使用shell脚本编写一个菱形

#!/bin/bash
read -p "请输入菱形的最大数：" A
for ((i=1;i<=$A;i++))
 do
  for ((k=$A;k>$i;k--))
   do
     echo -n "  "
   done
  for ((j=1;j<=$i;j++))
   do
    echo -n '*   '
   if [ $j = $i ]
    then
     echo -e '\n'  
   fi
   done
 done
for ((a=$A-1;a>=1;a--))
 do
  for ((b=$A;b>$a;b--))
   do
     echo -n "  "
   done
  for ((c=1;c<=$a;c++))
   do
    echo -n '*   '
    if [ $c = $a ]
     then
       echo -e '\n'  
    fi
   done
 done