How to get return value from CHILD PROCESS?

Program calculates sum of numbers from 1 to N.. Child process calculates sum of EVEN numbers. Parent process calculates sum of odd numbers. I want to get the return value of child process in parent process. How do i do that ``` #include<stdio.h> #include<errno.h> #include<unistd.h> #include<stdlib.h> #include<fcntl.h> int main() { int N; int id; int fd_result;; printf("Enter N till which you want the sum: \n"); scanf("%d",&N); if ((fd_result=creat("result", 600))== -1) { perror("Error creating file"); exit(1); } if ((fd_result=open("result",O_TRUNC | O_RDWR)) == -1) { perror("Error Opening file"); exit(1); } if ((id=fork())<0) { perror("Error occurred forking....!"); exit(errno); } if (id == 0) { int i; int sum=0; for (i=0;i<=N;i=i+2) sum+=i; printf("Child sum: %d",sum); if (write(fd_result,&sum,sizeof(int))==-1) perror("Error writing to file"); _exit(0); } if (id > 0) { int i; int sum=0; int sum_odd; for (i=1;i<=N;i=i+2) sum+=i; lseek(fd_result,0,SEEK_SET); read(fd_result,&sum_odd,sizeof(int)); printf("\nThe sum is: %d",sum+(int)sum_odd); } close(fd_result); return 0; } ``` Pls tell me how do I get the return value of child process?