当做出无效选择时让菜单循环 BASH

Question

嘿伙计们，所以我试图让这个菜单在 case 语句中做出无效选择时循环，但很难弄清楚我应该在 while 循环中回调什么，我尝试使用 * ，因为这就是中引用的内容case 作为无效选择，但当它看到它时它需要一个操作数，所以我不确定如何在下面调用它是代码，非常感谢任何帮助。

#Main menu.
#Displays a greeting and waits 8 seconds before clearing the screen

echo "Hello and welcome to the group 97 project we hope you enjoy using our program!"

sleep 8s
clear

while [[ $option -eq "*" ]]
do
    #Displays a list of options for the user to choose.

    echo "Please select one of the folowing options."
    echo -e "\t0. Exit program"
    echo -e "\t1. Find the even multiples of any number."
    echo -e "\t2. Find the terms of any linear sequence given the rule Un=an+b."
    echo -e "\t2. Find the numbers that can be expressed as the product of two nonnegative integers in succession and print  them in increasing order."

    #Reads the option selection from user and checks it against case for what to do.

    read -n 1 option

    case $option in
        0)
            exit ;;
        1)
            echo task1 ;;
        2)
            echo task2 ;;
        3)
            echo task3 ;;
        *)
            clear
            echo "Invalid selection, please try again.";;
    esac
done

Answer 1

select菜单的实现：

#!/usr/bin/env bash

PS3='Please select one of the options: '
select _ in \
  'Exit program' \
  'Find the even multiples of any number.' \
  'Find the terms of any linear sequence given the rule Un=an+b.' \
  'Find the numbers that can be expressed as the product of two nonnegative integers in succession and print them in increasing order.'
do
  case $REPLY in
    1) exit ;;
    2) echo task1 ;;
    3) echo task2 ;;
    4) echo task3 ;;
    *) echo 'Invalid selection, please try again.' ;;
  esac
done