I wanna know what would be the best way to make a user list.. Would it be ini, txt, other ?

I am scripting a small bot so to speak to allow people auto ops auto voice, the ability to get invited into a chan amungst other options.. cause well I dont want to pay for a shell, and I have a machine on a highspeed line that has a good uptime that rarely ever goes down.. So I am using that as my shell/bot