我想做一个程序在C接收消息队列中的消息。我有现有的代码在这里：

typedef struct {
    long id;
    char mes[20];
} message;

int main() {
    
    key_t cle = ftok(".",0);
    
    if(cle == -1){
        perror("ftok");
        return -1;
    }
    
    int msqId = msgget(cle, IPC_CREAT | IPC_EXCL ) ;
    if (msqId == -1) {
        msqId = msgget(cle, IPC_EXCL);
        if (msqId == -1) {
            perror("msgget");
            return -1;
        }
    }

    message mes;

    while (1) {
        int received = msgrcv(msqId, &mes, sizeof(message)-sizeof(long), 0, 0);
        
        if(received == -1){
            perror("msgrcv");
            return -1;
        }
        
        printf ("Server: message received.\n");
    }

    return 0;
}

它给出了以下错误：msgrcv：权限被拒绝
我还尝试使用以下命令更改 ftok 的路径：“/tmp”、“/etc/密码”