mysql 幻读，脏读和不可重复读

使用消息队列实现的2个终端之间的互相聊天

并使用信号控制消息队列的读取方式：

当键盘按ctrl+c的时候，切换消息读取方式，一般情况为读取指定编号的消息，

按ctrl+c之后，指定的编号不读取，读取其他所有编号的消息

1.c

typedef struct msgbuf{
    long type;
    char text[256];
}msg_t;

// 写进程
int msgid = 0;

void* task(void* arg){
     msg_t buf = {0};
    int len = 0;
     while(1){
        memset(&buf,0,sizeof(msg_t));
         len = msgrcv(msgid,&buf,256,2,0);
        if(len == 0){break;}
         printf("\033[11D读取到的数据为:%s\n",buf.text);
        printf("请输入:");
        fflush(stdout);
     }
}

int main(int argc, const char *argv[])
{
    pthread_t id;
    pthread_create(&id,NULL,task,NULL);
    pthread_detach(id);

    key_t key = ftok("./ipc",1);
    if(key == -1){
        perror("ftok");
        return 1;
    }

    msgid = msgget(key,IPC_CREAT | 0666);
    if(msgid == -1){
        perror("msgget");
        return 1;
    }

    msg_t buf = {0};
    int len = 0;
    while(1){
        memset(&buf,0,sizeof(msg_t));
        buf.type = 1;
        printf("请输入内容:");
        scanf("%256s",buf.text);
        while(getchar()!=10);
        len = strlen(buf.text);
        msgsnd(msgid,
    }


    return 0;
}

2.c

typedef struct msgbuf{
    long type;
    char text[256];
}msg_t;

// 写进程
int msgid = 0;

void* task(void* arg){
     msg_t buf = {0};
    int len = 0;
     while(1){
        memset(&buf,0,sizeof(msg_t));
         len = msgrcv(msgid,&buf,256,1,0);
        if(len == 0){break;}
         printf("\033[11D读取到的数据为:%s\n",buf.text);
        printf("请输入:");
        fflush(stdout);
     }
}

int main(int argc, const char *argv[])
{
    pthread_t id;
    pthread_create(&id,NULL,task,NULL);
    pthread_detach(id);

    key_t key = ftok("./ipc",1);
    if(key == -1){
        perror("ftok");
        return 1;
    }

    msgid = msgget(key,IPC_CREAT | 0666);
    if(msgid == -1){
        perror("msgget");
        return 1;
    }

    msg_t buf = {0};
    int len = 0;
    while(1){
        memset(&buf,0,sizeof(msg_t));
        buf.type = 2;
        printf("请输入内容:");
        scanf("%256s",buf.text);
        while(getchar()!=10);
        len = strlen(buf.text);
        msgsnd(msgid,
    }


    return 0;
}