>     "gzcat filename | (cd / ; tar --unlink -xvfp -)"
> 
> fails. The output is:
> 
>     "tar: can't open p: No such file or directory."

Try

    gzcat filename | (cd / ; tar --unlink -x -p -v -f -)

The option f must be followed by the filename (- in this case).

  -jm