GRASS GIS: How do I run a batch (bash?) script?

Question

I am in a GRASS database (in command shell), where I want to run a loop function. For example, I want to do an operation on many raster files that are in the database. I know this must be done through a txt file. What i am confused about is where I should put this file, and how exactly I should call it.

I am also a bit confused if I should be writing a batch or a bash file. GRASS is UNIX based which makes me think I should be looking to bash, but I am in windows command shell, where batch scripting applies.

Thanks for your help!