急！！如何画立方体的那几根斜线在shell脚本下

如何画立方体的那几根斜线在shell脚本下
下面是四边形4条边的画法，类似这种格式画立方体的斜线....


52 count=1 画垂直线
53 for (( r=$1; count<=$BOX_HEIGHT; r++)); do
54 plot_char $r $2 $VERT
55 let count=count+1
56 done
57
58 count=1
59 c=`expr $2 + $BOX_WIDTH`
60 for (( r=$1; count<=$BOX_HEIGHT; r++)); do
61 plot_char $r $c $VERT
62 let count=count+1
63 done
64
65 count=1 画水平线
66 for (( c=$2; count<=$BOX_WIDTH; c++)); do
67 plot_char $1 $c $HORZ
68 let count=count+1
69 done
70
71 count=1
72 r=`expr $1 + $BOX_HEIGHT`
73 for (( c=$2; count<=$BOX_WIDTH; c++)); do
74 plot_char $r $c $HORZ
75 let count=count+1
76 done




122 clear
123 R=15
124 C=15
125 H=20
126 W=40
127 col=1
draw_box $R $C $H $W $col