Problems running program using Runtime.exec()

Question

Hello everyone. I have a quick problem that perhaps someone can help me with... I'm trying to write a frontend for a command line program. I've found plenty of examples for using exec() to launch this program but I can't quite get the effect that I desire. The program itself launches it's own window (using a graphics library called SDL) but the user interacts with the program through the command prompt.
The problem that I'm having is that my InputStream thread does not seem to execute until I close the SDL window. I've tried about 10 different combinations of threading this application but nothing seems to work.
Below I've attached some sample code that I found here on the Sun site... The code does as I described before, the InputStream does not display any text until I close the SDL window.
Can anyone help out?
import java.io.*;
// class StreamGobbler omitted for brevity
class StreamGobbler extends Thread
InputStream is;
String type;
OutputStream os;
StreamGobbler(InputStream is, String type)
this(is, type, null);
StreamGobbler(InputStream is, String type, OutputStream redirect)
this.is = is;
this.type = type;
this.os = redirect;
public void run()
try
PrintWriter pw = null;
if (os != null)
pw = new PrintWriter(os);
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line=null;
while ( (line = br.readLine()) != null)
if (pw != null)
pw.println(line);
System.out.println(type + ">" + line);
if (pw != null)
pw.flush();
} catch (IOException ioe)
ioe.printStackTrace();
public class TestExec
public static void main(String args[])
if (args.length < 1)
System.out.println("USAGE: java TestExec \"cmd\"");
System.exit(1);
try
String cmd = args[0];
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec(cmd);
// any error message?
StreamGobbler errorGobbler = new
StreamGobbler(proc.getErrorStream(), "ERR");
// any output?
StreamGobbler outputGobbler = new
StreamGobbler(proc.getInputStream(), "OUT");
// kick them off
errorGobbler.start();
outputGobbler.start();
// any error???
int exitVal = proc.waitFor();
System.out.println("ExitValue: " + exitVal);
} catch (Throwable t)
t.printStackTrace();

Answer 1

I'm pretty sure, because if you run the application without any parameters you don't get the SDL window, you just get a list of possible command line switches, that part works fine... It just seems that when the SDL window is open, the thread won't grab and display the individual lines until that window is closed, which will not work for my purposes...