Help with Runtime class and timeout of Process

Question

Hi,
Question regarding using Runtime class, and yes I have looked at the javadocs, but I am still confused and frustrated.
Here is part of my code.
Process p;
Runtime runtime = Runtime.getRuntime();
p = runtime.exec("rsh localhost ls");
if you are not familiar with rsh all it does is remote shell into the computer localhost and executes the command ls.
Now, I dont have rsh running on my computer so it will hang at that line for about 40 sec and eventually time out on its own. Is there anyway I can specify a timeout argument like there is for the ping command? Like if there is no response from localhost after 3 sec, then just kill the process?
I looked at the Runtime javadoc and Process javadoc and the closest thing I could come to with is something to do with envp (environment parameters), but I dont know what that is.
Thanks guys.

Answer 1

You can't timeout the "runtime.exec("rsh localhost ls");" call but if you execute the call in a seperate thread you can "timeout" and continue executing on the original thread (while letting the "runtime" thread to timeout on its own).
Check the following class that I created for cases like this:
abstract public class TimeoutHelper implements Runnable
    private Throwable error;
    private boolean running = true;
    private Object retValue;
    protected String name;
    private long waitTime;
    private Thread thread;
     * Creates a new helper. Use {@link #start} to run the code.
     * @param name A name that will be used in the helper thread name
     * @param waitTime The time (in msec) to wait before timeout.
    public TimeoutHelper(String name, long waitTime)
        this.name = name;
        this.waitTime = waitTime;
    public Object start() throws Throwable
        return asyncExecute();
    abstract protected Object execute() throws Throwable;
    private synchronized Object asyncExecute() throws Throwable
        createThread().start();
        if (running)
            try
                wait(waitTime);
                if (running)
                    // Timeout!!
                    abortThread();
                    throw new TimeOutException("Timeout for: " + name);
            catch (InterruptedException ie)
                // Ignore
        if (error != null)
            throw error;
        return retValue;
    private void abortThread()
        if (thread != null)
            thread.interrupt();
    protected Thread createThread()
        thread = new Thread(this, name);
        return thread;
    public void run()
        try
            retValue = execute();
        catch (Throwable th)
            error = th;
        synchronized (this)
            running = false;
            notifyAll();
}You use the class by extending it and implementing "execute". For example:
        TimeoutHelper helper = new TimeoutHelper("Runner", 5000)
            protected Object execute() throws Throwable
                Runtime runtime = Runtime.getRuntime();
                return runtime.exec("rsh localhost ls");
        try
            Process p = (Process)helper.start();
        catch (TimeOutException e)
            // Handle timeout here
        catch (Exception e)
            // Handle other errors here.
        }