How do I route the output from an external process to the output window?

Apache NetBeans Wiki Index

Note: These pages are being reviewed.

NetBeans 6.8 and up: Use the External Execution API. Implement a Callable which will actually start the process:

private class ProcessLaunch implements Callable<Process> {
  private final String[] commandLine;
  public ProcessLaunch(String... commandLine) {
    this.commandLine = commandLine;
  public Process call() throws Exception {
    ProcessBuilder pb = new ProcessBuilder(cmdline); File(System.getProperty("user.home"))); //NOI18N
    return pb.start();

Create an ExecutionDescriptor:

ExecutionDescriptor descriptor = new ExecutionDescriptor().controllable(true).frontWindow(true).
  preExecution(new SomeRunnableToCallBeforeStart()).postExecution(new SomeRunnableToCallAfterExit());

The before and after runnables can be used to, say, update the user interface when the process starts and stops.

Then actually launch your process. Standard output and standard error (if you leave in the call to redirectErrorStream(true) above) output will be redirected to the output window, and the tab name in the Output Window will be what you specify below. The variable theCommandLineArguments is an array of strings, just as you would pass to Runtime.exec() - the command-line to run whatever program you want to run.

ExecutionService exeService = ExecutionService.newService(
  new ProcessLaunch(theCommandLineArguments),
  descriptor, "My Process");
Future<Integer> exitCode =;

(you can use the returned Future to wait for the process to exit and get its exit code - just don’t do that in the Swing event thread).

Applies to: NetBeans 6.8 and up.

What about processes using the System.out/System.err?

Sometimes we are using a third party package that we don’t have access to its source or we don’t want to modify.

In this case you just need to redirect the system streams like this:

private void redirectSystemStreams() {
        out = new OutputStream() {

            public void write(int i) throws IOException {
                OutputHandler.output(outputName, String.valueOf((char) i));

            public void write(byte[] bytes) throws IOException {
                OutputHandler.output(outputName, new String(bytes));

            public void write(byte[] bytes, int off, int len) throws IOException {
                OutputHandler.output(outputName, new String(bytes, off, len));
        System.setOut(new PrintStream(out, true));
        System.setErr(new PrintStream(out, true));

OutputHandler is just a helper class that I’ve been using for a while. Feel free to use it. You need to add a dependency to I/O APIs package even if you don’t use it to avoid run time issues. If you don’t use it replace the OutputHandler calls for something like this:

IOProvider.getDefault().getIO(name, false).getOut().println(mess);

The OutputHandler referenced above has been transformed into a plugin for easier use. See here for more details.