Batch script error: "/ was unexpected at this time." - batch-file

Question

I wrote a little script to display every line of a text file with a random amount of pause between each of them:
SET pauseTime=10
SET maxval=20
SET minval=5
FOR /f %%j in (search1.txt) DO (
SET pauseTime=%RANDOM% * (%maxval% - %minval% + 1) / 32768 + %minval%
ECHO.%pauseTime%
TIMEOUT %pauseTime%
ECHO.%%j
)
Running this in cmd.exe gives me:
C:\Users\Tim\Desktop>SET minval=5
/ was unexpected at this time.
However, if I simply do:
FOR /f %%j in (search1.txt) DO (
ECHO.%%j
)
I get all the lines printed with no errors
What's going on?

Answer 1

You need to add the /A switch to your SET statement in order to do math operations. (I usually also have to remove any embedded spaces to get it to work properly as well.)
SET /A pausetime=%RANDOM%*(%maxval%)-%minval%)/32768+%minval%
The error you're getting is also caused by the batch processor not properly handing the parentheses within the for expression (the nested pair in the numeric expression). You can fix that by breaking that part of the expression out to a separate variable, and then using that variable in place of the portion within the parentheses:
SET pauseTime=10
SET maxval=20
SET minval=5
SET /A maxmin=%maxval% - %minval% + 1
FOR /f %%j in (search1.txt) DO (
SET /A pauseTime=%RANDOM% * %maxmin% / 32768 + %minval%
ECHO. %pauseTime%
TIMEOUT %pauseTime%
ECHO. %j%
)

Answer 2

the issue here is because you use nested ( ) brackets which batch can't handle and causes your issue, you might need to split your pausetime calculation into 2 lines.
see this article
The CMD shell statement does not use any great intelligence when evaluating parenthesis, so for example the command below will fail:
IF EXIST MyFile.txt (ECHO Some(more)Potatoes)

Answer 3

As mentioned within the other answers, the problem is caused by the nested parenthesis.
Instead of avoiding them, you could also escape them by preceding ^ characters -- this works:
IF EXIST MyFile.txt (ECHO Some^(More^)Potatoes)
Without the caret ^ here, the command line interpreter takes the first ) to close the first (.
However, applying the above escape technique to the code of the original question avoids the error message, but does not result in a working script, even if the inner SET is replaced by SET /a (as mentioned by #KenWhite), because you need to establish delayed environment variable expansion; otherwise, the displayed pauseTime value is always the initial one, 10. The following fix works:
#ECHO OFF
SET pauseTime=10
SET maxval=20
SET minval=5
SETLOCAL EnableDelayedExpansion
FOR /f %%j in (search1.txt) DO (
SET /a pauseTime=!RANDOM!*^(maxval-minval+1^)/32768+minval
ECHO.!pauseTime!
TIMEOUT !pauseTime!
ECHO.%%j
)
ENDLOCAL
Herein, the SETLOCAL statement enables the delayed expansion before the FOR command executes. In the body of the FOR loop, %pauseTime% and %RANDOM% are replaced by !pauseTime! and !RANDOM!, respectively; those are the variables subject to delayed expansion (because of the enclosing !!), meaning that they are not (as usual) expanded immediately when the entire FOR command is parsed, but when it is executed. For the sake of legibility, I removed the %% from the other variables in the SET /a command since they are not required when the /a switch is present (note that there is also a % operator supported!!).
Note: After this script has run, pauseTime is reset to the initial value 10 as the SETLOCAL/ENDLOCAL block constitutes a new localised environment namespace; if you need the last value, replace line ENDLOCAL by ENDLOCAL & SET pauseTime=%pauseTime%; this utilises standard immediate expansion...
Nevertheless, since minval and maxval are constants in the script it is most intelligent to do the calculation maxval-minval+1 outside of FOR once only, like #KenWhite suggested.