问题如题，结果如图，
linux 下 gnuplot 用了 set ylabel "yname"为什么没有显示 y 轴 yname？

gnuplot> set term dumb
Terminal type set to 'dumb'
Options are 'feed  size 79, 24'
gnuplot> set title "sin(x)"
gnuplot> set xlabel "xname"
gnuplot> set ylabel "yname"
gnuplot> plot sin(x)


                                     sin(x)

    1 ++---------------***---------------+---**-----------+--------***----++
      +                *  *              +  *  **         +  sin(x) ****** +
  0.8 ++              *    *                *    *               *    *   ++
  0.6 ++             *      *              *     *               *     *  ++
      *              *      *             *      *               *      *  |
  0.4 +*             *      *             *       *             *       * ++
      |*            *        *            *        *           *        *  |
  0.2 +*           *         *            *        *           *        * ++
    0 ++*          *          *          *         *          *          *++
      | *          *          *         *           *         *           *|
 -0.2 ++ *         *          *         *           *         *           *+
      |  *        *            *       *             *       *            *|
 -0.4 ++ *       *             *       *             *       *            *+
      |   *      *              *      *             *      *              *
 -0.6 ++  *     *               *     *               *     *             ++
 -0.8 ++   *    *               *    *                *    *              ++
      +     *  *       +         **  *   +             *  *                +
   -1 ++----***--------+-----------**----+--------------***---------------++
     -10              -5                 0                5                10
                                      xname