Lots of processes

1.

Right after the #include statements, add the line

#define CHILDREN 2

That defines the constant CHILDREN and sets it equal to 2. Note that in C, this type of definition does not end with a semi-colon.

2.

Read the man pages for the fork and wait system calls. If you want to print a man page, you use the -t option, as in man -t fork. The result is a Postscript version of the man page, which you can redirect into a file and then print, or you can pipe it directly to lpr:

man -t fork | lpr

3.

Modify the program so that instead of creating a single child it creates as many children as the value of CHILDREN, such that all the children are running at the same time. Each child should print a message like, ``Hello from child 2.'' (Or whatever number the child happens to be).

WARNING: please be careful when you write this part of the program, to make sure that the fork command is not contained in an infinite loop. If you create a very large number of processes, you can make the machine very slow, or even crash it.

4.

The parent should wait for all its children to exit before it exits. It should print a message acknowledging the death of each child.

5.

What do you notice about the order of the messages from the children? What does that tell you about the scheduling policy on this machine?