Develop a shell program

shell program requirements: 1) launch programs with any number of arguements (exec the arguement function eventually) 2) support input/output redirection a- >fn (redirect stdout to fn) b- < fn (redirect stdin to fn) c- >>fn (redirect stdout to fn in append mode) 3) support piping (cmd1 | cmd2) (atleast 2 processes, better if support any number of processes) a-note: all processes in pipe should be in same process group. 4) built-ins a- cd b- exit c-set 5) support variable expansion