The unp script for Linux is a script that will detect what the archive is and call the appropriate program to handle it. This is a very useful script for the command line user. In the example below I am unpacking a zip file.
jason@eyjafjallajkull:~/Downloads$ unp northwind.sql_.zip Archive: northwind.sql_.zip inflating: northwind.sql
if the required programs are not installed, you will get this helpful error. This will tell you which packages to install to proceed.
jason@eyjafjallajkull:~/Downloads$ unp fallujah1_2.7z Error, following packages must be installed in order to proceed: p7zip or p7zip-full
But, this is a very powerful script and well worth installing to take care of any strange archive format that you encounter on the Internet.
sudo apt-get install unp to install this useful script.