该程序计算从1到N的数字总和。 子进程计算偶数的总和。 父进程计算奇数的总和。 我想在父进程中获取子进程的返回值。如何实现?
#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;
}
请告诉我如何获取子进程的返回值?