1> 使用消息队列完成两个进程之间相互通信

snd.c

#include <myhead.h>

struct msgbuf
{
	long mtype;
	char mtext[1024];
};

#define SIZE sizeof(struct msgbuf)-sizeof(long)

int main(int argc,const char *argv[])
{
	pid_t pid = fork();
 	if(pid==-1)
 	{
		perror("fork error");
		return -1;
	}		
	else if(pid==0)
	{
		//子进程
		key_t key = ftok("/",'k');
		int msqid = msgget(key,IPC_CREAT|0644);
		if(msqid==-1)
		{
			perror("msgget error");
			return -1;
		}
		struct msgbuf buf;
		while(1)                  //接受类型2消息
		{
			msgrcv(msqid,&buf,SIZE,2,0);
			if(strcmp(buf.mtext,"quit")==0)
			{
				break;
			}
			printf("收到消息:%s\n",buf.mtext);
		}
		exit(EXIT_SUCCESS);
	}
	//父进程
	key_t key = ftok("/",'k');
	int msqid = msgget(key,IPC_CREAT|0644);
	if(msqid==-1)
	{
		perror("msgget error");
		return -1;
	}
	struct msgbuf buf;
	while(1)               //发送类型1消息
	{
		fgets(buf.mtext,SIZE,stdin);
		buf.mtext[strlen(buf.mtext)-1]=0;
		buf.mtype=1;
		msgsnd(msqid,&buf,SIZE,0);
		if(strcmp(buf.mtext,"quit")==0)
		{
			break;
		}
	}
	
	wait(NULL);
    return 0;
}

recv.c

#include <myhead.h>

struct msgbuf
{
	long mtype;
	char mtext[1024];
};

#define SIZE sizeof(struct msgbuf)-sizeof(long)

int main(int argc,const char *argv[])
{
 	pid_t pid = fork();
 	if(pid==-1)
 	{
		perror("fork error");
		return -1;
	}		
	else if(pid==0)
	{
		//子进程
		key_t key = ftok("/",'k');
		int msqid = msgget(key,IPC_CREAT|0644);
		if(msqid==-1)
		{
			perror("msgget error");
			return -1;
		}
		struct msgbuf buf;
		while(1)                   //发送类型2消息
		{
			fgets(buf.mtext,SIZE,stdin);
			buf.mtext[strlen(buf.mtext)-1]=0;
			buf.mtype=2;
			msgsnd(msqid,&buf,SIZE,0);
			if(strcmp(buf.mtext,"quit")==0)
			{
				break;
			}
		}
		exit(EXIT_SUCCESS);
	}
	key_t key = ftok("/",'k');
	int msqid = msgget(key,IPC_CREAT|0644);
	if(msqid==-1)
	{
		perror("msgget error");
		return -1;
	}
	struct msgbuf buf;
	while(1)                         //接受类型1消息
	{
		msgrcv(msqid,&buf,SIZE,1,0);
		if(strcmp(buf.mtext,"quit")==0)
		{
			break;
		}
		printf("收到消息:%s\n",buf.mtext);
	}

	wait(NULL);
    if(msgctl(msqid,IPC_RMID,NULL)==-1)
	{
		perror("msgctl error");
		return -1;
	}
    return 0;
}

2> 将共享内存的实现重新敲一遍

snd.c

#include<myhead.h>
#include<sys/user.h>

int main(int argc, const char *argv[])
{
    //1、创建key值用于创建共享内存段
    key_t key = ftok("/", 't');
    if(key == -1)
    {
        perror("ftok error");
        return -1;
    }

    printf("key = %d\n", key);

    //2、创建一个共享内存的对象
    int shmid = shmget(key, PAGE_SIZE, IPC_CREAT|0664);
    if(shmid == -1)
    {
        perror("shmget error");
        return -1;
    }
    printf("shmid = %d\n", shmid);

    //3、将共享内存段映射到程序中来
    char *addr = (char *)shmat(shmid, NULL, 0);

    printf("addr = %p\n", addr);         //输出映射的地址

    //向共享内存中写入数据
    strcpy(addr, "hello a hua qing yuan jian\n");

    sleep(5);

    //取消映射关系
    if(shmdt(addr) ==-1)
    {
        perror("shmdt error");
        return -1;
    }

    while(1);
    return 0;
}

recv.c

#include<myhead.h>
#include<sys/user.h>

int main(int argc, const char *argv[])
{
    //1、创建key值用于创建共享内存段
    key_t key = ftok("/", 't');
    if(key == -1)
    {
        perror("ftok error");
        return -1;
    }

    printf("key = %d\n", key);

    //2、创建一个共享内存的对象
    int shmid = shmget(key, PAGE_SIZE, IPC_CREAT|0664);
    if(shmid == -1)
    {
        perror("shmget error");
        return -1;
    }
    printf("shmid = %d\n", shmid);

    //3、将共享内存段映射到程序中来
    char *addr = (char *)shmat(shmid, NULL, 0);

    printf("addr = %p\n", addr);         //输出映射的地址

    //读出共享内存中的数据
    printf("消息为：%s", addr);

    sleep(5);
    if(shmdt(addr) == -1)
    {
        perror("shmdt error");
        return -1;
    }

    //删除共享内存
    if(shmctl(shmid, IPC_RMID, NULL) == -1)
    {
        perror("shmctl error");
        return -1;
    }
    while(1);
    return 0;
}

 思维导图