程序代码：

#include <stdio.h>
#include <unistd.h>

int main()
{
    pid_t pid;
    if(pid=fork()==0)
        printf("child started\n");
    if(pid==0){
        // child process
        int i;
        for(i=0;i<10;i++){
            printf("working %d\n",i);
            sleep(1);
        }
        printf("done\n");
        return 0;
    }else{
        //parcal process exits immediately
        //so as to reparent the children.
        return 0;
    }
}