xref: /freebsd/stand/lua/hook.lua.8 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

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.\" Copyright (c) 2018 Kyle Evans <kevans@FreeBSD.org>
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.Dd April 28, 2020
.Dt HOOK.LUA 8
.Os
.Sh NAME
.Nm hook.lua
.Nd FreeBSD hook module
.Sh DESCRIPTION
.Nm
contains functionality for defining hook types and attaching hooks.
Hooks are functions used to attach custom behaviors at pre-defined points in
loader execution.
These pre-defined points are what we refer to as
.Dq hook types .
Hooks may also take an optional data parameter, which may or may not be
populated by the caller.
.Pp
Before using the functionality provided by
.Nm ,
it must be included with a statement such as the following:
.Pp
.Dl local hook = require("hook")
.Ss Exported functions
The following functions are exported from
.Nm :
.Bl -tag -width hook.registerType -offset indent
.It Fn hook.registerType hooktype
Adds
.Ev hooktype
as a recognized hook type.
This allows functions to be added to run when hooks of this type are invoked
using
.Fn hook.runAll hooktype .
.It Fn hook.register hooktype hookfunc
Register
.Ev hookfunc
to be run when hooks of type
.Ev hooktype
are invoked.
.It Fn hook.runAll hooktype
Invoke all hooks registered for type
.Ev hooktype .
Hooks are invoked in the order in which they are registered.
.El
.Ss Hook Naming Guidelines
Hook names should consist of the name of the module they are defined in, as well
as a verb describing when the hook is executed, separated by a period.
For example,
.Dq config.reloaded
is defined in the
.Xr config.lua 8
module and run when the configuration is reloaded.
.Sh EXAMPLES
To register a hook to be run when configuration is reloaded:
.Pp
.Bd -literal -offset indent -compact
local hook = require("hook")

local function configuration_was_reloaded()
	print("Configuration was reloaded!")
end

hook.register("config.reloaded", configuration_was_reloaded)
.Ed
.Sh AUTHORS
The
.Nm
file was originally written by
.An Kyle Evans Aq Mt kevans@FreeBSD.org .