## Exercise 1

 1. Write a C program that creates 2 pipes.
 2. Then it forks off 2 child processes.
 3. Sends each of them a ‹hello› through the pipe.
 4. The children both print their pid and the message.

Now let's learn about ‹dup› and ‹dup2›, so that we can replicate
what shell does when we use ‹|›, but in C. That is, we will use
‹pipe›, ‹fork› and ‹exec› together. See ‹dup.c›.
