Date:         Wed, 7 Jun 2000 06:31:19 -0400
Reply-To:     Donald Trevoy <d.trevoy@computer.org>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Donald Trevoy <donaldtrevoy@SNIP.NET>
Subject:      Aggregate Storage/Directory Search under UNIX
Content-Type: text/plain; charset="iso-8859-1"

I've been asked to move a library of SAS/Graph macros from OpenVMS 6.2 to
SunOS 5.6; both systems are running SAS 6.12 TS060.  What I'm struggling
with is how to re-create a aggregate storage location on the new platform
that references multiple directories and searches them in order.

The original system uses OpenVMS logicals, one for each of the macros
callable by the users, to define an aggregate storage location in which we
store the code that macro requires.  This we do in a .COM file executed
prior to invoking SAS.  In that file you would find code like this:

$  DEFINE    MACRO_A     LIB:[GRAPHICS.MODULES.MACRO_A],

LIB:[GRAPHICS.MODULES.UTILITIES]

$  DEFINE    MACRO_B    LIB:[GRAPHICS.MODULES.MACRO_B],-

LIB:[GRAPHICS.MODULES.UTILITIES]

$  DEFINE    MACRO_C    LIB:[GRAPHICS.MODULES.MACRO_C],-

LIB:[GRAPHICS.MODULES.UTILITIES]


These macros are modular by design and in these two directories we store the
macro-invoked modules (macros as well) that the user-invoked macro requires.
This code is made available with a series of %INCLUDEs located in the
user-invoked macro.  This code uses the OpenVMS logical as an aggregate
storage location. Within macro MACRO_A, for example, you will find code that
looks like this:

 %INCLUDE MACRO_A(MACRO_1);
 %INCLUDE MACRO_A(MACRO_2);
 %INCLUDE MACRO_A(MACRO_3);

In the first of the directories defined by the logical - the one that bears
the name of the user-called macro (MACRO_A, MACRO_B.) -- we store code used
only by the named macro.  In the second directory (UTILITIES) we store the
code that is shared by multiple macros.

In order to find macro MACRO_1, SAS initially searches the first directory
defined by logical MACRO_A - LIB:[GRAPHICS.MODULES.MACRO_A].  If macro
MACRO_1 is not there, SAS then looks in the second listed location -
LIB:[GRAPHICS.MODULES.UTILTIES].

This technique allows us to eliminate the storage of duplicate code, even
code used by all twelve of the user-callable macros.  It also makes this
code readily available for browsing from the SAS Display Manager.  Because
we used operating system logicals, this code is accessible with OpenVMS
editors such as EDT and EVE as well.

We'd like to preserve as much of this functionality as possible in the new
environment.  In an effort to minimize the cost of re-validating the
software, we'd also strongly prefer to leave the SAS code unchanged,
confining any necessary modifications to the operating specific 'wrapper'
that creates the environment in which they work.

My UNIX guru tells me I can't duplicate this aggregate storage/directory
search technique on the new platform.  Any informed second opinions would be
greatly appreciated.

Once again, many thanks to all!

Don