untar only newer files (updating SunOs without wiping out disk)

[Stephen R. van den Berg]

I'm trying to update SunOs to 4.1.1 by simply untaring everything on top
of the old things.  So far things are going fine, and I managed to update
all executables (including the dynamically linked libraries) while keeping
the system running (multiuser).

There are a few sensitive files in /etc and some other obscure places that
I have modified from the original distribution (of the old SunOs).

Now I want to restore certain tapes, but I want to make sure that
only newer files will be extracted.  That is, files like /etc/passwd
should *not* be overwritten.

Now, is there an obvious way to accomplish this?  I have ploughed through
the manuals and man pages to no avail.

Thanks.
--
Sincerely,                 berg at marvin.e17.physik.tu-muenchen.de
           Stephen R. van den Berg.
"I code it in 5 min, optimize it in 90 min, because it's so well optimized:
it runs in only 5 min.  Actually, most of the time I optimize programs."