[java] ProcessBuilder: Forwarding stdout and stderr of started processes without blocking the main thread

It's as simple as following:

    File logFile = new File(...);
    ProcessBuilder pb = new ProcessBuilder()
        .command("somecommand", "arg1", "arg2")
    processBuilder.redirectErrorStream(true);
    processBuilder.redirectOutput(logFile);

by .redirectErrorStream(true) you tell process to merge error and output stream and then by .redirectOutput(file) you redirect merged output to a file.

Update:

I did manage to do this as follows:

public static void main(String[] args) {
    // Async part
    Runnable r = () -> {
        ProcessBuilder pb = new ProcessBuilder().command("...");
        // Merge System.err and System.out
        pb.redirectErrorStream(true);
        // Inherit System.out as redirect output stream
        pb.redirectOutput(ProcessBuilder.Redirect.INHERIT);
        try {
            pb.start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    };
    new Thread(r, "asyncOut").start();
    // here goes your main part
}

Now you're able to see both outputs from main and asyncOut threads in System.out