os.pullEvent
 Function os.pullEvent | |
| Waits (yields) until an event occurs, and returns details about that event before removing it from the event queue. If a "filter" is specified, it will wait until an event matching that type is found in the queue - any events that enter the queue before that one are also removed, so take care not to "discard" ones you don't need! Be aware that many other functions (most any that "pause" or "wait" for any amount of time) make use of os.pullEvent(). For example, calling sleep() will start a timer, then wait for a timer event to occur. If any other events happen before that timer event enters the queue (notably, those generated by rednet messages sent to the computer), they'll be discarded. In many cases use of the Parallel API functions offers a simple way around this, but if you need to listen for multiple event types at once it's generally best to forgo the filter and use if/then statements to respond according to what event type you get. If Ctrl+T is held, a terminate event will be generated - if os.pullEvent() (or by extension, any function that uses it) spots this in the queue it will exit your script. This is not the case with the near-identical os.pullEventRaw(). See also: os.pullEventRaw() | |
| Syntax | os.pullEvent([string filter]) |
| Returns | string event, any param1, param2, ... (see table below) |
| Part of | ComputerCraft |
| API | OS |
Examples
 Example | |
| The program requires to wait for a keypress to do something: | |
| Code |
while true do print( "Press E to do something." ) local event, key = os.pullEvent( "key" ) -- limit os.pullEvent to the 'key' event if key == keys.e then -- if the key pressed was 'e' print( "You pressed [E]. Exiting program..." ) break end end |
Additional Notes
- When you press a key on the keyboard that is a printable character ("A", "]", etc...) "char" and "key" events are both fired, commonly the "key" event is first fired and after it "char" event is fired.
Common syntax
local event, param1, param2, param3 = os.pullEvent()
Note: This is one of the most commonly used functions that can return multiple values. It works like any other function call (such as "local input = read()") except that you can get more than one piece of information back.
How it works
When os.pullEvent() is called, the computer waits until an event occurs. Events can be triggered by several different things, such as a key being pressed or a redstone input changing. They are usually triggered by ComputerCraft itself, when it needs to notify the computer that something happened. They can also be triggered by peripherals, or by your program calling os.queueEvent.
More complicated input, such as "the user typing a line of text," does not correspond to any one single event. read handles this inside itself by waiting for the user to press a key, then updating the screen, moving the cursor, etc.
Events have a type (which is a string) and 0-5 parameters (which are often but not always strings). No built-in events use more than 5 parameters.
When an event occurs, the event type, followed by the parameters, will be returned. If you have:
local event, button, x, y = os.pullEvent()
and the user clicks the mouse at coordinates 5,4 then:
- event will be set to "mouse_click" (the event type)
- button will be set to 0 (the first parameter)
- x will be set to 5 (the second parameter)
- y will be set to 4 (the third parameter)
Note that in this example, we didn't specify a filter. If you specify a filter, then all events of different types will be ignored. If the user inserts a disk, instead of clicking the mouse, then event will be "disk", button will be the side the disk drive is on, and x and y will be nil.
If we wanted to only wait for mouse clicks we could use:
local event, button, x, y = os.pullEvent("mouse_click")
which will ignore any events that are not mouse clicks.
If you assign more variables than necessary, the extra ones will be set to nil. If you assign fewer variables than necessary, the extra parameters will be discarded.
Event types
| Name | Description | Parameters | ||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | ||
| char | Fired when text is typed on the keyboard | string the letter typed | ||||
| key | Fired when a key is pressed on the keyboard | number numerical keycode | boolean is being held | |||
| key_up | Fired when a key is released | number numerical keycode | ||||
| paste | Fired when Ctrl + V is pressed on the keyboard | string system clipboard text | ||||
| timer | Fired when a timeout started by os.startTimer() completes | number Value of the timer as returned by os.startTimer() | ||||
| alarm | Fired when a time passed to os.setAlarm() is reached | number Value of the alarm as returned by os.setAlarm() | ||||
| task_complete | Fired when an asynchronous task completes. Used by every commands API method internally which yields, including commands.execAsync(), but excluding commands.getBlockPosition(). Also used internally by every command block's method. | number taskID | boolean success | [string error] | any param1, param2, ... | |
| redstone | Fired when the state of any of the redstone inputs change | |||||
| terminate | Fired when a combination of keys CTRL and T is pressed and held for three seconds.
You will not normally see this event, as it is handled inside os.pullEvent. |
|||||
| disk | Fired when a disk is inserted into an adjacent disk drive | string side | ||||
| disk_eject | Fired when a disk is removed from an adjacent disk drive | string side | ||||
| peripheral | Fired when peripheral is attached | string side | ||||
| peripheral_detach | Fired when peripheral is removed | string side | ||||
| rednet_message | Fired when a rednet message is received from the rednet API | number senderID | any message | string protocol / number distance travelled | ||
| modem_message | Fired when a modem message is received from the modem | string side | number frequency | number replyFrequency | any message | number distance travelled |
| http_success | Fired when an attempt to receive text from / post text on a website is successful.
You will not normally see this event as it is handled inside http.get. |
string url of the site | table text on the site | |||
| http_failure | Fired when an attempt to receive text from / post text on a website is unsuccessful
You will not normally see this event as it is handled inside http.get. |
string url of the site | ||||
| mouse_click | Fired when a mouse button is pressed | number mouse button | number x coordinate | number y coordinate | ||
| mouse_up | Fired when a mouse button is released | number mouse button | number x coordinate | number y coordinate | ||
| mouse_scroll | Fired when a mousewheel is scrolled. | number scroll direction (-1 for up, 1 for down) | number x coordinate(in screen chars) | number y coordinate(in screen chars) | ||
| mouse_drag | Fired when the mouse is moved after clicking. | number mouse button | number x coordinate(in screen chars) | number y coordinate(in screen chars) | ||
| monitor_touch | Fired when a player right clicks on a connected advanced monitor. | string side | number x coordinate(in screen chars) | number y coordinate(in screen chars) | ||
| monitor_resize | Fired when a connected monitor resizes. | string side | ||||
| term_resize | Fired when the terminal resizes. | |||||
| turtle_inventory | Fired when the inventory on a Turtle is changed. | |||||
