Windows Batch Variables Won't Set

Question

I think I ran into a bug in Window's batch scripting.

I cannot set variables that are in an expanded if statement.

Here is an isolated part of my script:

@echo off

set success=1
set Version=12345
set Target=Client
set Type=456
set dir=
set zip=

if "%Version%"=="" set success=0
if "%Type%"=="" set success=0

if 1==1 set test=42

if %success%==1 (
    set test2=57005
    if "%Target%"=="Client" (
        set dir=ModName v%Version%
        set zip=ModName v%Version% %Type%.zip
        echo Version: %Version%
        echo    Type: %Type%
        echo.
        echo  Target: %Target%
        echo     dir: %dir%
        echo     zip: %zip%
        echo.
        echo    test: %test%
        echo   test2: %test2%
    )
) else (
    echo Not successful.
)

This is the output from a brand new instance of cmd:

C:\Users\RandomClown\Desktop>test.bat
Version: 12345
   Type: 456

 Target: Client
    dir:
    zip:

   test: 42
  test2:

What you should notice is that the single line if statement correctly sets stuff. The multiline if will perform anything that is NOT a set. I dont think I missed anything. Also, the multiline if statement is correctly executing the right lines, as the else ( echo Not successful. ) lines did not execute.

Why did the lines not execute?

Solution

You missed something ;-)

cmd expands variables when commands are parsed, not when they are run. It so happens that an if or for statement with a block ( ... ) (or actually any block) counts as a single command in that case. So when you set variables inside a block and try using them in the same block there are no variables anymore – they were replaced by the values the variables had before the block even executed.

Stick a

setlocal enabledelayedexpansion

at the start of your batch file and use !zip! instead of %zip%. See help set for a detailed discussion of the problem.

Comments

[Brent Rittenhouse]

the "set" command doesn't always take every string after the equals sign. Example: set one=1 & echo Hiya. Good point about the parenthesis though, they are indeed super helpful.