Difference between revisions of "Os.pullEvent"

From ComputerCraft Wiki
Jump to: navigation, search
m (Added an example of os.pullEvent as a function iterator in for loops)
(→‎Event types: Updated to ComputerCraft 1.74)
 
(19 intermediate revisions by 9 users not shown)
Line 2: Line 2:
 
{{Function
 
{{Function
 
  |name=os.pullEvent
 
  |name=os.pullEvent
−
  |args=[{{type|string}} filter]
+
  |args=[<nowiki></nowiki>{{type|string}} filter]
 
  |api=OS
 
  |api=OS
−
  |returns={{type|string}} event, variable parameters(see table below)
+
  |returns={{type|string}} event, {{type|any}} param1, param2, ... (see table below)
 
  |addon=ComputerCraft
 
  |addon=ComputerCraft
−
  |desc=Waits (yields) until an event occurs
+
  |desc=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!<br><br>
 +
 
 +
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 [[Os.sleep|sleep()]] will [[os.startTimer|start a timer]], then wait for a [[timer_(event)|timer event]] to occur. If any other events happen before that timer event enters the queue (notably, those generated by [[Rednet (API)|rednet messages]] sent to the computer), they'll be discarded. In many cases use of the [[Parallel (API)|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.<br><br>
 +
 
 +
If Ctrl+T is held, a [[terminate (event)|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|os.pullEventRaw()]].<br><br>
 +
 
 +
[[#How it works|See below]] for more detailed information on the command.<br><br>See also: [[os.pullEventRaw|os.pullEventRaw()]]
 
  |examples=
 
  |examples=
 
{{Example
 
{{Example
 
|desc=The program requires to wait for a keypress to do something:
 
|desc=The program requires to wait for a keypress to do something:
−
|code=[[Function (type)|function]] clear()
+
|code=
−
    [[term.clear]]()
+
−
    [[term.setCursorPos]] (1,1)
+
−
end
+
 
  while true do
 
  while true do
−
    clear()
+
  [[print]]( "Press E to do something." )
−
    [[print]] ("Press E to do something.")
+
 
−
    local event, param1 = os.pullEvent ("char") -- limit os.pullEvent to the char event
+
  local event, key = '''os.pullEvent( "key" )''' -- limit os.pullEvent to the [[Key_(event)|'key']] event
−
    if param1 == "e" then -- if the returned value was 'e'
+
 
−
        clear()
+
  if key == [[Keys_(API)|keys]].e then -- if the key pressed was 'e'
−
        [[write]] ("Name: ")
+
    [[print]]( "You pressed [E]. Exiting program..." )
−
        local name = [[read]]()
+
    break
−
        [[print]] (name)
+
  end
−
        break
+
−
    else
+
−
        clear()
+
−
        [[print]] ("Wrong button!")
+
−
        [[os.sleep|sleep]] (1.5) -- I don't like a whole 2 seconds but 1 second is too short
+
−
    end
+
 
  end
 
  end
 
}}
 
}}
−
{{Example
+
|notes=* When you press a key on the keyboard that is a printable character ("''A''", "'']''", etc...) [[char_(event)|"char"]] and [[key_(event)|"key"]] events are both fired, commonly the "key" event is first fired and after it "char" event is fired.
−
|desc=This script shows how the os.pullEvent function can be used as an iterator instead of using a while loop:
+
−
|code=for event, param1 in os.pullEvent do --this will continuously fire an event without the use of a while loop
+
−
    [[print]]("Event: "..event)
+
−
    [[print]]("Param1: "..param1)
+
−
end
+
−
[[User:SuicidalSTDz|SuicidalSTDz]] 20:23, 29 March 2013 (MSK)
+
−
}}
+
 
}}
 
}}
  
−
=== Common syntax ===
+
__TOC__
 +
 
 +
== Common syntax ==
  
−
  event, param1, param2, param3 = os.pullEvent()
+
  local event, param1, param2, param3 = '''os.pullEvent()'''
  
 
Note: This is one of the most commonly used functions that can return multiple values.
 
Note: This is one of the most commonly used functions that can return multiple values.
−
It works like any other function call (such as "input = read()") except that you can get more than one piece of information back.
+
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 ==
 
== How it works ==
Line 54: Line 46:
 
They can also be triggered by peripherals, or by your program calling [[os.queueEvent]].
 
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 an event.
+
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.
 
[[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).
 
