The Rutgers version of READ20 can handle retrieve requests from a
DEC-20 archive tape.  This is not documented in the man page, because
it is a very specialized function that is unlikely to work outside
Rutgers.  Users issue retrieve commands via the program "retrieve".
This program assumes that users have a file .20-archive-dir in the
directory containing information needed to form the retrieve request.
The DEC-20 archive system operates in terms of save set and file
numbers.  Thus in order to retrieve a file, you must know those
numbers for it.  Normally, this information is stored in the FDB of
the file on the DEC-20.  For this scheme to work on Unix, we have this
information.  The file .20-archive-dir is in the following format:


ADVENTURE.PAS.1,0,29-May-84 18:51:31  GG11A   8,,1  GG11B   7,,1
ADVTYPES.PAS.1,0,29-May-84 18:43:22  GG11A   8,,2  GG11B   7,,2
AID.EXAM-SHIFTS.1,0, 7-Dec-84 03:05:00  GG18A   13,,1  GG18B   12,,1
filename         size  date             tape    set,,file ...

