SQL Server Service: environment variables

if you want to know which environment variables the SQL Server service  “knows”, you can check it this way:
DECLARE @VarName varchar(300) = ”
DECLARE @env varchar(8000)
SET NOCOUNT ON
SET @env = ‘set ‘ + @VarName
CREATE TABLE #env (outputData varchar(8000))
INSERT INTO #env EXEC master..xp_cmdshell @env
SELECT * from #env
DROP TABLE #env