Windows Batch script - For /L not working -- simple - windows

Question

need some quick help. This is a university program, everything is working fine except when I call my :forLoop method to iterate through 100 numbers (1,1,100) starting at 1 going by 1 til 100 and doing the iteration % 5 (i%%5). for some reason I cannot get this to work. appreciate any help or direction.
When I echo %%A it is iterating through all the number perfect. When I echo %result% I get a blank "" (nothing inside)
:forLoop
FOR /L %%A IN (1,1,100) DO (
set /A result=%%A %% 2
echo "%%A"
echo "%result%"
)
Correct code is
:forLoop
setlocal ENABLEDELAYEDEXPANSION
FOR /L %%A IN (1,1,100) DO (
set /A result=%%A %% 5
echo !result! >> results.txt
set /A total=!total!+!result!
echo !total!
)

Answer 1

The problem is that the %result% is substituted when the for is read, meaning that it is no longer a variable when the loop is executed. What you need is delayed variable expansion to be enabled and then use ! instead of %:
setlocal ENABLEDELAYEDEXPANSION
:forLoop
FOR /L %%A IN (1,1,100) DO (
set /A result=%%A %% 5
echo "%%A"
echo !result!
)
This is all explained in the help message you get when you run SET /?:
Delayed environment variable expansion is useful for getting around
the limitations of the current expansion which happens when a line
of text is read, not when it is executed. The following example
demonstrates the problem with immediate variable expansion:
set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "%VAR%" == "after" #echo If you see this, it worked
)
would never display the message, since the %VAR% in BOTH IF statements
is substituted when the first IF statement is read, since it logically
includes the body of the IF, which is a compound statement. So the
IF inside the compound statement is really comparing "before" with
"after" which will never be equal. Similarly, the following example
will not work as expected:
set LIST=
for %i in (*) do set LIST=%LIST% %i
echo %LIST%
in that it will NOT build up a list of files in the current directory,
but instead will just set the LIST variable to the last file found.
Again, this is because the %LIST% is expanded just once when the
FOR statement is read, and at that time the LIST variable is empty.
So the actual FOR loop we are executing is:
for %i in (*) do set LIST= %i
which just keeps setting LIST to the last file found.
Delayed environment variable expansion allows you to use a different
character (the exclamation mark) to expand environment variables at
execution time. If delayed variable expansion is enabled, the above
examples could be written as follows to work as intended:
set VAR=before
if "%VAR%" == "before" (
set VAR=after
if "!VAR!" == "after" #echo If you see this, it worked
)
set LIST=
for %i in (*) do set LIST=!LIST! %i
echo %LIST%