Batch script skipping blank entries in a .CSV when delim is ','

Question

I have a .CSV that I am trying to sort through to create another file from the data, but when I run it through, it skips blank entries. For example, if a line is valu

Answer 1

This is the standard behaviour of the FOR/F loop, consecutive delims only used as one delimiter.
But you can use a workaround with a second FOR/F.
Prefix each column with another character, split the line at the delim and remove the prefix.

setlocal EnableDelayedExpansion
FOR /F "delims=" %%L in (test.bat) DO (
    set "line=%%L,,,,,,,,"
    set "line=#!line:,=,#!"
    FOR /F "tokens=1,2,3,4 delims=," %%a in ("!line!") DO (
        set "param1=%%a"
        set "param2=%%b"
        set "param3=%%c"
        set "param4=%%d"
        set "param1=!param1:~1!"
        set "param2=!param2:~1!"
        set "param3=!param3:~1!"
        set "param4=!param4:~1!"
        echo !param1! !param2! !param3! !param4!
    )
)

Answer 2

As jeb already mentiones in his answer, for /F treats consecutive delimiters as one. To avoid that, you could replace each delimiter , by "," and enclose each full line by "", so each field appears as being enclosed within "", which can easily be removed finally by the ~ modifier of the for /F variable; so there is no need to do any more string manipulations (like sub-string expansion) later on:

@echo off
setlocal EnableExtensions DisableDelayedExpansion
for /F "usebackq delims=" %%# in ("file.csv") do (
    set "LINE=%%#"
    setlocal EnableDelayedExpansion
    for /F "tokens=1-4 delims=," %%A in (^""!LINE:,="^,"!"^") do (
        endlocal
        echo Field 1: %%~A
        echo Field 2: %%~B
        echo Field 3: %%~C
        echo Field 4: %%~D
        setlocal EnableDelayedExpansion
    )
    endlocal
)
endlocal

This might not work properly if the data contain , characters by themselves (remember that , is not considered as delimiter in case a field is enclosed within "" in the original CSV file).

The toggling of delayed expansion is done to not lose any exclamation marks in the data.