UNABLE TO EXECUTE THE CMDSQL SCRIPT IN A STORE PROCEDURE.

I am trying to call a .sql file from sql cmd mode.

The requirement is to pass the .sql file as parameter value to the cmd script which I have able to achieve,here is the code which is working fine .

declare @x sysname
set @x = 'C:\Users\testuser\Desktop\testing.sql'

:OUT $(TEMP)\GetServerName1.sql
PRINT ':SETVAR FilePath'+ ' ' + @x
GO
:OUT stdout

:r $(TEMP)\GetServerName1.sql
GO
:r $(FilePath)

But when I try to wrap this code in store procedure it is giving the message fatal error but when I run it without wrapping it in store proc it is doing its job with no error . When I looked into the store proc I found the code as

ALTER proc [dbo].[testing]
as

declare @x sysname
set @x = 'C:\Users\testuser\Desktop\testing.sql'

PRINT ':SETVAR FilePath'+ ' ' + @x

It seems like the sqlcmd code disappears automatically. I have no clue why it is happening. 

Can anyone help in letting me knw how to wrap the above code in store proc.

Thanks Saurav