Access denied using XP_CMDSHELL

Question

Hi, I tried to create a TXT file from SQL SERVER 2012 using "XP_CMDSHELL" but i got a msg "Access Denied"

 

Something like this:

 

DECLARE @cmd sysname, @var sysname;

SET @var = 'Hello world';

SET @cmd = 'echo ' + @var + ' > var_out.txt';

EXEC master..xp_cmdshell @cmd;

 

what´s could be wrong??