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消息队列
int msgget(key_t, key, int msgflg);
int msgsend(int msgid, const void *msg_ptr, size_t msg_sz, int msgflg);
struct my_message{ long int message_type; /* The data you wish to transfer*/ };
int msgrcv(int msgid, void *msg_ptr, size_t msg_st, long int msgtype, int msgflg);
int msgctl(int msgid, int command, struct msgid_ds *buf);
struct msgid_ds { uid_t shm_perm.uid; uid_t shm_perm.gid; mode_t shm_perm.mode; };
#include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <errno.h> #include <sys/msg.h> struct msg_st { long int msg_type; char text[BUFSIZ]; }; int main() { int running = 1; int msgid = -1; struct msg_st data; long int msgtype = 0; //注意1 //建立消息队列 msgid = msgget((key_t)1234, 0666 | IPC_CREAT); if(msgid == -1) { fprintf(stderr, "msgget failed with error: %d\n", errno); exit(EXIT_FAILURE); } //从队列中获取消息，直到遇到end消息为止 while(running) { if(msgrcv(msgid, (void*)&data, BUFSIZ, msgtype, 0) == -1) { fprintf(stderr, "msgrcv failed with errno: %d\n", errno); exit(EXIT_FAILURE); } printf("You wrote: %s\n",data.text); //遇到end结束 if(strncmp(data.text, "end", 3) == 0) running = 0; } //删除消息队列 if(msgctl(msgid, IPC_RMID, 0) == -1) { fprintf(stderr, "msgctl(IPC_RMID) failed\n"); exit(EXIT_FAILURE); } exit(EXIT_SUCCESS); }
发送信息：
#include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <sys/msg.h> #include <errno.h> #define MAX_TEXT 512 struct msg_st { long int msg_type; char text[MAX_TEXT]; }; int main() { int running = 1; struct msg_st data; char buffer[BUFSIZ]; int msgid = -1; //建立消息队列 msgid = msgget((key_t)1234, 0666 | IPC_CREAT); if(msgid == -1) { fprintf(stderr, "msgget failed with error: %d\n", errno); exit(EXIT_FAILURE); } //向消息队列中写消息，直到写入end while(running) { //输入数据 printf("Enter some text: "); fgets(buffer, BUFSIZ, stdin); data.msg_type = 1; //注意2 strcpy(data.text, buffer); //向队列发送数据 if(msgsnd(msgid, (void*)&data, MAX_TEXT, 0) == -1) { fprintf(stderr, "msgsnd failed\n"); exit(EXIT_FAILURE); } //输入end结束输入 if(strncmp(buffer, "end", 3) == 0) running = 0; sleep(1); } exit(EXIT_SUCCESS); }
? jiangtf ./send Enter some text: abs You wrote: abs Enter some text: tjdf You wrote: tjdf Enter some text: end You wrote: end [1] + 59241 done ./a.out
? jiangtf ./send
Enter some text: asd
Enter some text: intad
Enter some text: end
消息队列与命名管道的区别
在命名管道中，发送数据用write，接收数据用read，则在消息队列中，发送数据用msgsnd，接收数据用msgrcv。而且它们对每个数据都有一个最大长度的限制。与命名管道相比，消息队列的优势在于：
1、消息队列也可以独立于发送和接收进程而存在，从而消除了在同步命名管道的打开和关闭时可能产生的困难。
2、同时通过发送消息还可以避免命名管道的同步和阻塞问题，不需要由进程自己来提供同步方法。
3、接收程序可以通过消息类型有选择地接收数据，而不是 像命名管道中那样，只能默认地接收。
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原文地址：http://www.cnblogs.com/jeakeven/p/5063877.html
