System API documentation

Version: stable

FUNCTION
sys.save() saves a lua table to a file stored on disk
sys.load() loads a lua table from a file on disk
sys.get_save_file() gets the save-file path
sys.get_application_path() gets the application path
sys.get_config() get config value
sys.get_config() get config value with default value
sys.open_url() open url in default application
sys.load_resource() loads resource from game data
sys.get_sys_info() get system information
sys.get_engine_info() get engine information
sys.get_application_info() get application information
sys.get_ifaddrs() enumerate network interfaces
sys.set_error_handler() set the error handler
sys.set_connectivity_host() set host to check for network connectivity against
sys.get_connectivity() get current network connectivity status
sys.exit() exits application
sys.reboot() reboot engine with arguments
sys.set_vsync_swap_interval() set vsync swap interval
sys.set_update_frequency() set update frequency
CONSTANT
sys.NETWORK_DISCONNECTED no network connection found
sys.NETWORK_CONNECTED_CELLULAR network connected through mobile cellular
sys.NETWORK_CONNECTED network connected through other, non cellular, connection
MESSAGE
exit exits application
toggle_profile shows/hides the on-screen profiler
toggle_physics_debug shows/hides the on-screen physics visual debugging
start_record starts video recording
stop_record stop current video recording
reboot reboot engine with arguments
set_vsync set vsync swap interval
set_update_frequency set update frequency

Functions

sys.save()

sys.save(filename,table)

The table can later be loaded by sys.load. Use sys.get_save_file to obtain a valid location for the file. Internally, this function uses a workspace buffer sized output file sized 512kb. This size reflects the output file size which must not exceed this limit. Additionally, the total number of rows that any one table may contain is limited to 65536 (i.e. a 16 bit range). When tables are used to represent arrays, the values of keys are permitted to fall within a 32 bit range, supporting sparse arrays, however the limit on the total number of rows remains in effect.

PARAMETERS

filename file to write to
table lua table to save

RETURNS

success a boolean indicating if the table could be saved or not

EXAMPLES

Save data:
local my_table = {}
table.insert(my_table, "my_value")
local my_file_path = sys.get_save_file("my_game", "my_file")
if not sys.save(my_file_path, my_table) then
  -- Alert user that the data could not be saved
end

sys.load()

sys.load(filename)

If the file exists, it must have been created by sys.save to be loaded.

PARAMETERS

filename file to read from

RETURNS

loaded lua table, which is empty if the file could not be found

EXAMPLES

Load data that was previously saved, e.g. an earlier game session:
local my_file_path = sys.get_save_file("my_game", "my_file")
local my_table = sys.load(my_file_path)
if not next(my_table) then
  -- empty table
end

sys.get_save_file()

sys.get_save_file(application_id,file_name)

The save-file path is operating system specific and is typically located under the user's home directory.

PARAMETERS

application_id user defined id of the application, which helps define the location of the save-file
file_name file-name to get path for

RETURNS

path path to save-file

EXAMPLES

Find a path where we can store data (the example path is on the macOS platform):
local my_file_path = sys.get_save_file("my_game", "my_file")
print(my_file_path) --> /Users/my_users/Library/Application Support/my_game/my_file

sys.get_application_path()

sys.get_application_path()

The path from which the application is run.

PARAMETERS

RETURNS

path path to application executable

EXAMPLES

Find a path where we can store data (the example path is on the macOS platform):
-- macOS: /Applications/my_game.app
local application_path = sys.get_application_path()
print(application_path) --> /Applications/my_game.app

-- Windows: C:\Program Files\my_game\my_game.exe
print(application_path) --> C:\Program Files\my_game

-- Linux: /home/foobar/my_game/my_game
print(application_path) --> /home/foobar/my_game

-- Android package name: com.foobar.my_game
print(application_path) --> /data/user/0/com.foobar.my_game

-- iOS: my_game.app
print(application_path) --> /var/containers/Bundle/Applications/123456AB-78CD-90DE-12345678ABCD/my_game.app

-- HTML5: http://www.foobar.com/my_game/
print(application_path) --> http://www.foobar.com/my_game

sys.get_config()

sys.get_config(key)

Get config value from the game.project configuration file. In addition to the project file, configuration values can also be passed to the runtime as command line arguments with the --config argument.

