batch file fails to set variable in IF clause - variables

Question

The following code is not updating Run to equal N even though the match occurs. this means I'm not dropping into the CALL code. Am i missing something here?
SET Run=Y
REM Check current files date/time information and establish if the file has been present too long in the directory
REM Skip first 4 lines as header information not required
FOR /f "tokens=1-5 skip=4 delims= " %%G IN ('dir /OD "%SRCH_CRITERIA% "') DO (
ECHO "Params to processFile: " %%G %%H %%I ""%%K""
IF %%K.==. (
ECHO "K:nothing"
SET Run=N
ECHO %Run%
)
IF %%K==free (
ECHO "K:FREE"
SET Run=N
ECHO %Run%
)
ECHO %Run% RUN
IF %Run%=="Y" (
CALL :processFile "%%G" "%%H" "%%I" "%%K"
)
)

Answer 1

You need to use the delayed expansion option of cmd.exe.
At the top of your script, put:
setlocal enableextensions enabledelayedexpansion
and then put:
endlocal
at the bottom.
Then you need to use !Run! instead of %Run%.
The reason your code is not working is that the entire FOR statement (including the commands within it) is evaluated when it's encountered. That's the point where the %Run% variables are expanded.
By using deferred expansion, you don't expand them until they're actually needed (after you've set them within the block).
You can see the difference in this script:
#echo off
setlocal enableextensions enabledelayedexpansion
set xx=0
for %%i in (a b c d) do (
echo %%i
set /a "xx = xx + 1"
if %xx%==3 echo yes for normal
if !xx!==3 echo yes for delayed
)
endlocal
which outputs:
a
b
c
yes for delayed
d
You'll notice that the check with %xx% does not work because that was evaluated when the for statement started (and xx was 0). The delayed-expansion !xx! does work since that is evaluated each time through the loop.