Shell脚本计算器

1）交互式输入三个值 num1 flag num2

2）当且仅当，num1==0 and num2==0 退出

3）针对flag的符号进行运算，输出运算结果

4)如果flag,不是这些运算符.输出error flag,继续步骤1

#!/bin/bash
while [ "0" == "0" ]
do
read -p "num1: " num1
read -p "flag: " flag
read -p "num2: " num2

if [ "$num1" == "0" ] && [ "$num2" == "0" ]; then
break
fi

case $flag in
"+")
sum=$(($num1+$num2))
;;
"-")
sum=$(($num1-$num2))
;;
"*")
sum=$(($num1*$num2))
;;
"/")
sum=$(($num1/$num2))
;;
*)
echo "Wrong flag!"
;;
esac
echo "$num1 $flag $num2 = $sum"
done
echo "END!"
exit 0