Objectives: work with signals, fork, waitpid, exit and exit handlers

$1)$ Install an exit handler that prints $$Process PID is exiting$$ where PID is obtained by calling getpid$()$

$2)$ Install a signal handler for SIGCHLD which reaps zombie children using waitpid$()($detailed below$).$

a$.$ waitpid$()$ should only be used in this signal handler and wait$()$ shouldn$$t be used in this program

b$.$ The handler should update a global count of reaped processes

c$.$ Print $$Parent says: child N reaped$$ where N is the child$$s exit status

$3)$ After installing handlers, the process should say $$Parent says: my PID is PID$($PID from getpid$())$

a$.$ Parent calls fork$()$ N times where N is a macro NUM$\_$CHILDREN

b$.$ Use a global variable to count forks that is incremented just before each fork

c$.$ Save your final program with N$=5,$ but it should work for any value from $5$ to $25$

d$.$ The parent should not delay in any way $($such as sleep$())$until all forks are completed

$4)$ The children should print $$Child says: child N with PID PID exiting$($N is fork count; PID from getpid$())$

a$.$ The child should exit using the fork count as the exit status

$5)$ The parent should be the last process to exit after reaping all zombie children.

a$.$ The parent must print $$Parent says: exiting$$ at the end of main then exit$()$ with status $0$

b$.$ To wait for the children to exit, use a loop that checks the global reap count updated by the signal handler. Do not use pause$()$ anywhere in the program which waits until a signal arrives $($this might cause the program to pause forever if it$$s called after the last child is reaped$).$

$6)$ When declaring variables, use volatile with any global accessed both inside and outside of a signal handler