DOS返回ErrorLevel沒有運行程序

Question

我通過DOS提示符運行Powershell命令，我想在開始運行我的命令之前檢查是否安裝了Powershell。如果沒有顯示下面的實際錯誤，powershell不存在，我希望腳本退出。這裏是我的腳本：

@echo off 
setlocal enabledelayedexpansion 
:: Check to see if Powershell is installed 
powershell.exe -command {"test"} > NUL 
if errorlevel 1 (
    echo/Powershell is NOT Installed 
    EXIT 
) else (
    goto PSI 
) 

:PSI 
powershell Set-ExecutionPolicy RemoteSigned 

說我有問題是，我得到這個作爲輸出：

Powershell is NOT Installed 

'powershell.exe' is not recognized as an internal or external command, 
operable program or batch file. 

Answer 1

想通了！我不得不使用2> NUL代替NUL重定向輸出：

:: Check to See if Powershell is Installed 
powershell.exe test 2>NUL 
    if errorlevel 1 (
     echo/Powershell is NOT Installed 
    EXIT 
    ) else (
    goto PSI 
    )