Path Handler scripts are defined in the Custom Files configuration file.

These scripts get executed when the file or files (when using wildcards) are requested to load by the game.

These scripts can either redirect the file to a different path altogether or create a new file on the fly using Output or UseCallbacks. This has a number of applications including but not limited to dynamically creating mission scripts with random elements or elements based on mod settings.

Example

This is an example PathHandler definition and the script for it from Donut Mod 4.

[PathHandler]
art\\frontend\\scrooby\\resource\\pure3d\\homer.p3d=Resources/scripts/handlers/mainmenuskins.lua

When homer.p3d is requested, the script redirects it to one of the files in the MainMenuSkins at random.

-- Table of main menu skin paths.
MainMenuSkins = {
	GetModPath() .. "/Resources/art/mainmenuskins/h_work.p3d",
	GetModPath() .. "/Resources/art/mainmenuskins/h_pieman.p3d",
	GetModPath() .. "/Resources/art/mainmenuskins/h_sshield.p3d",
}

-- Redirect to one of them at random.
Redirect(MainMenuSkins[math.random(1, #MainMenuSkins)])