Not trying to be a jerk... It sounds to me like it's a programming assignment. I ran across at least one class in college that assigned a program description such as:
Write a basic command interpreter.
The program should present the user with an opportunity to enter commands, process them, and wait for the next command.
Your program will need to parse the command line to determine the command and argument(s).
The commands that must be supported are:
So, there are three things I see that will prevent anyone from posting a "solution". First, it sounds like homework.
Second, nobody is receptive to "I can't do it, so do it for me" requests. If you want help, the traditional approach is to post the code you have, explain what's not working, and identify what's been tried to fix it.
Lastly, the foundation of any shell is simply a loop: read input from the user, parse, take appropriate action, get input from the user. It's not tough. That's not to say bash is simple, but it follows the same premise. The OP can always download the source code to bash and snoop around if ideas are needed.