SUMMARY: "Virtually add" Dir 1 to Dir 2?

From: Jochen Bern (bern@kleopatra.Uni-Trier.DE)
Date: Fri Oct 01 1993 - 16:10:51 CDT

This is a *real* fast one this Time. Yesterday, I asked:

> To make Things short, I would like the Shell or something relative-
> ly "close" to it to virtually add the public Files from the corres-
> ponding public Directory whenever a User looks up his private Di-
> rectory, including any open-for-read. On VMS, this would be as sim-
> ple as defining a Logical with several Translations and using it in
> the Path. I seem to remember that there is something similar for
> Unix, but I can't remember the Name for the Life of me! And a Scan
> in the Latech Archive turned up nothing.
> This is for 4.1.2 (on sun4c's), and the Software which has to deal
> with this Stuff is partly C, partly csh Script; I could convert the
> latter to C quite easily, if necessary.

Seems I didn't make clear what I wanted. I thought of something like this:

user% cd ~/sub
user% ls
user% ls ~main/sub
user% cat ~main/sub/file2
   Old Stuff
user% # Do Magic
user% ls ~main/sub
user% ls
   file1 file2
user% cat file2
   Old Stuff
user% cat - > file3
   New Stuff
user% cp file3 file2
user% cat file2
   New Stuff
user% ls ~main/sub
user% cat ~main/sub/file2
   Old Stuff

The $ 1,000,000 Answer (and the Thing which haunted my Memory) is:


which is Part of SunOS 4.x. Thanks to, (Louis M. Brune), David Fetrow
<>, (Steve_Kilbane),
Mike Raffety <>.

Only Drawback: The Magic occurs where the low-Prio Dir used to be (~main/sub
in the Example above), not over ~user/sub, but I can counter this with TFS's
Capability to do more than 2 Levels; I'll overlay the real private Dir over
the public Dir over a Dummy private Dir.

Other Ideas:

Anthony Baxter <>: Use Prospero, it's a Package for virtual
FSes. (I'll have a Look at it, thanks.) (Sumner Hushing), David Fetrow
<>: Use symbolic Links. (Sorry, that's
not it!) (Louis M. Brune): Apart from TFS, you might write your own
open() Replacement. (Yes, but it's for the C Programs only.) Automounter does this. (I didn't check this out.) (Steve_Kilbane) noted that SUN might drop TFS in the
Future; Another Reason for me NOT to go Solaris!

Thanks to you all,
                                                                        J. Bern

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