#include <iostream>
#include <assert.h>
#include <sys/types.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <errno.h>
#include <pwd.h>
#include <sys/wait.h>

int main (int argc,char* argv[]) 
{
	//printf("we have %d param, they are %s %s %s %s.\n", argc, argv[0], argv[1], argv[2], argv[3]);	
	if (argc != 4)
	{
		printf("Memory system's cleaner cannot run.\r\n");
		exit(1);
	}
	// the first will be my program name
	// second will be the main process id
	// third will be queue number
	// forth will be the msg file path
	setpgrp();
	int nExit = 0;
	int nMainPid = atoi(argv[1]);
	int nMsgQueue = atoi(argv[2]);
	while(!nExit)
	{
		//向被監視進程發送0信號，以探測其生存狀態
		int nRtn = kill(nMainPid , 0);
		
		if (nRtn != 0)
		{//如果被監視進程已經不存在，則試圖刪除消息隊列和文件標識，并退出
			msgctl( nMsgQueue, IPC_RMID, NULL ); // delete the message queue
			unlink( argv[3] );
			nExit = 1;
		}
		else
		{
			sleep(1);
		}
		
	}
	
	return 0;
}