2.进程间的管道通信

（一） 编写一个关于进程通信的简单程序，子进程送一串消息给父进程，父进程收到消息后把它显示出来。 要求： 两个子进程分别向管道写一句话： Child process 1 is sending a message! Child process 2 is sending a message! 而父进程则从管道中读出来自两

（一） 编写一个关于进程通信的简单程序，子进程送一串消息给父进程，父进程收到消息后把它显示出来。

要求：

两个子进程分别向管道写一句话：
Child process 1 is sending a message!

Child process 2 is sending a message!

而父进程则从管道中读出来自两个子进程的消息，显示屏幕上，且父进程要先接收子进程1的消息，在接受子进程2的消息。

#include
#include
#include
#define SIZE 50
int main()
{
	int p1, p2;
	int fd[2];
	char str[50];
	while((pipe(fd)) == -1);
	while((p1 = fork()) == -1);
	if(p1)
	{
		while((p2 = fork()) == -1);
		if(p2)
		{
			//parent
			wait(0);
			read(fd[0], str, SIZE);
			printf("%s\n", str);
			wait(0);
			read(fd[0], str, SIZE);
			printf("%s\n", str);
		}
		else
		{
			//child2
			lockf(fd[1], 1, 0);
			sleep(2);
			strcpy(str, "Child process 2 is sending messages!\n");
			write(fd[1], str, SIZE);
			lockf(fd[1], 0, 0);
		}
	}
	else
	{
		//child1
		lockf(fd[1], 1, 0);
		sleep(2);
		strcpy(str, "Child process 1 is sending messages!\n");
		write(fd[1], str, SIZE);
		//sleep(2);
		lockf(fd[1], 0, 0);

	}
}

#include
#include
#include
#define SIZE 50
int main()
{
	int p, fd[2];
	int i = 0;
	char str[SIZE];
	while((pipe(fd)) == -1);
	while((p = fork()) == -1);
	if(p)
	{
		//parent
		lockf(fd[1], 1, 0);
		printf("Please input the string:");
		scanf("%s", str);
		write(fd[1], str, SIZE);
		lockf(fd[1], 0, 0);
		wait(0);

		read(fd[0], str, SIZE);
		printf("reversed string is : %s\n", str);
	}
	else
	{
		read(fd[0], str, SIZE);
		while(str[i] != '\0')
		{
			if('A' <= str[i] && str[i] <= 'Z')
			{
				str[i] += 32;
			}
			else if('a' <= str[i] && str[i] <= 'z')
			{
				str[i] -= 32;
			}
			i++;
		}
		write(fd[1], str, SIZE);
	}
	return 0;
}