Batch file loosing variables in FOR loop

Question

I am struggling with this one for some time now. Tried WITH and WITHOUT EnableDelayedExpansion, but no joy. Simply, the variable %MYFILENAME% is empty right after it's set in a loop:

::echo off
setlocal enabledelayedexpansion
echo -- BACKUP DATABASES --
set MYPATH=D:\SQL_BACKUP
set MYDBASES=db1 db2 db3 db4

For /f "tokens=2-4 delims=/ " %%a in ('date /t') do (set MYDATE=%%c%%a%%b)
For /f "tokens=1-2 delims=/:" %%a in ("%TIME%") do (set MYTIME=%%a-%%b)
set MYDATE=%MYDATE:.=-%

for %%q in (%MYDBASES%) do (
    echo DB %%q processing 
    set MYFILENAME=%MYPATH%\%%q_%MYDATE%_%MYTIME%.bak
    set SERVERNAME=.
    echo %MYFILENAME%
    echo sqlcmd -B -E -S %SERVERNAME% -d master -Q "BACKUP DATABASE [%%q] TO DISK = N'%MYFILENAME%' WITH INIT , NOUNLOAD , NAME = N'%%q backup', NOSKIP , STATS = 10, NOFORMAT"
    if %ERRORLEVEL% == 0 (
        echo OK
    ) else if %ERRORLEVEL% == 1 (
        echo failed!
    )
)

echo.
set MYDATE=
set MYTIME=
set BACKUPFILENAME=
set MYPATH=
set MYDBASES=
set MYFILENAME=

What I get is lost %MYFILENAME% imediatelly:

echo DB db1 processing
 set MYFILENAME=db1_11-11-2016_0-54.bak
 set SERVERNAME=.
 echo <<<----------HERE MISSING MYFILENAME ----------<<<
 echo sqlcmd -B -E -S . -d master -Q "BACKUP DATABASE [zdvrhnika] TO DISK = N''
WITH INIT , NOUNLOAD , NAME = N'zdvrhnika backup', NOSKIP , STATS = 10, NOFORMAT
"

Any idea?

EDIT After changing MYFILENAME and SERVERNAME variables to some simple texts, I found out, that they do not change at all! MYFILENAME is always empty, and SERVERNAME is always ".", regardless of what I set them to?! And regardless of whether I use SETLOCAL EnableDelayedExpansion or not. It's not script fault, but some environment stuff.

Also related: Variable setting exhibits unexpected behavior when set inside for loop. — aschipfl
– aschipfl, Commented Nov 11, 2016 at 2:12

Magoo · Accepted Answer · 2016-11-11 00:07:53Z

1

Within a block statement (a parenthesised series of statements), the entire block is parsed and then executed. Any %var% within the block will be replaced by that variable's value at the time the block is parsed - before the block is executed - the same thing applies to a FOR ... DO (block).

Hence, IF (something) else (somethingelse) will be executed using the values of %variables% at the time the IF is encountered.

Two common ways to overcome this are 1) to use setlocal enabledelayedexpansion **and use !var! in place of %var% to access the changed value of var ** or 2) to call a subroutine to perform further processing using the changed values.

answered Nov 11, 2016 at 0:07

Magoo

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2 Comments

user6811411 Over a year ago

A third way is to use a pseudo call and double the percent signs call echo %%var%% or call set Var=%%OtherVar%%

Labsy Over a year ago

Magoo, excellent! Works like a charm (replacing %variable% with !variable! inside block statements)! Thank you very much!

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