Devilspie2 is based on the excellent program Devil's Pie by Ross Burton, and takes a folder as indata, and checks that folder for LUA scripts. These scripts are run each time a window is opened, and the rules in them are applied on the window.
Unfortunately the rules of the original Devils Pie are not supported.
If you don't give devilspie2 any folder with --folder, it will read LUA scripts from the folder that it gets from the GLib function g_get_user_config_dir - this returns the config directory as defined in the XDG Base Directory Specification. In most cases would be the ~/.config/devilspie2/ folder, and this folder will be created if it doesn't already exist. This folder is changeable with the --folder option. If devilspie2 doesn't find any LUA files in the folder, it will stop execution.
Devilspie2 takes some options:
A simple script example can look like this: