2次使用fork避免产生僵尸进程和不去处理SIGCHLD信号

#include <unistd.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc,char *argv[])
{
        pid_t child = fork();

        if( child == -1 ) { //error
                printf("\nfork child error.");
                exit(0);
        } else if(child == 0){
                //exit(0);
                if ((child = fork()) < 0)
                        printf("fork error\n");
                else if (child > 0)
                {
//                      sleep(3);
                        exit(0);
                }
                sleep(5);
                printf("second child,parent pid %d\n",getppid());
                exit(0);
        }
//      sleep(3);       
        if (waitpid(child,NULL,0) != child)
                printf("waitpid error\n");
        sleep(10);
        exit(0);
        //sleep(600);

}