Here I made a program in batch that detects all files with the .user extension. Then it allows the user to pick a username by entering the number associated with that username.

The code is messy, so I will explain.

@echo off
setlocal ENABLEEXTENSIONS ENABLEDELAYEDEXPANSION
:login_menu
cls
set x=1
set users=
cd "users"
for %%A in (*.user) do (
echo !x!. %%~nA
set users=%%~nA:!x!,!users!
set /a x=!x!+1
)
echo.
set /p ch=Select User: 
if "%ch%" == "" (goto login_menu)

for %%B in (%users%) do (
    for /f "tokens=1,2 delims=:" %%C in ("%%B") do (
    set userNumber=%%D 
    set userN=%%C
    if !ch! == %%D goto password
    echo BDEV: %%B
    pause
)
)
echo.
echo That user doesn't exist!
pause
goto login_menu

:password
cls
cd "users"
for /f "tokens=1,2 delims=:" %%E in (!userN!.user) do (set password=%%F)
echo Enter your password, !userN!
echo.
set /p password1=Password: 

if %password1% == %password% goto menu
echo.
echo That password is invalid!
pause
goto password

:menu
echo Hey! You're logged in as !userN!
pause

The variable x is going to be the number which the username will be associated with. The variable users Makes sort of a 'map' to usernames to the number associated with that username

In the first for loop, it gets all the files in the folder users. It echo's out all the usernames that the user can pick.

The second for loop goes into the variable users and separates the usernames with their respective numbers. For example: if I have the usernames admin:4,steve:3,john:2,jane:1 it will separate them into admin:4 and steve:3 and john:2 and jane:1.

The third for loop (which is in the second for loop) separates each username to number into separate variables. For example, if we have the username Collins with the number 3, it will put the username Collins in the userN variable and the number 3 into the variable userNumber.

It then checks what number the user selected.

The final for loop goes into the user file that the user has selected. So if the user selected admin it will go to the user file admin.user and find the password.

If the password is invalid, it rejects access. If it correct it allows access.

Is there any way to make it less like spaghetti code?

If you need more explanation, I will be happy to provide more information.