> Many thanks to all the people who have 
> replied to my query.

You have a nice list.  Now for some practice, you can get a free Unix shell
account on several systems.  Check out the resources at these links
maintained at the Open Directory Project:

http://dmoz.org/Computers/Internet/Access_Providers/Unix_Shell_Providers/Fre
e_Shells/

John Tobler
grepninja / diganet.com