訊息佇列是訊息的連結表，包括Posix訊息佇列system V訊息佇列。有足夠許可權的程序可以向佇列中新增訊息，被賦予讀許可權的程序則可以讀走佇列中的訊息。訊息佇列克服了訊號承載資訊量少，管道只能承載無格式位元組流以及緩衝區大小受限等缺點。下面是兩個測試模組

接收模組

msgreceive.c 的程式碼如下

/*============================================================================= 
#     FileName: msgreceive.c
#         Desc: receice message from message queue 
#       Author: Licaibiao 
#      Version:  
#   LastChange: 2017-01-20
#      History: 
=============================================================================*/

#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[128];
};

int main()
{
	int running = 1;
	int msgid = -1;
	int len = 0;
	long int msgtype = 5; 
	struct msg_st data;
		
	msgid = msgget((key_t)1234, 0666 | IPC_CREAT);
	if(-1 == msgid )
	{
		fprintf(stderr, "msgget failed with error: %d\n", errno);
		exit(EXIT_FAILURE);
	}
	
	while(running)
	{
		memset(&data.text, 0, 128);
		len = msgrcv(msgid, (void*)&data, 128, msgtype, 0);
		if(-1 == len)
		{
			fprintf(stderr, "msgrcv failed with errno: %d\n", errno);
			exit(EXIT_FAILURE);
		}
		printf("You wrote: %s\n",data.text);

		if(0 == strncmp(data.text, "end", 3))
			running = 0;
	}

	//remove message queue
	if(-1 == msgctl(msgid, IPC_RMID, 0))
	{
		fprintf(stderr, "msgctl(IPC_RMID) failed\n");
		exit(EXIT_FAILURE);
	}
	exit(EXIT_SUCCESS);
}
 

傳送模組

/*=============================================================================
#     FileName: msgsend.c
#         Desc: send data to message queue
#       Author: Licaibiao
#      Version: 
#   LastChange: 2017-01-20 
#      History:
=============================================================================*/

#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;
	int len;

	msgid = msgget((key_t)1234, 0666 | IPC_CREAT);
	if(msgid == -1)
	{
		fprintf(stderr, "msgget failed with error: %d\n", errno);
		exit(EXIT_FAILURE);
	}

	while(running)
	{
		
		printf("Enter data : ");
		fgets(buffer, BUFSIZ, stdin);
		data.msg_type = 5;    
		strcpy(data.text, buffer);
	    len = strlen(data.text);	
		if(msgsnd(msgid, (void*)&data, len-1, 0) == -1)
		{
			fprintf(stderr, "msgsnd failed\n");
			exit(EXIT_FAILURE);
		}
		
		if(strncmp(buffer, "end", 3) == 0)
			running = 0;
		usleep(100000);
	}
	exit(EXIT_SUCCESS);
}
 

編譯執行結果如下：

[email protected]:/home/test/msg_test# gcc msgsend.c  -o send 
[email protected]:/home/test/msg_test# gcc msgreceive.c -o recv 
[email protected]:/home/test/msg_test# ./recv &
[1] 106594
[email protected]:/home/ysj000/quanzhiSDK/F25_test/test/msg_test# ./send 
Enter data : hello
You wrote: hello
Enter data : test
You wrote: test
Enter data : hello world
You wrote: hello world
Enter data : end
You wrote: end
[1]+  Done                    ./recv
 
[email protected]:/home/test/msg_test# 

與命名管道相比，訊息佇列的優勢在於：

1、訊息佇列也可以獨立於傳送和接收程序而存在，從而消除了在同步命名管道的開啟和關閉時可能產生的困難。

2、同時通過傳送訊息還可以避免命名管道的同步和阻塞問題，不需要由程序自己來提供同步方法。

3、接收程式可以通過訊息型別有選擇地接收資料，而不是像命名管道中那樣，只能預設地接收。