create queue

#include <sys/types.h>#include <sys/msg.h>#include <unistd.h>void msg_stat(int,struct msqid_ds );void main(){    int gflags,sflags,rflags;    key_t key;    int msgid;    int reval;    struct msgsbuf{            int mtype;            char mtext[1];        }msg_sbuf;    struct msgmbuf        {        int mtype;        char mtext[10];        }msg_rbuf;    struct msqid_ds msg_ginfo,msg_sinfo;    char* msgpath="/home/wulei/wulei/ipc.c";    key=ftok(msgpath,'a');    printf("key is %x",key);    gflags=IPC_CREAT|IPC_EXCL;    msgid=msgget(key,gflags|00666);    if(msgid==-1)    {        printf("msg create error\n");        msgid=msgget(key,0);        if (-1==msgid)        {            printf("111111111\n");            return;        }    }    //创建一个消息队列后，输出消息队列缺省属性    printf("\nOutput 1:");    msg_stat(msgid,msg_ginfo);    sflags=IPC_NOWAIT;    msg_sbuf.mtype=10;    msg_sbuf.mtext[0]='a';    reval=msgsnd(msgid,&msg_sbuf,sizeof(msg_sbuf.mtext),sflags);    if(reval==-1)    {        printf("message send error\n");    }    //发送一个消息后，输出消息队列属性    printf("\nOutput 2:%c",msg_sbuf.mtext[0]);        msg_stat(msgid,msg_ginfo);#if 0    rflags=IPC_NOWAIT|MSG_NOERROR;    reval=msgrcv(msgid,&msg_rbuf,4,10,rflags);    if(reval==-1)        printf("read msg error\n");    else        printf("read from msg queue %d bytes\n",reval);    printf("\nrcv type =%d,msg =%c",msg_rbuf.mtype,*(msg_rbuf.mtext));    //从消息队列中读出消息后，输出消息队列属性#endif    printf("\nOutput 3:");    msg_stat(msgid,msg_ginfo);    msg_sinfo.msg_perm.uid=8;//just a try    msg_sinfo.msg_perm.gid=8;//    msg_sinfo.msg_qbytes=16388;    //此处验证超级用户可以更改消息队列的缺省msg_qbytes    //注意这里设置的值大于缺省值    reval=msgctl(msgid,IPC_SET,&msg_sinfo);    if(reval==-1)    {        printf("msg set info error\n");        //return;    }        printf("\nOutput 4:");    msg_stat(msgid,msg_ginfo);    //验证设置消息队列属性#if 0    reval=msgctl(msgid,IPC_RMID,NULL);//删除消息队列    if(reval==-1)    {        printf("unlink msg queue error\n");        return;    }#endif}void msg_stat(int msgid,struct msqid_ds msg_info){    int reval;    sleep(1);//只是为了后面输出时间的方便    reval=msgctl(msgid,IPC_STAT,&msg_info);    if(reval==-1)    {        printf("get msg info error\n");        return;    }    printf("\n");    printf("current number of bytes on queue is %d\n",msg_info.msg_cbytes);    printf("number of messages in queue is %d\n",msg_info.msg_qnum);    printf("max number of bytes on queue is %d\n",msg_info.msg_qbytes);    //每个消息队列的容量（字节数）都有限制MSGMNB，值的大小因系统而异。在创建新的消息队列时，//msg_qbytes的缺省值就是MSGMNB    printf("pid of last msgsnd is %d\n",msg_info.msg_lspid);    printf("pid of last msgrcv is %d\n",msg_info.msg_lrpid);    printf("last msgsnd time is %s", ctime(&(msg_info.msg_stime)));    printf("last msgrcv time is %s", ctime(&(msg_info.msg_rtime)));    printf("last change time is %s", ctime(&(msg_info.msg_ctime)));    printf("msg uid is %d\n",msg_info.msg_perm.uid);    printf("msg gid is %d\n",msg_info.msg_perm.gid);}