如何返回如果输入不等于;批处理文件

Question

我一直都在做一个批处理文件来执行程序

@echo off 
:top 
set /p choice=" My Choice = " 
if %choice%=="install program.alpha" goto alpha 
if %choice%=="install program.beta" goto beta 
:alpha 
start="Destination...." 
goto top 
:beta 
start="Destination...." 
goto top 

所以我的问题是。我不能创建一个条件，当用户输入错误的命令，所以它必须返回一个错误。比如用户输入的命令：

install program.gamma 

或

install program.alhfdzbd or something else that not matches the custom commands 

我能做些什么???

Answer 1

如果用户既不输入install program.alpha也不输入install program.beta，只要将输入视为无效。

@echo off 
:top 
set /p choice=" My Choice = " 
if "%choice%"=="install program.alpha" goto alpha 
if "%choice%"=="install program.beta" goto beta 

:: If you get here, the user has typed something wrong. 
echo Invalid selection. Exiting. 
exit /b 

:alpha 
set start="Destination...." 
goto top 
:beta 
set start="Destination...." 
goto top