Write a program simulating an alarm clock.

Question

Write a program simulating an alarm clock. In the main function, you fork a child process, and the child process sleeps for 5 seconds (the number of seconds is an command line argument, see below for a sample run), after which the child process sends the signal (SIGALRM) to its parent process. The parent process, after forking the child process, pause, upon receiving the SIGALRM signal, process prints out a message “Ding!”.

The following is a sample run $./alarm 5

alarm application running

waiting for alarm to go off

<5 second pause>

Ding! Done!

Answer 1

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/wait.h>

// this is signal handler for

void signalHandler(int signal)

{

        if (signal == SIGALRM)

    {

        printf("Ding!\n");

                wait(NULL);

            

    }

}

int main(int argc, char *argv[])

{

        signal(SIGALRM, signalHandler);

    if (argc != 2)

    {

        printf("Invalid arguments\n");

        return 0;

    }

    printf("Alarm application starting\n");

    int delay;

    // compute delay

    sscanf(argv[1], "%d", &delay);

    // start child process

    if (fork() == 0)

    {

        printf("Waiting for alarm to go off\n");

        sleep(delay);

        kill(getppid(), SIGALRM);

        exit(0);

    }

    wait(NULL);

    printf("done\n");

}