To unpack a standard .tar file, use the command

tar -xvf filename

The Command options of tar:

* x: decompress something
* t: view contents
* v: verbose mode
* f: input from a file

…some versions of tar support inbuilt decompression of gzipped tar files. This requires the z option, transforming the command to:

tar -xvzf filename

To create a tarball, you can use

tar cf tarballname.tar files

If you just want to view the contents of a tar file instead of extracting it:

tar -tf filename

You can filter it through gzip or bunzip2 respectively:

tar -tzf filename
tar -tjf filename

[http://wiki.linuxquestions.org/wiki/Tar] [http://unixhelp.ed.ac.uk/CGI/man-cgi?tar]