【原创】《Linux高级程序设计》杨宗德著 - 进程管理与程序开发 - System V进程间通信之消息队列
消息队列IPC原理
消息队列数据结构struct msqid_ds
消息队列数据结构struct msg_msg
Linux消息队列管理
1. 创建消息队列
2. 消息队列属性控制
3. 发送消息到消息队列
4. 从消息队列接收消息
消息队列应用示例
1. 示例代码 - 读取消息队列基本信息
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<string.h>
#include<sys/msg.h>
#define BUFSIZE 128
struct msg_buf
{
long type;
char msg[BUFSIZE];
};
int main(int argc,char *argv[])
{
key_t key;
int msgid;
struct msg_buf msg_snd,msg_rcv;
struct msginfo buf;
char *ptr="helloworld";
memset(&msg_snd,'\0',sizeof(struct msg_buf));
memset(&msg_rcv,'\0',sizeof(struct msg_buf));
msg_rcv.type=1;
msg_snd.type=1;
memcpy(msg_snd.msg,ptr,strlen(ptr));
if((key=ftok(".",'A'))==-1)
{
perror("ftok");
exit(EXIT_FAILURE);
}
if((msgid=msgget(key,0600|IPC_CREAT))==-1)
{
perror("msgget");
exit(EXIT_FAILURE);
}
printf("msgsnd_return=%d\n",msgsnd(msgid,(void *)&msg_snd,strlen(msg_snd.msg),0));
msgctl(msgid,MSG_INFO,&buf);
printf("buf.msgmax=%d\n",buf.msgmax);
printf("buf.msgmnb=%d\n",buf.msgmnb);
printf("buf.msgpool=%d\n",buf.msgpool);
printf("buf.semmap=%d\n",buf.msgmap);
printf("buf.msgmni=%d\n",buf.msgmni);
printf("buf.msgssz=%d\n",buf.msgssz);
printf("buf.msgtql=%d\n",buf.msgtql);
printf("buf.msgseg=%u\n",buf.msgseg);
printf("msgrcv_return=%d\n",msgrcv(msgid,(void *)&msg_rcv,BUFSIZE,msg_rcv.type,0));
printf("rev msg:%s\n",msg_rcv.msg);
printf("msgctl_return=%d\n",msgctl(msgid,IPC_RMID,0));
}
运行结果：
$ ./msg_ipc_info msgsnd_return=0 buf.msgmax=8192 buf.msgmnb=16384 buf.msgpool=2 buf.semmap=1 buf.msgmni=1736 buf.msgssz=16 buf.msgtql=10 buf.msgseg=16384 msgrcv_return=10 rev msg:helloworld msgctl_return=0
2. 使用消息队列实现实时通信
发送端：
#include<stdio.h>
#include<stdlib.h>
#include<sys/ipc.h>
#include<sys/msg.h>
#include<string.h>
struct msgbuf{
int type;char ptr[0];
};
int main(int argc,char *argv[]){
key_t key;key=ftok(argv[1],100);
int msgid;msgid=msgget(key,IPC_CREAT|0600);
pid_t pid;pid=fork();
if(pid==0){
while(1){
printf("pls input msg to send:");char buf[128];fgets(buf,128,stdin);
struct msgbuf *ptr=malloc(sizeof(struct msgbuf)+strlen(buf)+1);
ptr->type=1;memcpy(ptr->ptr,buf,strlen(buf)+1);
msgsnd(msgid,ptr,strlen(buf)+1,0);free(ptr);
}
}
else{
struct msgbuf{
int type;char ptr[1024];
};
while(1){
struct msgbuf mybuf;memset(&mybuf,'\0',sizeof(mybuf));
msgrcv(msgid,&mybuf,1024,2,0); printf("recv msg:%s\n",mybuf.ptr);
}
}
}
接收端：
#include<stdio.h>
#include<stdlib.h>
#include<sys/ipc.h>
#include<sys/msg.h>
#include<string.h>
struct msgbuf{
int type;
char ptr[0];
};
int main(int argc,char *argv[])
{
key_t key;
key=ftok(argv[1],100);
int msgid;
msgid=msgget(key,IPC_CREAT|0600);
pid_t pid;
pid=fork();
if(pid==0) //send
{
while(1)
{
printf("pls input msg to send:");
char buf[128];
fgets(buf,128,stdin);
struct msgbuf *ptr=malloc(sizeof(struct msgbuf)+strlen(buf)+1);
ptr->type=2; //send msg type=2
memcpy(ptr->ptr,buf,strlen(buf)+1);
msgsnd(msgid,ptr,strlen(buf)+1,0);
free(ptr);
}
}
else
{
struct msgbuf{
int type;
char ptr[1024];
};
while(1)
{
struct msgbuf mybuf;
memset(&mybuf,'\0',sizeof(mybuf));
msgrcv(msgid,&mybuf,1024,1,0); //recv msg type=2
printf("recv msg:%s\n",mybuf.ptr);
}
}
}发送端 - 终端1，运行结果：
$ ./msg_sender_example pls input msg to send:123 pls input msg to send:456 pls input msg to send:789 pls input msg to send:1234 pls input msg to send:接收端 - 终端2 - 运行结果：
$ ./msg_receiver_example recv msg:123 recv msg:456 recv msg:789 recv msg:1234
发送端 - 终端1，运行结果：
pls input msg to send:abc pls input msg to send:def pls input msg to send:ghi pls input msg to send:klm接收端 - 终端2 - 运行结果：
recv msg:abc recv msg:def recv msg:ghi recv msg:klm
需要强调的是，发送端和接收端的消息队列标识符要一致，以确保消息访问的队列一致，如果发送端和接收端消息队列不一致，则无法实现通信。
原文链接：
http://blog.csdn.net/geng823/article/details/41010115