This is a basic shell implementation on minix3.3.0

the goal is to understand how a shell works and know some of the basic system calls.

1. Build: using "clang shell.c -o shell" to compile
2. Run: "./shell"
3. Features: my program implements all the requirements in the assignment's details from 1~7 and the 'cd' command.
4. Notice: pipe only support single pipe. It cannot support multiple pipes or a combination of pipes and redirection in one command.
5. Testing:
   • You can see '>> ' if my shell is running, type any commands you want. Here are some examples:
   • ls
   • clear
   • ls -l
   • cd /root
   • cd ..
   • ls -l &
   • ls -l > foo
   • sort < foo
   • ls -l | more
   • poweroff