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