#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/msg.h>
 
int main(int argc, char *argv[]){
	int ipc_key,msg_id,msg_len;
	long mtype;
	void * mbuf;
	if(argc==5 && argv[3][0]=='s'){
		ipc_key=atoi(argv[1]);
		mtype=atol(argv[2]);
		msg_len=strlen(argv[4]);
		if ( 0>(msg_id=msgget(ipc_key, 0666|IPC_CREAT)))return 1;
		if ( NULL==(mbuf=malloc(msg_len+sizeof(long)+1)) )return 2;
		memcpy(mbuf, (void *)&mtype, sizeof(long) );
		memcpy(mbuf+sizeof(long), (void *)argv[4], msg_len );
		if ( 0>msgsnd(msg_id, (struct msgbuf *)mbuf, msg_len, 0) )return 3;
		printf("Send Success.n");
	}else if(argc==4 && argv[3][0]=='r'){
		ipc_key=atoi(argv[1]);
		mtype=atol(argv[2]);
		if ( 0>(msg_id=msgget(ipc_key, 0666)))return 1;
		if ( NULL==(mbuf=malloc(4096)) )return 2;
		if ( 0>(msg_len=msgrcv(msg_id,(struct msgbuf *)mbuf, 4000, mtype, IPC_NOWAIT))){
			printf("No message received.n");
			return 3;
		}
		printf("Recv Success.(%d bytes):n",msg_len);
		printf("%sn",(char *)(mbuf+sizeof(long)));
	}else if(argc==3 && argv[2][0]=='c'){
		ipc_key=atoi(argv[1]);
		if ( 0>(msg_id=msgget(ipc_key, 0666)))return 1;
		if ( 0>msgctl(msg_id,IPC_RMID,(struct msqid_ds *)mbuf) )return 2;
	}else{
		printf("usage:"
			"%s key type s message --to send messagen"
			"%s key type r --to receiven"
			"%s key c --to clear queuen"
			,argv[0],argv[0],argv[0]);
	}
	return 0;
}

$ gcc -o ipc_msg ipc_msg.c
#编译
$ ipcs -q
 
------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages    
#一开始系统中没有消息队列。
$ ./ipc_msg  1 2 s abc
Send Success.
#发送了一个内容为abc的消息
$ ipcs -q
 
------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages    
0x00000001 262144     lily       666        3            1           
#发送了一个消息以后，队列里有消息了，key是1,有3个字节。
$ ./ipc_msg  1 2 r
Recv Success.(3 bytes):
abc
#从消息队列成功收到消息了。
$ ipcs -q
 
------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages    
0x00000001 262144     lily       666        0            0           
#收完以后，空的消息队列仍然存在，不会自动消失。
 
$ ./ipc_msg  1 c
#删除队列
$ ipcs -q
 
------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages    
#成功删除了，回到原始状态。

sum([n for n in range(1000) if n%3==0 or n%5==0])