cpio

[karish]

In article <625 at mccc.UUCP> pjh at mccc.UUCP (Peter J. Holsberg) writes:
>
>Do cpio and ctccpio always overwrite anything that is already on the
>diskette or tape?  If so, is there any 'copy' program that does not?
>Thanks.

cpio only overwrites what's on a tape if you tell it to.  If you
use a no-rewind tape special device, and space to the end of the
previous file first, you can write a second file onto the tape
after the first one.  On BSD systems, the `mt' utility lets you
reposition the tape.  The comparable AIX command is `tctl'.  I
don't know whether this is a standard SysV command.  Of course,
you have to remember that there are two files on the tape when you
extract data.

It's harder to do this on diskettes.  Piping cpio to dd might do
the trick, if you specify one of the `skip' options to dd.

The tar command will append to an archive, if you use the 'r' flag.  
This is usable for incremental backups.  The disadvantage is
that it's impossible to extract earlier versions of files from the
archive; the tape is read in order, and later versions overwrite
earlier ones on extraction.

Chuck Karish		ARPA:	karish at denali.stanford.edu
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