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);
}