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 3 parameters.
+
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:
 
When an event occurs, the event type, followed by the parameters, will be returned. If you have:
  
−
  event, button, x, y = os.pullEvent()
+
  local event, button, x, y = '''os.pullEvent()'''
  
 
and the user clicks the mouse at coordinates 5,4 then:
 
and the user clicks the mouse at coordinates 5,4 then:
Line 75: Line 67:
 
If we wanted to only wait for mouse clicks we could use:
 
If we wanted to only wait for mouse clicks we could use:
  
−
   event, button, x, y = os.pullEvent("mouse_click")
+
   local event, button, x, y = '''os.pullEvent("mouse_click")'''
  
 
which will ignore any events that are not mouse clicks.
 
which will ignore any events that are not mouse clicks.
Line 86: Line 78:
 
! rowspan="2" | Name
 
! rowspan="2" | Name
 
! rowspan="2" | Description
 
! rowspan="2" | Description
−
! colspan="3" | Parameters
+
! colspan="5" | Parameters
 
|-
 
|-
−
! 1 !! 2 !! 3
+
! 1 !! 2 !! 3 !! 4 !! 5
 
|-
 
|-
 
! scope="row" | [[char (event)|char]]
 
! scope="row" | [[char (event)|char]]
 
|Fired when text is typed on the keyboard
 
|Fired when text is typed on the keyboard
 
| {{type|string}} the letter typed
 
| {{type|string}} the letter typed
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 99: Line 93:
 
|Fired when a key is pressed on the keyboard
 
|Fired when a key is pressed on the keyboard
 
|{{type|number}} numerical keycode
 
|{{type|number}} numerical keycode
 +
|{{type|boolean}} is being held
 +
|
 +
|
 +
|
 +
|-
 +
! scope="row" | [[key_up (event)|key_up]]
 +
|Fired when a key is released
 +
|{{type|number}} numerical keycode
 +
|
 +
|
 +
|
 +
|
 +
|-
 +
! scope="row" | [[paste (event)|paste]]
 +
|Fired when Ctrl + V is pressed on the keyboard
 +
|{{type|string}} system clipboard text
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 105: Line 117:
 
|Fired when a timeout started by [[os.startTimer]]() completes
 
|Fired when a timeout started by [[os.startTimer]]() completes
 
|{{type|number}} Value of the timer as returned by os.startTimer()
 
|{{type|number}} Value of the timer as returned by os.startTimer()
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 112: Line 126:
 
|{{type|number}} Value of the alarm as returned by os.setAlarm()
 
|{{type|number}} Value of the alarm as returned by os.setAlarm()
 
|
 
|
 +
|
 +
|
 +
|
 +
|-
 +
! scope="row" | [[task_complete_(event)|task_complete]]
 +
|Fired when an asynchronous task completes. Used by every [[commands_(API)|commands API]] method internally which yields, including [[commands.execAsync]](), but excluding [[commands.getBlockPosition]](). Also used internally by every [[Command_Block_(API)|command block's method]].
 +
|{{type|number}} taskID
 +
|{{type|boolean}} success
 +
|[<nowiki/>{{type|string}} error]
 +
|{{type|any}} param1, param2, ...
 
|
 
|
 
|-
 
|-
 
! scope="row" | [[redstone (event)|redstone]]
 
! scope="row" | [[redstone (event)|redstone]]
 
|Fired when the state of any of the redstone inputs change
 
|Fired when the state of any of the redstone inputs change
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 123: Line 149:
 
|Fired when a combination of keys CTRL and T is pressed and held for three seconds.
 
|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.
 
You will not normally see this event, as it is handled inside os.pullEvent.
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 130: Line 158:
 
|Fired when a disk is inserted into an adjacent disk drive
 
|Fired when a disk is inserted into an adjacent disk drive
 
|{{type|string}} side
 
|{{type|string}} side
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 136: Line 166:
 
|Fired when a disk is removed from an adjacent disk drive
 
|Fired when a disk is removed from an adjacent disk drive
 
|{{type|string}} side
 
|{{type|string}} side
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 142: Line 174:
 
|Fired when peripheral is attached
 
|Fired when peripheral is attached
 
|{{type|string}} side
 
|{{type|string}} side
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 148: Line 182:
 
|Fired when peripheral is removed
 
|Fired when peripheral is removed
 
|{{type|string}} side
 
|{{type|string}} side
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 154: Line 190:
 
|Fired when a rednet message is received from the [[Rednet_(API)|rednet API]]
 
|Fired when a rednet message is received from the [[Rednet_(API)|rednet API]]
 
|{{type|number}} senderID
 
|{{type|number}} senderID
−
|{{type|string}} message
+
|{{type|any}} message
 +
|{{type|string}} protocol / {{type|number}} distance travelled
 +
|
 +
|
 +
|-
 +
! scope="row" | [[modem_message (event)|modem_message]]
 +
|Fired when a modem message is received from the [[modem]]
 +
|{{type|string}} side
 +
|{{type|number}} frequency
 +
|{{type|number}} replyFrequency
 +
|{{type|any}} message
 
|{{type|number}} distance travelled
 
|{{type|number}} distance travelled
 
|-
 
|-
Line 162: Line 208:
 
|{{type|string}} url of the site
 
|{{type|string}} url of the site
 
|{{type|table}} text on the site
 
|{{type|table}} text on the site
 +
|
 +
|
 
|
 
|
 
|-
 
|-
Line 168: Line 216:
 
You will not normally see this event as it is handled inside http.get.
 
