Question

The Fibonacci sequence is the series of numbers 0, 1, 1, 2, 3, 5, 8, .... It is defined by

the following mathematical expression, with X0 & X1 being 0 and 1, respectively:

Xn = Xn-1 + Xn-2

Write a C program using the fork() system call that generates and prints the Fibonacci

sequence in the child process. The number of members in the sequence will be

determined by a user provided as a user prompted input. Make the parent process wait

for the child process to complete before exiting. Make the program print both the

parent and child process IDs. The program should perform the necessary error checking

to only accept positive integers from the user. A failure of fork() should be caught and

printed as an error message using err_sys call.

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
void err_sys(const char* x)
{
   perror(x);
   exit(1);
}

int main(){

int n, f, c, i;
int *arr;
printf("Enter number of terms: ");
scanf("%d", &n);
arr = (int*) malloc(n* sizeof(int));

arr[0] = 0;
arr[1] = 1;

f= fork();

if(f < 0)
{

err_sys("Fork failed");
}

else if(f ==0){
//child process

for(i=0; i<n; i++)
{
    if(i != 0 && i !=1)
       arr[i] = arr[i-1] + arr[i-2];

    printf("%d ",arr[i]);
}
}

else{
    //parent process

    c = wait(NULL);
    printf("\n Child process ID %d \n", c);
    printf(" Parent process ID %d\n", getpid());
}

return 0;
}