I found a tar.nlm on NW 6.5.7 and I am apparently too stupid to figure out how to use it to take an existing file and zip/tar it up

I accidentally used the tar -c -f sys:\blah\file
and it deleted that file and created an empty .tar file instead


So what I wanted to do was take:
sys:\blah\file and create sys:\blah\file.tar

Any help?