@Override
          public void onLine(String line) {
            synchronized (Interactive.this) {
              if (command == null) {
                return;
              }

              String contentPart = line;

              int markerIndex = line.indexOf(command.marker);
              if (markerIndex == 0) {
                contentPart = null;
              } else if (markerIndex > 0) {
                contentPart = line.substring(0, markerIndex);
              }

              if (contentPart != null) {
                if (wantSTDERR)
                  addBuffer(contentPart);
                processLine(contentPart, onStderrLineListener);
              }

              if (markerIndex >= 0) {
                lastMarkerStderr = command.marker;
                processMarker();
              }
            }
          }
Internal call that launches the shell, starts gobbling, and starts executing commands. See
{@link Shell.Interactive}

@return Opened successfully ?
imitate/src/main/java/com/engineer/imitate/shell/Shell.java