linux-tutorial/codes/shell/demos/function/function-demo.sh

#!/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