# Working with rules and scripts
Now that we have the two items - "Presence_Mobile_John" aka "Johns mobile" and "Wallplug_FF_LR_TV" aka "TV wallplug LR" - we can create a simple rule. Let's assume we want to turn on the wallplug (and give some juice to the connected TV) as soon as John's mobile comes online, turn it off again when the mobile goes offline (this would be a very basic "presence" rule).
Rules are defined in the $OPENHAB_CONF/rules directory.
So we create the file default.rules there.
$OPENHAB_CONF/rules/default.rules
You can create as many .rules files as you want - this eases the overview of different rules/situations. For example:
- presence.rules for the presence detection
- alarm.rules for your alarm actions
- tv.rules for rules specific for your SmartTV
- and so on
For now, we edit the default.rules
rule "Wallplug_FF_LR_TV ON"
when
Item Presence_Mobile_John changed from OFF to ON
then
Wallplug_FF_LR_TV.sendCommand(ON)
end
rule "Wallplug_FF_LR_TV OFF"
when
Item Presence_Mobile_John changed from ON to OFF
then
Wallplug_FF_LR_TV.sendCommand(OFF)
end
The rule syntax in this example is very easy:
rule "rule name (should be unique for logging purposes)"
when
<TRIGGER CONDITION1> or
<TRIGGER_CONDITION2> or
<TRIGGER_CONDITION3>
...
then
<EXECUTION_BLOCK>
end
The trigger conditions can be one of the following:
- Item triggers - just like in the example above. If the state of an item changes, do something
- Time triggers - do something at a specified time
- System triggers - do something after a system event happened, i.e. openHAB was started or is shut down
More information on rules can be found in the rules section of the user manual!
The execution block in the example only consists of the "sendCommand" command, which sets the state of the named item.
ItemName.sendCommand(STATE)
Once the mobile comes online, the wallplug will turn on, As soon as it goes offline, it will turn off. Just as simple as that 😃
This part has to be completed!
Guidelines
I think this will become the longest section
Don't forget to address JSR233 or other alternatives to the DSL that will be built into openHAB
Event driven development
Format and structure of rules
Difference between actions and posting sending things to items
Functions
Group.members manipulation and how it can help simplify your rules
How to figure out what to import
Working with Time
Working with Timers
Casting to appropriate types and when that is necessary
Working with Numbers
Working with States
Lambdas -> in advanced openHAB
...