使用消息队列实现两个进程间的相互通信

A:

#include <head.h>
struct msgbuf {
           long mtype; //消息类型
           char mtext[1024];//正文数据
       };
#define SIZE sizeof(struct msgbuf)-sizeof(long)
int main(int argc, const char *argv[])
{ 
	pid_t ap=fork();
	if(ap>0)
	{
	key_t key=ftok("./",'k');
	if(key==-1)
	{
		perror("ftok");
		return -1;
	}
	int msgid;//消息队列号
	if((msgid=msgget(key,IPC_CREAT|0664))==-1)
	{
		perror("msgget");
		return -1;
	}
	struct msgbuf info={.mtype=50};
	while(1)
	{
		bzero(info.mtext,sizeof(info.mtext));
		printf("A请输入：");
		fgets(info.mtext,SIZE,stdin);	
		info.mtext[strlen(info.mtext)-1]=0;
		msgsnd(msgid,&info,SIZE,0);
		if((strcmp(info.mtext,"q"))==0)
		{
			printf("A写退出\n");
			break;
		}

			}
		}
	else if(ap==0)
	{	

	key_t key=ftok("./",'k');
	if(key==-1)
	{
		perror("ftok");
	 	return -1;
	}
	int msgid;
	if((msgid=msgget(key,IPC_CREAT|0664))==-1)
	{
		perror("msgid");
		return-1;
	}
	struct msgbuf info;
	while(1)
	{
		bzero(info.mtext,sizeof(info.mtext));
		msgrcv(msgid,&info,SIZE,100,0);
		printf("B消息为：%s\n",info.mtext);
		if((strcmp(info.mtext,"q"))==0)
		{
			printf("B退出\n");
			break;
		}
	}
	exit(0);
	}
	else
	{
		perror("fork");
		return -1;
	}
	return 0;
} 

B:

#include <head.h>
struct msgbuf {
           long mtype; //消息类型
		   char mtext[1024];//正文数据
       };
#define SIZE sizeof(struct msgbuf)-sizeof(long)
int main(int argc, const char *argv[])
{
	pid_t bp=fork();
	if(bp>0)
	{
	key_t key=ftok("./",'k');
	if(key==-1)
	{
		perror("ftok"); 
		return -1;
	}
	int msgid;
	if((msgid=msgget(key,IPC_CREAT|0664))==-1)
	{
		perror("msgget");
		return -1;
	}
	struct msgbuf info={.mtype=100};
	while(1)
	{
		bzero(info.mtext,sizeof(info.mtext));
		printf("B请输入：");
		fgets(info.mtext,SIZE,stdin);	
		info.mtext[strlen(info.mtext)-1]=0;
		msgsnd(msgid,&info,SIZE,0);
		if((strcmp(info.mtext,"q"))==0)
		{
			printf("B写退出\n");
			break;
		}

		}
	}
	
	else if(bp==0)
	{
		key_t key=ftok("./",'k');
	if(key==-1)
	{
		perror("ftok");
		return -1;
	}
	int msgid;//消息队列号
	if((msgid=msgget(key,IPC_CREAT|0664))==-1)
	{
		perror("msgget");
		return -1;
	}
	struct msgbuf info;
	while(1)
	{
		bzero(info.mtext,sizeof(info.mtext));
		msgrcv(msgid,&info,SIZE,50,0);
		printf("A消息为：%s\n",info.mtext);
		if((strcmp(info.mtext,"q"))==0)
		{
		printf("A写退出\n");
		break;
		}
	}
	exit(0);
	}
	else
	{
		perror("fork");
		return -1;
	}
	return 0;
}