一个简单的shell命令解释器，有重定向，管道，历史等功能。-A simple shell command interpreter, redirection, pipes, history.

 Your shell prompt MUST adhere to the following format: o Current date (optional) and time (mandatory) followed by the hash sign (e.g., 13:03:00#)  Your shell MUST support, at minimum, the following commands: o The internal shell co