使用Shell写加减乘除计算器

#!/bin/sh

read -p "输入一个数字 : " num1

if [ -n "$num1" ]
then
    test=`echo $num1 | sed 's/[0-9]//g'`
        if [ -z "$test" ]
        then
	    read -p "输入第二个数字 : " num2
	        if [ -n "$num2" ]
		then
		    test2=`echo $num2 | sed 's/[0-9]//g'`
			if [ -z "$test2" ]
			then
			    read -p '输入(+|-|*|/) : ' ope
				case $ope in
				'+')
				    jia=$(( $num1 + $num2 ))
				    echo "$num1 $ope $num2 = $jia "
				    ;;
				'-')
				    jian=$(( $num1 - $num2 ))
				    echo "$num1 $ope $num2 = $jian "
				    ;;
				'*')
				    cheng=$(( $num1 * $num2 ))
				    echo "$num1 $ope $num2 = $cheng "
				    ;;
				'/')
				    chu=$(( $num1 / $num2 ))
				    echo "$num1 $ope $num2 = $chu "
				    ;;
				*)
				    echo "请不要输入除加减乘除外其他的符号"
				esac
			else
			    echo "请不要输入除数字外的内容"

			fi	
		else
		    echo "请输入内容"
		fi
	else
	    echo "请不要输入除数字外的内容"
	fi
else
	echo "请输入内容"
fi