计算：判断如果不是数字，则不继续运行方法

                  read 读入和整数判断方法                        

#!/bin/bash
while true;do
        read -p "Num1 Num2:" num1 num2
        expr $num1 + 0 &>/dev/null
        [ $? -ne 0 ]&& continue
        expr $num2 + 0 &>/dev/null
        [ $? -ne 0 ]&& continue || break  #break如果是整数，则结束这个循环；
done
echo "num1-num2 =$(( $num1 - $num2 ))"
echo "num1+num2 =$(( $num1 + $num2 ))"
echo "num1*num2 =$(( $num1 * $num2 ))"
echo "num1/num2 =$(( $num1 / $num2 ))"
echo "num1**num2 =$(( $num1 ** $num2 ))"
echo "num1%num2 =$(( $num1 % $num2 ))"

增加对传入参数的判断：

#!/bin/bash
num1="$1"
num2="$2"

if [ $# -ne 2 ];then
        echo "arge error."
        exit 1
fi
expr $num1 + 0 &>/dev/null
[ $? -ne 0 ]&& exit
expr $num2 + 0 &>/dev/null
[ $? -ne 0 ]&& exit
echo "num1-num2 =$(( $num1 - $num2 ))"
echo "num1+num2 =$(( $num1 + $num2 ))"
echo "num1*num2 =$(( $num1 * $num2 ))"
echo "num1/num2 =$(( $num1 / $num2 ))"
echo "num1**num2 =$(( $num1 ** $num2 ))"
echo "num1%num2 =$(( $num1 % $num2 ))"