Jerry Pournelle on UNIX (From BYTE)

[Earl Killian]

Conditional symbolic links sound a little strange to me.  How about
instead the following idea from the ancient past:

The ITS operating system had both symbolic links and things called
translations.  Symbolic links were more heavily used, but you could do
cute things with translations, which were essentially per-process
renamings.  The best way to describe ITS translations to the Unix
community would be to say they were a per-process sed script applied
to every filename passed to the kernel.  As such you can modify a
filesystem (from your perspective at least) that you don't have access
to.

This very general facility could replace lots of special-purpose
hacks.  Suppose you wanted to change rm.  Adding an alias, or an rm
command in your path doesn't suffice because some scripts etc. say
/bin/rm.  So you add s|^/bin/rm$|/user/me/bin/rm| to your translation
list.  The csh ~ hack could be done by having s|^~|/user/me|, and then
it wouldn't be limited to csh command lines.  The system V TMPDIR
environment variable would be unnecessary.  Etc. etc.