From the NannyMUD documentation

LAST CHANGE

2001-09-29

NAME

        whod - A who daemon

DESCRIPTION

	This daemon keeps track on whom is logged, linkdead or not. It
	also generates some of the text files shown on the WWW
	pages. It can also be used to make some NPC's to appear as
	real players. The main use from a wizards point of view would
	be to get call-backs to certain objects when players, or a
	named player, logs on and off. 

FUNCTIONS

OTHER FUNCTIONS

	There are basically two useful functions available for your
	use:

	add_callback
	add_named_callback

	The other functions in this object should not be used; the
	nifty ones might appear in /obj/support.c any year now.

NOTE

	If someone updates this object, players might log on from LD
	and be able to look at their own statues, full of equipment.
	Don't update this object. 

FUNCTION

NAME
        add_callback - Add callbacks to an object.


SYNTAX
void add_callback(object where)

DESCRIPTION
	1/ When a player enters the game, the function
	   'login_callback' is called in the object 'where' with the
	   player object as the first argument, and the player name as
	   the second.

	2/ When a player exits the game, the function
	   'logout_callback' is called in the object 'where' with the
	   player object as the first argument, and the player name as
	   the second.




FUNCTION

NAME
        add_named_callback - Callback based on name.


SYNTAX
void add_named_callback(string name, object where, mixed data)

DESCRIPTION
	This builds a list of objects that wishes to get a callback
	when the named player enters/exits the game. The functions
	called in the object 'where' are 'login_callback' and
	'logout_callback', with three arguments: the player object,
	the name and the data.


NOTE
	The callback is removed from the list when it has been used.