ProcessBuilder redirected to standard output

Question

I would like to redirect a java process output towards the standard output of the parent java process.

Using the ProcessBuilder class as follows:

public static void main(String[] args) {
  ProcessBuilder processBuilder = new ProcessBuilder("cmd");
  processBuilder.directory(new File("C:"));   
  processBuilder.redirectErrorStream(true); // redirect error stream to output stream
  processBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
}

I would have expected that the outputs of "cmd", which are like:

Microsoft Windows [version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. Tous droits réservés.

are displayed in the DOS console used to run the java program. But nothing is displayed at all in the DOS Console.

In the other threads of discussions, I saw solutions using a BufferedReader class: but here I would like the outputs of the process to be directly displayed in the standard output, without using any BufferedReader or "while reading loop". Is it possible?

Thanks.

Answer 1

You did miss a key piece, you actually need to start your process and wait for your output. I believe this will work,

processBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
// Start the process.
try {
  Process p = processBuilder.start();
  // wait for termination.
  p.waitFor();
} catch (IOException e) {
  e.printStackTrace();
} catch (InterruptedException e) {
  e.printStackTrace();
}

Answer 2

Try ProcessBuilder.inheritIO() to use the same I/O as the current Java process. Plus you can daisy chain the methods:

ProcessBuilder pb = new ProcessBuilder("cmd")
    .inheritIO()
    .directory(new File("C:"));
pb.start();