB BLACKBOARD "hi children!"

This is the easiest way to send messages to subprocesses in VMS.
Just hibernate the subprocess and let it translate some /JOB
logical on wake-up to let it decide what it has to do.

                 *
               ^^^^^
      KKKKKUUUUNNNNN
      KKK  UUUU NNNN           Lambert Schomaker
      K    UUUU  NNN           SCHOMAKE@HNYKUN53.BITNET
      KKK  UUUU   NN           Nijmegen, The Netherlands.
      KKKKK UU     N