Enable and Disable Delayed Expansion, what does it do?

Question

I\'ve seen SETLOCAL ENABLEDELAYEDEXPANSION & SETLOCAL DISABLEDELAYEDEXPANSION in many batch files but what do the commands actually do?

Answer 1

With delayed expansion you will able to access a command argument using FOR command tokens:

setlocal enableDelayedExpansion
set /a counter=0
for /l %%x in (1, 1, 9) do (
 set /a counter=!counter!+1
 call echo %%!counter! 
)
endlocal

Can be useful if you are going to parse the arguments with for loops

It helps when accessing variable through variable:

 @Echo Off
 Setlocal EnableDelayedExpansion
 Set _server=frodo
 Set _var=_server
 Set _result=!%_var%!
 Echo %_result%

And can be used when checking if a variable with special symbols is defined:

setlocal enableDelayedExpansion
set "dv==::"
if defined !dv! ( 
   echo has NOT admin permissions
) else (
   echo has admin permissions
)