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:

Answer 1

Just a remind, the ms-dos "set" command takes every string after the equal sign. So if you write

if "x"=="x" set a=foo else set a=bar
echo %a%  // output : foo else set a=bar

The %a% is actually set to "foo else set a=bar", not foo. So I always use "()" for set command if there are multiple commands in one line.

if "%1"=="" (set a=20) else (set a=%1)    

Answer 2

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) counds 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.