消息队列(linux)

转自：http://blog.csdn.net/lifan5/article/details/7588529

/*send.c*/  
#include <stdio.h>   
#include <sys/types.h>   
#include <sys/ipc.h>   
#include <sys/msg.h>   
#include <errno.h>   

#define MSGKEY 1024   
  
struct msgstru  
{  
   long msgtype;  
   char msgtext[2048];   
};  
  
main()  
{  
  struct msgstru msgs;  
  int msg_type;  
  char str[256];  
  int ret_value;  
  int msqid;  
  
  msqid=msgget(MSGKEY,IPC_EXCL);  /*检查消息队列是否存在*/  
  if(msqid < 0){  
    msqid = msgget(MSGKEY,IPC_CREAT|0666);/*创建消息队列*/  
    if(msqid <0){  
    printf("failed to create msq | errno=%d [%s]
",errno,strerror(errno));  
    exit(-1);  
    }  
  }   
   int c;
  while (1){  
    printf("input message type(end:0):");  
    scanf("%d",&msg_type);
                //while ( (c=getchar()) != '
' && c != EOF ) {;}  
    getchar(); 
    //fflush(stdin);  //C和C++的标准里从来没有定义过 fflush(stdin)
    if (msg_type == 0)  
       break;  
    printf("input medssage to be sent:");  
    //scanf ("%s",str); 
    fgets(str,1024,stdin); 
    msgs.msgtype = msg_type;  
    strcpy(msgs.msgtext, str);  
    /* 发送消息队列 */  
    ret_value = msgsnd(msqid,&msgs,sizeof(struct msgstru),IPC_NOWAIT);  
    if ( ret_value < 0 ) {  
       printf("msgsnd() write msg failed,errno=%d[%s]
",errno,strerror(errno));  
       exit(-1);  
    }  
  }  
  msgctl(msqid,IPC_RMID,0); //删除消息队列   
}

/*receive.c */  
#include <stdio.h>   
#include <sys/types.h>   
#include <sys/ipc.h>   
#include <sys/msg.h>   
#include <errno.h>   
  
#define MSGKEY 1024   
  
struct msgstru  
{  
   long msgtype;  
   char msgtext[2048];  
};  
  
/*子进程，监听消息队列*/  
void childproc(){  
  struct msgstru msgs;  
  int msgid,ret_value;  
  char str[512];  
    
  while(1){  
     msgid = msgget(MSGKEY,IPC_EXCL );/*检查消息队列是否存在 */  
     if(msgid < 0){  
        printf("msq not existed! errno=%d [%s]
",errno,strerror(errno));  
        sleep(2);  
        continue;  
     }  
     /*接收消息队列*/  
     ret_value = msgrcv(msgid,&msgs,sizeof(struct msgstru),0,0);  
     printf("text=[%s] pid=[%d]
",msgs.msgtext,getpid());  
  }  
  return;  
}  
  
void main()  
{  
  int i,cpid;  
  
  /* create 5 child process */  
  for (i=0;i<5;i++){  
     cpid = fork();  
     if (cpid < 0)  
        printf("fork failed
");  
     else if (cpid ==0) /*child process*/  
        childproc();  
  }  
}