Displaying a shell from within a Java program

Question

Hi,
For some long and twisted reason, I need to execute native programs from a Java program. Since this program is only every intended to be run on Linux, this doesn't bother me breaking the x-platform rules for Java! So, Runtime.exec() is the normal way to do this.
However, Runtime.exec() runs executes the command and then dishes basck the output once it's finished. The external program I wish to run takes a while and actually prints various pieces of feedback during its processing. I'd like to display this feedback to the user as it happens, rather than dumping it all at the end.
I can't think of anyway to do this. I've been looking for "Java shells" but they are reimplemented shells with only let you run classes on the classpath. Any ideas from the gurus around here?
Cheers

Answer 1

import java.util.*;
import java.io.*;
class StreamGobbler extends Thread
InputStream is;
String type;
StreamGobbler(InputStream is, String type)
this.is = is;
this.type = type;
public void run()
try
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line=null;
while ( (line = br.readLine()) != null)
System.out.println(type + "> " + line);
} catch (IOException ioe)
ioe.printStackTrace();
public class GoodLinuxExec
public static void main(String args[])
if (args.length < 1)
System.out.println("USAGE: java GoodLinuxExec <cmd>");
System.exit(1);
try
Runtime rt = Runtime.getRuntime();
System.out.println("Execing " + args[0]);
Process proc = rt.exec(args);
// any error message?
StreamGobbler errorGobbler = new
StreamGobbler(proc.getErrorStream(), "ERROR");
// any output?
StreamGobbler outputGobbler = new
StreamGobbler(proc.getInputStream(), "OUTPUT");
// kick them off
errorGobbler.start();
outputGobbler.start();
// any error???
int exitVal = proc.waitFor();
System.out.println("ExitValue: " + exitVal);
} catch (Throwable t)
t.printStackTrace();
stolen from this article and adapted to suit an os which does not start with the letter W.