How to expand a CMD shell variable twice (recursively)

Question

Using the Windows XP CMD command-line I can expand a variable twice as follows:

set AAA=BBB
set BBB=CCC
for /F \"usebackq tokens=*\" %i in (`echo %%AAA%%`) d         


        

Answer 1

The following (torturous) approach seems to work okay:

    @echo off
:main
    setlocal enableextensions enabledelayedexpansion
    set aaa=bbb
    set bbb=ccc
    call :myset x %%aaa%%
    echo %x%
    endlocal
    goto :eof
:myset
    for /F "usebackq tokens=*" %%i in (`echo %%%2%%`) do set %1=%%i
    goto :eof

It outputs:

ccc

as desired.

I've often used that trick to (for example) format %aaa% into %x% to a certain size (a la sprintf) but this is the first time I've had to do double indirection. It works because you don't find the extra "%%" being sucked up by the current shell level.