消息队列

消息队列的用法

例1: 两个进程之间传输数据

server.c

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <termios.h>
#include <signal.h>

#include "msg.h"

#define ERROR(flag,msg)                 \
     if(flag)                \
    {                    \
        printf("%d: ",__LINE__);    \
        fflush(stdout);            \
        perror(msg);            \
        exit(errno);            \
    }

int main(int argc,char *argv[])
{
    int qid;
    int ret;
    key_t key;
    
    struct mymsgbuf msg;

    key = ftok(PATH_NAME,PROJ_ID);
    ERROR(key == -1,"ftok");

    qid = msgget(key,MSG_FLAG);
    ERROR(qid == -1,"msgget");

    char s[] = "please input msg:     ";

    while(1)
    {
        write(STDOUT_FILENO,s,sizeof(s));
        
        ret = read(STDIN_FILENO,msg.mtext,BUF_SIZE);
        if(strncmp(msg.mtext,"q",1) == 0)
            break;
        
        msg.mtype = SERVER;
        msg.mtext[ret - 1] = 0;

        ret = msgsnd(qid,&msg,ret,0);
        if(ret == -1)
            break;
                
        ret = msgrcv(qid,&msg,BUF_SIZE,CLIENT,0);
        if(ret == -1)
            break;

        printf("receive from client:  %s\n",msg.mtext);
    }

    msgctl(qid,IPC_RMID,NULL);

    return 0;
}

client.c

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <termios.h>
#include <signal.h>

#include "msg.h"

#define ERROR(flag,msg)                 \
     if(flag)                \
    {                    \
        printf("%d: ",__LINE__);    \
        fflush(stdout);            \
        perror(msg);            \
        exit(errno);            \
    }

int main(int argc,char *argv[])
{
    int qid;
    int ret;
    key_t key;
    
    struct mymsgbuf msg;

    key = ftok(PATH_NAME,PROJ_ID);
    ERROR(key == -1,"ftok");

    qid = msgget(key,MSG_FLAG);
    ERROR(qid == -1,"msgget");


    char s[] = "please input msg:     ";

    while(1)
    {
        ret = msgrcv(qid,&msg,BUF_SIZE,SERVER,0);
        if(ret == -1)
            break;

        printf("receive from server:  %s\n",msg.mtext);
        
        write(STDOUT_FILENO,s,sizeof(s));
        
        ret = read(STDIN_FILENO,msg.mtext,BUF_SIZE);
        if(strncmp(msg.mtext,"q",1) == 0)
            break;
        
        msg.mtype = CLIENT;
        msg.mtext[ret - 1] = 0;

        ret = msgsnd(qid,&msg,ret,0);
        if(ret == -1)
            break;
    }

    msgctl(qid,IPC_RMID,NULL);

    return 0;
}

另有一个公共的.h文件

#ifndef __MSG_H_
#define __MSG_H_

#include <sys/msg.h>

#define BUF_SIZE 256
#define PROJ_ID 32
//#define PATH_NAME "/etc/inittab"  //ubuntu has no inittab
#define PATH_NAME "/etc/passwd"
#define MSG_FLAG (IPC_CREAT | 0600)

#define SERVER 1
#define CLIENT 2

struct mymsgbuf {
    long mtype;
    char mtext[BUF_SIZE];
};

#endif

编译链接运行(先server后client), 结果如下:

 

msgctl()对消息队列的控制...略