不用wait控制父子进程执行顺序

[myclass242]

我在看一本书，有这么一个题目：
Write another program using fork(). The child process should print “hello”; the parent process should print “goodbye”. You should try to ensure that the child process always prints first; can you do this without calling wait() in the parent?

我写了一个程序发现并不能实现题目要求，麻烦帮忙看看

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>

int main(void)
{
	int pipeFd1[2];
	int pipeFd2[2];
	if(-1 == pipe(pipeFd1))
	{
		perror("pipe fail");
		exit(EXIT_FAILURE);
	}
	if(-1 == pipe(pipeFd2))
	{
		perror("pipe fail");
		exit(EXIT_FAILURE);
	}
	
	
	pid_t pid = fork();
	if(pid < 0)
	{
		perror("fork fail");
		exit(EXIT_FAILURE);
	}
	else if(0 == pid)
	{
		int loops = 10;
		close(pipeFd1[1]);
		close(pipeFd2[0]);
		while(loops--)
		{
			char buf[2];
			printf("Hello ");
			//fflush(stdout);
			write(pipeFd2[1], "OK", 2);
			read(pipeFd1[0], buf, 2);
			if(strncmp(buf, "OK", 2))
			{
				fprintf(stderr,"pipe data error\n");
				kill(getppid(), SIGKILL);
				exit(EXIT_FAILURE);
			}
		}
	}
	else
	{
		int loops = 10;
		close(pipeFd1[0]);
		close(pipeFd2[1]);
		while(loops--)
		{
			char buf[2];
			read(pipeFd2[0], buf, 2);
			if(strncmp(buf, "OK", 2))
			{
				fprintf(stderr,"pipe data error\n");
				kill(pid, SIGKILL);
				exit(EXIT_FAILURE);
			}
			printf("Goodbye\n");
			//fflush(stdout);
			write(pipeFd1[1], "OK", 2);
		}
	}
	return 0;
}

[zhxianbin]

也可以用 信号量

[Allensb]

可以看看进程间通信。。

[Ingsuifon]

你这本书应该是《操作系统导论》

[辣椒油li]

强制父进程休眠1s可以吗？

[RedWolf1999]

/proc/sys/kernel/sched_child_runs_first 改为 1