Linux消息队列应用

 

#include"sys/types.h"
#include "sys/msg.h"
#include "unistd.h"
#include"stdio.h"
void msg_stat(int,struct msqid_ds);

int main()
{
    int gflags,sflags,rflags;
    key_t key;
    int msgid;
    int reval;
    struct msgbuf{
        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="/UNIX/msgqueue";
    key=ftok(msgpath,'a');
    gflags=IPC_CREAT|IPC_EXCL;
    msgid=msgget(key,gflags|00666);
    if(msgid==-1){
        printf("msg create error!\n");
        return;
    }
    /*创建一个消息队列后，输出消息队列默认属性*/
    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*/
    msg_stat(msgid,msg_ginfo);
    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);
    /*从消息队列中读出消息后，输出消息队列属性*/
    msg_stat(msgid,msg_ginfo);
    msg_sinfo.msg_perm.uid=8;
    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默认msg_qbytes                     */
    //注意这里设置的值大于最大默认值
    /************************************************************************/
    reval=msgctl(msgid,IPC_SET,&msg_sinfo);
    if(reval==-1){
        printf("msg set info error!\n");
        return;
    }
    msg_stat(msgid,msg_ginfo);
    /************************************************************************/
    /* 验证设置消息队列属性                                                 */
    /************************************************************************/
    reval=msgctl(msgid,IPC_RMID,NULL);//删除消息队列
    if (reval==-1)
    {
        printf("unlink msg queue error!\n");
        return;
    }
}
void msg_stat(int msgid,struct msqid_ds msg_info)
{
    int reval;
    sleep(1);
    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 %ld \n",msg_info.msg_cbytes);
    printf("number of messages in the queue is %ld \n",msg_info.msg_qnum);
    printf("max number of bytes on queue id %ld \n",msg_info.msg_qbytes);
    /************************************************************************/
    /* 每个消息队列是容量（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_qtytes的默认值就是MSHMNB
    /************************************************************************/
    printf("pid of last msgsnd is %ld\n",msg_info.msg_lspid);
    printf("pid of last msgrcv is %ld \n",msg_info.msg_lrpid);
    printf("last msgcnd time is %s \n",ctime(&(msg_info.msg_stime)));
    printf("last msgrcv time is %s \n",ctime(&(msg_info.msg_rtime)));
    printf("last change time is %s \n",ctime(&(msg_info.msg_ctime)));
    printf("msg uid is %ld \n",msg_info.msg_perm.uid);
    printf("msg gid is %ld \n",msg_info.msg_perm.gid);
}