#!/usr/bin/env bash

calc(){
  PS3="choose the oper: "
  select oper in + - \* / # 生成操作符选择菜单
  do
  echo -n "enter first num: " && read x # 读取输入参数
  echo -n "enter second num: " && read y # 读取输入参数
  exec
  case ${oper} in
    "+")
      return $((${x} + ${y}))
    ;;
    "-")
      return $((${x} - ${y}))
    ;;
    "*")
      return $((${x} * ${y}))
    ;;
    "/")
      return $((${x} / ${y}))
    ;;
    *)
      echo "${oper} is not support!"
      return 0
    ;;
  esac
  break
  done
}
calc
echo "the result is: $?" # $? 获取 calc 函数返回值
#  $ ./function-demo.sh
#  1) +
#  2) -
#  3) *
#  4) /
#  choose the oper: 3
#  enter first num: 10
#  enter second num: 10
#  the result is: 100
