shell 简单计算器

#!/bin/bash

function tool_menu()
{
    echo "****************************************************"
    echo "*                                                  *"
    echo "*              calculation  tools                  *"
    echo "*                                                  *"
    echo "****************************************************"
}
function menu_choice()
{
    echo "A: Add two num."
    echo "B: Minus two num."
    echo "C: Multiply two num."
    echo "D：Divide two num."
    echo "Q: Close this function."
    echo "Please input your chiose:"
}
function add_num()
{
    echo "please inut your first num:"
    read first_num
    echo "please inut your second num:"
    read second_num
    let add=$first_num+$second_num
    echo "$first_num+$second_num=$add"
    return 0
}
function minus_num()
{
    echo "please inut your first num:"
    read first_num
    echo "please inut your second num:"
    read second_num
    let minus=$first_num-$second_num
    echo "$first_num-$second_num=$minus"
    return 0
}
function multiply_num()
{
    echo "please inut your first num:"
    read first_num
    echo "please inut your second num:"
    read second_num
    let multiply=$first_num*$second_num
    echo "$first_num*$second_num=$multiply"
    return 0
}

function divide_num()
{
    echo "please inut your first num:"
    read first_num
    echo "please inut your second num:"
    read second_num
    let divide=$first_num/$second_num
    echo "$first_num/$second_num=$divide"
    return 0
}
function main()
{
    clear
    tool_menu
    while :
    do
        menu_choice
        read menu_choice
        case $menu_choice in
            A|a) add_num ;;
            B|b) minus_num ;;
            C|c) multiply_num ;;
            D|d) divide_num ;;
            Q|q) break;;
            *) echo "Input error,please try agin.";;
        esac
    done
}
main
exit 0

 模板
#!/bin/bash

function tool_menu()
{
    echo "****************************************************"
    echo "*                                                  *"
    echo "*              calculation  tools                  *"
    echo "*                                                  *"
    echo "****************************************************"
}
function menu_choice()
{
    echo "A: Add two num."
    echo "B: Minus two num."
    echo "C: Multiply two num."
    echo "D：Divide two num."
    echo "Q: Close this function."
    echo "Please input your chiose:"
}
function add_num()
{

    echo "add."
}
function minus_num()
{

    echo "minus."
}
function multiply_num()
{
    echo "multiply."

}

function divide_num()
{

    echo "divide."

}
function main()
{
    clear 模板

    tool_menu
    while :
    do
        menu_choice
        read menu_choice
        case $menu_choice in
            A|a) add_num ;;
            B|b) minus_num ;;
            C|c) multiply_num ;;
            D|d) divide_num ;;
            Q|q) break;;
            *) echo "Input error,please try agin.";;
        esac
    done
}
main
exit 0