1.消息隊列結構體的定義

typedef struct{
uid_t uid; /* owner`s user id */
gid_t gid; /* owner`s group id */
udi_t cuid; /* creator`s user id */
gid_t cgid; /* creator`s group id */
mode_t mode; /* read-write permissions 0400 MSG_R 0200 MSG_W*/
ulong_t seq; /* slot usage sequence number*/
}ipc_perm;

typedef stuct{
struct ipc_perm msg_perm; /* read_write perms */
struct msg *msg_first; /* ptr to first message on queue */
struct msg *msg_last; /* ptr to last message on queue */
msglen_t msg_cbytes; /* used bytes current on queue */
msgqnum_t msg_qnum; /* current num of message on queue */
msglen_t msg_qbytes; /* max # of bytes allowed on queue */
pid_t msg_lspid; /* pid of last msgsnd() */
pid_t msg_lrpid; /* pid of last msgrcv() */
time_t msg_stime; /* time of last msgsnd() */
time_t msg_rtime; /* time of last msgrcv() */
time_t msg_ctime; /* time of last msgctl() */
}msqid_ds;

typedef struct
{
long mtype;
char mbuf[MSGLEN];
}Message;

2.創建消息隊列：

/***************************************************
Function:
int msgget(ket_t key,int oflag);
Explain:
create or view a message queue
Return :
a int indetify
Include:
sys/msg.h
introduction:
oflag: 0400 msg_r
0200 msg_w
0600 msg_wr
ipc_creat: NO exist and then creat a queue
exist : reference a queue
ipc_creat|ipc_excl: NO exist and then creat a queue
exist : return error
****************************************************/
#include<stdio.h>
#include<sys/msg.h>
#include<stdlib.h>

int MsgGet(int key)
{
int ret;
ret=msgget(key,0600|IPC_CREAT);
// ret=msgget(key,0600|IPC_CREAT|IPC_EXCL);
if(ret<0)
perror("creat msgid error");
printf("msgid=%d/n",ret);
system("ipcs -q -i ret");
return ret;
}
int main(int argc,char *agrv[])
{
int key;
printf("pleasse input msgkey:");
scanf("%d",&key);
MsgGet(key);
return 0;
}

3.向消息隊列中發送消息msgsnd

/***********************************************************************************
Function:
int msgsnd(int msqid,const void *ptr,size_t length,int flag)
Explain:
send a message to a queue
Return:
len: send message len;
Include:
sys/msg.h
Introduction:
flag: 0 : if queue full wait:1>具備存放新消息的空間
2>由msqid標識的消息隊列從系統中刪除(返回EIDRM錯誤)
3>調用線程被某個捕獲的信號所中斷(返回EINTR錯誤)
IPC_NOWAIT:如果沒有存放新消息的空間,函數馬上返回
1>指定的隊列中有太多的字節
2>在系統範圍存在太多的消息
*****************************************************************************************/
#include "typemsg.h"
int MsgSnd(int msqid,char *buf,int len,int flag)
{
int ret;
ret=msgsnd(msqid,buf,len,flag);
if(ret<0)
perror("msgsnd error");
system("ipcs -q");
return ret;
}

int main()
{
int msqid,len,stype;
Message msgb;
memset(&msgb,0,sizeof(Message));
printf("msgsnd:please input msqid:");
scanf("%d",&msqid);
printf("please input msgtype:");
scanf("%d",&stype);
msgb.mtype=stype;
strcpy(msgb.mbuf,"zhangweia");
MsgSnd(msqid,(char *)&msgb,sizeof(Message),0);
return 0;
}

4.從隊列中獲取消息 msgrcv

/*********************************************************************
Function:
int msgrcv(int msqid,const void *ptr,size_t msglen,long type,int flag)
Explain:
recv message order by type
msgrcv error: Argument list too long --> msglen的長度小於消息體中消息的長度
Para :
ptr: point to message struct
msglen: 由ptr指向的緩沖區中數據部分的大小,這個是該函數能夠返回的最大數據量
type: message type;

1> 0:返回隊列中最早的消息
2> 大於0:返回消息隊列中類型為type的第一個消息
3> 小於0:返回消息隊列中類型小於或者等於type的絕對值的消息類型中最小的第一個消息
flag: 0<wait> 沒有消息或者消息類型不符合的時候,線程等待
響應: 1>有一個所請求類型的消息可以獲取
2>msqid的消息隊列被系統刪除,返回一個EIDRM
3>調用線程被某個捕獲的信號所中斷
IPC_NOWAIT:在沒有數據的情況下,立即返回一個ENOMSG錯誤
MSGNOERROR:當所接受的消息數據部分大於msglen長度時,獲取截短的數據部分,否則返回E2BIG錯誤
Return:
message len
*********************************************************************/
#include "typemsg.h"
int MsgRcv(int msqid,char *buf,int msglen,long type,int flag)
{
int ret;
ret=msgrcv(msqid,buf,msglen,type,flag);
if(ret<0)
perror("msgrcv error");
system("ipcs -q");
return ret;

}

int main()
{
int msqid,len;
long ttype;
Message mbuf;
printf("msgrcv:please input recv msqid:");
scanf("%d",&msqid);
MsgRcv(msqid,(char *)&mbuf,8900,0,IPC_NOWAIT);
printf("recv message=%s/n",mbuf.mbuf);
Put_String((unsigned char *)&mbuf,sizeof(Message));
return 0;
}

6.消息隊列的控制msgctl

/**********************************************************
Function:
int msgctl(int msqid,int cmd,struct msqid_ds *buff)
Explain:
cdm: IPC_RMID; delete msqid
IPC_SET:
IPC_STAT: return msqid stat

*********************************************************/
#include "typemsg.h"
int MsgCtl(int msqid,int cmd,struct msqid_ds *buff)
{
int ret;
ret=msgctl(msqid,cmd,buff);
if(ret<0)
{
perror("msgctl error");
return -1;
}
return 0;
}

int main()
{
int msqid,type;
struct msqid_ds info;
printf("please input msqid /nand type(1:icp_rmid;2:ipc_stat)");
scanf("%d%d",&msqid,&type);
if(type==1)
{
MsgCtl(msqid,IPC_RMID,NULL);
printf("delete queue success:%d/n",msqid);
}else if(type==2)
{
MsgCtl(msqid,IPC_STAT,&info);
printf("get queue stat:%d/n",msqid);
}
return 0;

}

消息隊列函數