DOWNLOAD_COMMAND="curl -fLSs --retry 5 --retry-delay 1 --retry-connrefused"
      return
    fi
    echo curl does not support https, will try wget for downloading files.
  else
    echo curl is not installed, will try wget for downloading files.
  fi

  # Try wget.
  if command -v wget > /dev/null; then
    DOWNLOAD_COMMAND="wget -qO -"
    return
  fi
  echo wget is not installed.