Has anyone implemented Variant Links on Suns?

[Dan Smith]

	[Skip the first part if you are already familiar with VL's]

I really enjoy using Suns, and recently started using an Apollo as well
for a project.  One thing that I like in their setup is Variant Links.  In
a nutshell, the value of an environment variable is used to help resolve a
symbolic link.  They have something like:

	usr ---> $(SYSTYPE)/usr

so that if $SYSTYPE is "4.3bsd", you get /4.3bsd/usr, and if it is
"5.3sysv", you get /5.3sysv/usr.  If $SYSTYPE is undefined you end up
going nowhere.

	[end of first part...]

I see where variant links would come in handy for allowing several
versions of software to coexist in the "same" place.  Specifically, I
would love to be able to put X11R3, R3 with Motif, and R4 in the "same"
place, a la:

	/usr/include/X11  -->  $(XVERSION)/include/X11		or
			--> /usr/include/$(XVERSION)

That way users would just have an environment variable pointing to what
they need, and everyone could still go on speaking of "/usr/include/X11"
in a generic sense.  There are so many applications for this!  I think
that if the env var is not set, then you should end up at (literal)
$(FOO)/whatever, in order to be compatible with some application/user that
put "$(" in their filenames (beats me why anyone would do that. but then
again...)

I think this would have to be done at the kernel level, in order to be
transparent to applications.  I'm guessing it would be a small change to
whatever looks up symbolic links (look for a $(VAR) element, resolve it,
and insert it into the pathname).

Wish I had the source (nope, I'm not an adb hack!)...  Anyone ever do
this?  (Donning an asbestos overcoat :-)

				dan

   dansmith at well.sf.ca.us   daniel at island.uu.net   unicom!daniel at pacbell.com
ph: (415) 332 3278 (h), 491 1000 (w) disclaimer: Island's coffee was laced :-)