控制消息队列权限

#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <sys/ipc.h>#include <sys/msg.h>#include <errno.h>#include <string.h>#include <sys/shm.h>typedef struct{long int nType;char szText[256];}MSG;int main(int argc, char** argv) {    key_t IKey1;    int n,nMsgId;    MSG msg;    struct msqid_ds qds;    if((IKey1 = ftok("/etc/profile",1)) == -1)    {        perror("ftok");        exit(1);    }        if((nMsgId = msgget(IKey1,0)) == -1)    {        perror("msgget");        exit(2);    }          memset(&qds,0x00,sizeof(struct msqid_ds));    if(msgctl(nMsgId,IPC_STAT,&qds));    {        //perror("msgctl IPC_STAT");        printf("error happen\n");        exit(3);    }    printf("msg_perm.mode=%d\n",qds.msg_perm.mode);        qds.msg_perm.mode &=(~0222);        if(msgctl(nMsgId,IPC_SET,&qds)<0)    {         perror("msgctl IPC_SET");        exit(3);    }        memset(&msg,0x00,sizeof(MSG));    msg.nType=2;    memcpy(msg.szText,"12345",5);        if((n = msgsnd(nMsgId,(const void*)&msg,5,0))<0)    {        perror("msgsnd");    }        if(msgctl(nMsgId,IPC_RMID,NULL)<0){        perror("msgctl IPC_RMID");        exit(5);    }      return 0;}