code: public static void consumeProcessOutput(Process self, Appendable output, Appendable error) {
          consumeProcessOutputStream(self, output);
          consumeProcessErrorStream(self, error);
      }
docs: Gets the output and error streams from a process and reads them
  to keep the process from blocking due to a full output buffer.
  The processed stream data is appended to the supplied Appendable.
  For this, two Threads are started, so this method will return immediately.
  The threads will not be join()ed, even if waitFor() is called. To wait
  for the output to be fully consumed call waitForProcessOutput().
  
  @param self a Process
  @param output an Appendable to capture the process stdout
  @param error an Appendable to capture the process stderr
  @since 1.7.5