#!/bin/bash
read -p "input number1 and number2:" num1 num2   #-p后面跟提示信息
a=$num1
b=$num2
[ -z "$a" ]&&{
 echo "is input a"
 exit 1
 }
[ -z "$b" ]&&{
 echo "is input b"
 exit 1
 }
expr $a + $b + 1 &>/dev/null    #判断是否是整数
[ $? -ne 0 ]&&{
 echo "input a b is int"
 exit 2
 }
echo "$a - $b = $(($a - $b))"    
if [ "$b" = "0" ];then
 echo "b is no 0"
 else
 echo "$a / $b = $(($a / $b))"
fi