0x16. C - Simple Shell

TASK :

---------mandatory--------

0. Betty would be proud
1. Simple shell 0.1
2. Simple shell 0.2
3. Simple shell 0.3
4. Simple shell 0.4
5. Simple shell 1.0

---------advanced-------

6. Simple shell 0.1.1
7. Simple shell 0.2.1
8. Simple shell 0.4.1
9. setenv, unsetenv
10. cd
11. ;
12. && and ||
13. alias
14. Variables
15. Comments
16. File as input