This problem builds significantly on the previous problem. Specifically, it asks you to again use

fork() to create processes and exec() (or one of the many variants) to assign the newly created

processes what to do. In addition, however, it asks you to mimic the behavior of a shell command

such as:

ls | wc

What happens in the case above is the output of the first command (ls) becomes the input

to the second command (wc). (Try it in a terminal on a Unix machine).

Thus, you are required to write another program that:

Expects an input of the form: cmd1 | cmd2

Creates two processes

Makes the first process run cmd1

Makes the second process run cmd2

Makes sure that the output of the first process becomes the input of the second process (using

the function pipe()).

Waits for the two processes to finish before it ends by printing ++++ on a new line.