Always getting command not found

I'm using Terminal in MAC OS X, and new to this.

I don't know what happened to the path. I always get "command not found".

For example, this is some of what I get:

-bash: ls: command not found

-bash: touch: command not found

What should I do to return the terminal to normal?

Thanks.

---------- Post updated at 09:47 AM ---------- Previous update was at 08:21 AM ----------

I got it solved using this command:

export PATH="/bin:/sbin:/usr/bin:/usr/sbin"

The source I found the solution from was: Unix FAQ (for OS X)