消息队列的基本使用思路和接口介绍

#include <stdlib.h>#include <errno.h>#include <string.h>#include <stdio.h>#include <unistd.h>#include <sys/ipc.h>#include <sys/msg.h>#include <sys/types.h>#define MSGLENGTH 256#define MSG 0010/* *消息队列，在不关闭的情况下，只要拿到id就可以读取内容，但是当执行过msgrcv后 * 该队列将被删除 **//*生成key用于创建消息队列*/key_t mk_id(int id){    static char path[128 +1];    static int flag=0;    key_t key ;    if( flag )        goto _not_first_;    sprintf(path,"%s/%s",getenv("HOME"),".bashrc");    flag = 1 ;_not_first_:    key = ftok(path,id);    return ( key );}/*销毁消息队列*/int Close_msg(int id){    return msgctl(id,IPC_RMID,0);}/*读取消息队列的内容*/int Recv_msg(int id,int p_no){    struct s_msg{            long type;            char mtext[256];    } msg;    int msg_len=0;    while(1)    {        msg_len=msgrcv(id,&msg,MSGLENGTH,0,IPC_NOWAIT|MSG_NOERROR);        /*消息读完了就break*/        if(errno == ENOMSG)            break;        /*读取消息出错*/        if(msg_len==-1 )        {            perror("msgrcv");            return -1;        }        printf("%d:%s\n",p_no,msg.mtext);    }    return 0;}int Write_msg(int id){    struct s_msg{            long type;            char mtext[256];    } msg;    char buff   [256];    char file_name   [256];    FILE *in_file;    int snd_len=0;    msg.type=MSG;    sprintf(file_name,"%s/%s",getenv("HOME"),"tmp/1.dat");    if((in_file=fopen(file_name,"r"))==NULL)    {        perror("fopen");        exit(-1);    }    while(fgets(buff,256,in_file) !=NULL)    {        memcpy((void *)msg.mtext,buff,MSGLENGTH);        /*复制string到消息队列*/        snd_len==msgsnd(id,&msg,MSGLENGTH,IPC_NOWAIT);        /*出现EAGAIN好像是队列没释放，等会儿就能放进去了*/        if(-1==snd_len && errno != EAGAIN)        {            perror("msgsnd");            exit(-1);        }        memset(msg.mtext,0x00,sizeof(msg.mtext));    }    fclose(in_file);    return 0;}/*创建消息队列*/int Creat_msg(key_t key){    int id=0;    if((id=msgget(key,0666|IPC_CREAT)) == -1)    {        perror("msgget");        exit(-1);    }    return id;}main(){    int id=0;    int proc_num=2;    pid_t pid=0;    id=Creat_msg(mk_id(MSG));    printf("msg id %d\n",id);    Write_msg(id);    /*2个线程同时读取消息队列*/    while(proc_num--)    {        pid=fork();        if(pid==0)        {            Recv_msg(id,proc_num);            exit(-1);        }        else if (pid <0)        {            perror("fork");            exit(-1);        }    }    /*等大家都读取完成后销毁队列*/    wait(NULL);    Close_msg(id);    exit(0);}