You will not normally see this event as it is handled inside http.get.
 
|{{type|string}} url of the site
 
|{{type|string}} url of the site
 +
|
 +
|
 
|
 
|
 
|
 
|
Line 176: Line 226:
 
|{{type|number}} x coordinate
 
|{{type|number}} x coordinate
 
|{{type|number}} y coordinate
 
|{{type|number}} y coordinate
 +
|
 +
|
 +
|-
 +
! scope="row" | [[mouse_up (event)|mouse_up]]
 +
|Fired when a mouse button is released
 +
|{{type|number}} mouse button
 +
|{{type|number}} x coordinate
 +
|{{type|number}} y coordinate
 +
|
 +
|
 
|-
 
|-
 
! scope="row" | [[mouse_scroll (event)|mouse_scroll]]
 
! scope="row" | [[mouse_scroll (event)|mouse_scroll]]
Line 182: Line 242:
 
|{{type|number}} x coordinate(in screen chars)
 
|{{type|number}} x coordinate(in screen chars)
 
|{{type|number}} y coordinate(in screen chars)
 
|{{type|number}} y coordinate(in screen chars)
 +
|
 +
|
 
|-
 
|-
 
! scope="row" | [[mouse_drag (event)|mouse_drag]]
 
! scope="row" | [[mouse_drag (event)|mouse_drag]]
Line 188: Line 250:
 
|{{type|number}} x coordinate(in screen chars)
 
|{{type|number}} x coordinate(in screen chars)
 
|{{type|number}} y coordinate(in screen chars)
 
|{{type|number}} y coordinate(in screen chars)
 +
|
 +
|
 
|-
 
|-
 
! scope="row" | [[monitor_touch (event)|monitor_touch]]
 
! scope="row" | [[monitor_touch (event)|monitor_touch]]
−
|Fired when a player right click on an advanced monitor connected.
+
|Fired when a player right clicks on a connected advanced monitor.
 
|{{type|string}} side
 
|{{type|string}} side
 
|{{type|number}} x coordinate(in screen chars)
 
|{{type|number}} x coordinate(in screen chars)
 
|{{type|number}} y coordinate(in screen chars)
 
|{{type|number}} y coordinate(in screen chars)
 +
|
 +
|
 +
|-
 +
! scope="row" | [[monitor_resize (event)|monitor_resize]]
 +
|Fired when a connected monitor resizes.
 +
|{{type|string}} side
 +
|
 +
|
 +
|
 +
|
 +
|-
 +
! scope="row" | [[Term_resize_(event)|term_resize]]
 +
|Fired when the terminal resizes.
 +
|
 +
|
 +
|
 +
|
 +
|
 +
|-
 +
! scope="row" | [[turtle_inventory_(event)|turtle_inventory]]
 +
|Fired when the inventory on a [[Turtle]] is changed.
 +
|
 +
|
 +
|
 +
|
 +
|
 
|}
 
|}
  
 
== Guides ==
 
== Guides ==
−
[http://www.computercraft.info/forums2/index.php?/topic/1516-ospullevent-what-is-it-and-how-is-it-useful/page__view__findpost__p__11156 ''Onionnion's Guide on os.pullEvent()'']
+
* [http://www.computercraft.info/forums2/index.php?/topic/1516-ospullevent-what-is-it-and-how-is-it-useful/page__view__findpost__p__11156 ''Onionnion's Guide on os.pullEvent()'']
 +
* [[Raw key events]]
  
 
[[Category:Lua_Core_Functions]]
 
[[Category:Lua_Core_Functions]]

Latest revision as of 11:53, 28 June 2015


Grid Redstone.png  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 below for more detailed information on the command.

See also: os.pullEventRaw()
Syntax os.pullEvent([string filter])
Returns string event, any param1, param2, ... (see table below)
Part of ComputerCraft
API OS

Examples

Grid paper.png  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.

Guides

Retrieved from "https://www.computercraft.info/wiki/index.php?title=Os.pullEvent&oldid=7073"