How to wait on a file to populate?

[ndedhia1]

Hi,
I need help writing code to wait for a file to populate on another machine.
I am doing a cattail on a log file on another machine, and when the file gets written to, then I need to perform some action in my java code, but I need the code to wait till something on the log file does get populated.
Right now, my code seems to fly by the section that has the cattail command and I need for it to stop and wait.

I have tried creating a thread and giving the thread the max priority, but i still can not get the method to wait for my cattail.

The code below shows the class and methods involved that i have written that doesnt work:

public void run()
	{
		try
		{
			System.out.println("YOU ARE IN DESKTOPSHMTRANSLATOR RUN()");
			this.listen();
		}
		catch(Exception e)
		{
			System.out.println("RUN EXCEPTION");
		}
	}
	
	public void listen() throws Exception
	{
		System.out.println("YOU ARE IN DESKTOPSHMTRANSLATOR LISTEN()");
		
		String remoteCommand = "cattail";
		String remoteDir = "/infra/sbt-support/supportTools/hsqldb/ics/tmp/";
		String remoteFile = "alarmNotification.log.orig";
		
		String server = "server";
		String userName = "username";
		String password = "password";
		
		
		StringBuffer rcmd = new StringBuffer();
		rcmd.append(remoteCommand);
		rcmd.append(" ");
		rcmd.append(remoteDir);
		rcmd.append(remoteFile);
		
		System.out.println("RCMD IS: " + rcmd);
		
	
		IgnoreHostKeyVerification hostKey = new IgnoreHostKeyVerification();
        SshClient ssh = new SshClient();
        ssh.connect(server, 22, hostKey);
        //Authenticate
        PasswordAuthenticationClient passwordAuthenticationClient = new PasswordAuthenticationClient();
        passwordAuthenticationClient.setUsername(userName);
        passwordAuthenticationClient.setPassword(password);
        int result = ssh.authenticate(passwordAuthenticationClient);
        if(result != AuthenticationProtocolState.COMPLETE){
                System.out.println("Login to " + server + ":" + " " + userName + "/" + password + " failed");
        }
        
        SessionChannelClient sshChannel = new SessionChannelClient();
        sshChannel = ssh.openSessionChannel();
        sshChannel.executeCommand(rcmd.toString());
        BufferedReader reader = new BufferedReader(new InputStreamReader(sshChannel.getInputStream()));
        System.out.println("READER IS: " + reader.readLine());

		String currentLine;
		
		Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
		System.out.println("PRIOTIRY IS: " + Thread.currentThread().getPriority());
		while((currentLine = reader.readLine()) != null)
		{
			System.out.println("YOU ARE IN LISTEN");
		}
		
		sshChannel.close();
        ssh.disconnect();

	}//listen

Thanks very much for your help!!!

[Dheeraj Joshi]

Why can't you implements lock on the files?
Check this link.
Check this link too.

Regards
Dheeraj Joshi

[ndedhia1]

When and how do i use the filelock? By the time i get to the line

System.out.println("READER IS: " + reader.readLine());

the value is null, which means that my while loop will never be true.

thanks again for the help!!

[ndedhia1]

Hi Dheeraj,
Thanks for your help. I was using the wrong cattail command and once i fixed that, i got it to work.

thanks