title: RID permalink: /RID/
Most scripting commands and functions will want to request data about a character, store variables referenced to that character, send stuff to the client connected to that specific character. Whenever a script is invoked by a character, it is passed a so-called RID - this is the account ID number of a character that caused the code to execute by clicking on it, walking into it's OnTouch zone, or otherwise.
When writing simple NPCs only, this topic will not require much attention. However, when using functions, timers, or clock-based script activation, one requires to be aware of all cases when a script execution can be triggered without a RID attached. This will make a lot of commands and functions unusable, since they request data from a specific character, send data to a specific client, or store variables specific to a character, which are unavailable, if there's no RID, which refers to the character to work with, unless attachrid is used to explicitly attach a character to the script first.
Whenever is stated invoking character or currently attached character, it actually means the character whose RID is currently attached to the running script. The script function playerattached can be used to check which is the currently attached player to the script (it will return 0 if the there is no player attached or the attached player no longer is logged on to the map-server). The function detachrid will explicitly set the RID to 0, so care must be taken, that follow-up commands do not depend on a character being attached, especially access to temporary character variables.