Monday, November 27, 2006 8:51 AM bart

Answers to quiz - Batch Scripting Mysteries

A few days ago, I posted this little quiz on batch scripting mysteries. The batch script given was:

@echo off
for %%f in (a,b,c) do (
   echo 1 %%f 2
   set x=x1 %%f x2
   echo %x%
)

Here's the output:

C:\temp>test
1 a 2
ECHO is off.
1 b 2
ECHO is off.
1 c 2
ECHO is off.

C:\temp>test
1 a 2
x1 c x2
1 b 2
x1 c x2
1 c 2
x1 c x2

Not what you might have expected :-). I did some research but HELP SET didn't give the complete answer, so a workaround seems a good solution:

@echo off
for %%f in (a,b,c) do (
   echo 1 %%f 2  
   call :print %%f
)
goto eof

:print
set x=x1 %1 x2
echo %x%

:eof

And of course Windows PowerShell helps us out too:

PS C:\Users\Bart> ('a','b','c') | foreach { echo "1 $_ 2"; $x = "x1 $_ x2"; echo $x }
1 a 2
x1 a x2
1 b 2
x1 b x2
1 c 2
x1 c x2

Yet another reason to choose Windows PowerShell? (Notice the variable expansion in strings too.)

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Comments

# re: Answers to quiz - Batch Scripting Mysteries

Saturday, December 02, 2006 12:33 PM by denis bider

If you want to get this working in cmd.exe without the workaround, run cmd with /v:on to enable delayed environment expansion, and use !x! instead of %x% in the body of the 'for'.