Are you trying to learn *nix, only to have those darn DOS commands pop out of your fingertips instead of the right ones? There's hope for you!

If you decide to run a certain shell (most likely csh, or c-shell), you have the option of mapping all of those DOS commands to the Unix/Linux commands you're yearning to use. This command is called alias, and it works thusly:

alias DOS 'UNIX'
Wherein alias is the command that allows you to make a new name for UNIX commands; DOS is the name of the DOS command you keep typing by accident, and 'UNIX' is the command you meant to type in the first place. For example:

alias dir 'ls -a'
Wherein whenever you accidently type in the DOS command dir by mistake, *nix will automagically replace it with ls -a. Note that since there is a space between the ls and the -a, you use a single quote to show the shell that it is one command with associated switches.

You can set these up in your csh environmental variables so they're always there.