batch file fails to set variable in IF clause

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" ) )

paxdiablo · Accepted Answer · 2009-12-30 02:47:04Z

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.

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