PARAMETERS

key key to get value for. The syntax is SECTION.KEY

RETURNS

value config value as a string. nil if the config key doesn't exists

EXAMPLES

Get display width
local width = tonumber(sys.get_config("display.width"))
Start the engine with a bootstrap config override and a custom config value
$ mygame --config=bootstrap.main_collection=/mytest.collectionc --config=mygame.testmode=1
Set and read a custom config value
local testmode = tonumber(sys.get_config("mygame.testmode"))

sys.get_config()

sys.get_config(key,default_value)

Get config value from the game.project configuration file with default value

PARAMETERS

key key to get value for. The syntax is SECTION.KEY
default_value default value to return if the value does not exist

RETURNS

value config value as a string. default_value if the config key does not exist

EXAMPLES

Get user config value
local speed = tonumber(sys.get_config("my_game.speed", "10.23"))

sys.open_url()

sys.open_url(url,[attributes])

Open URL in default application, typically a browser

PARAMETERS

url url to open
[attributes] table with attributes target - string : Optional. Specifies the target attribute or the name of the window. The following values are supported: - _self - URL replaces the current page. This is default. - _blank - URL is loaded into a new window, or tab. - _parent - URL is loaded into the parent frame. - _top - URL replaces any framesets that may be loaded. - name - The name of the window (Note: the name does not specify the title of the new window).

RETURNS

success a boolean indicating if the url could be opened or not

EXAMPLES

Open an URL:
local success = sys.open_url("http://www.defold.com", {target = "_blank"})
if not success then
  -- could not open the url...
end

sys.load_resource()

sys.load_resource(filename)

Loads a custom resource. Specify the full filename of the resource that you want to load. When loaded, the file data is returned as a string. If loading fails, the function returns nil plus the error message. In order for the engine to include custom resources in the build process, you need to specify them in the "custom_resources" key in your "game.project" settings file. You can specify single resource files or directories. If a directory is included in the resource list, all files and directories in that directory is recursively included: For example "main/data/,assets/level_data.json".

PARAMETERS

filename resource to load, full path

RETURNS

data loaded data, or nil if the resource could not be loaded
error the error message, or nil if no error occurred

EXAMPLES

-- Load level data into a string
local data, error = sys.load_resource("/assets/level_data.json")
-- Decode json string to a Lua table
if data then
  local data_table = json.decode(data)
  pprint(data_table)
else
  print(error)
end

sys.get_sys_info()

sys.get_sys_info()

Returns a table with system information.

PARAMETERS

RETURNS

sys_info table with system information in the following fields:
device_model
string Only available on iOS and Android.
manufacturer
string Only available on iOS and Android.
system_name
string The system OS name: "Darwin", "Linux", "Windows", "HTML5", "Android" or "iPhone OS"
system_version
string The system OS version.
api_version
string The API version on the system.
language
string Two character ISO-639 format, i.e. "en".
device_language
string Two character ISO-639 format (i.e. "sr") and, if applicable, followed by a dash (-) and an ISO 15924 script code (i.e. "sr-Cyrl" or "sr-Latn"). Reflects the device preferred language.
territory
string Two character ISO-3166 format, i.e. "US".
gmt_offset
number The current offset from GMT (Greenwich Mean Time), in minutes.
device_ident
string "identifierForVendor" on iOS. "android_id" on Android. On Android, you need to add READ_PHONE_STATE permission to be able to get this data. We don't use this permission in Defold.
user_agent
string The HTTP user agent, i.e. "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/602.4.8 (KHTML, like Gecko) Version/10.0.3 Safari/602.4.8"

EXAMPLES

How to get system information:
local info = sys.get_sys_info()
if info.system_name == "HTML5" then
  -- We are running in a browser.
end

sys.get_engine_info()

sys.get_engine_info()

Returns a table with engine information.

PARAMETERS

RETURNS

engine_info table with engine information in the following fields:
version
string The current Defold engine version, i.e. "1.2.96"
version_sha1
string The SHA1 for the current engine build, i.e. "0060183cce2e29dbd09c85ece83cbb72068ee050"
is_debug
boolean If the engine is a debug or release version

EXAMPLES

How to retrieve engine information:
-- Update version text label so our testers know what version we're running
local engine_info = sys.get_engine_info()
local version_str = "Defold " .. engine_info.version .. "\n" .. engine_info.version_sha1
gui.set_text(gui.get_node("version"), version_str)

sys.get_application_info()

sys.get_application_info(app_string)

Returns a table with application information for the requested app. On iOS, the app_string is an url scheme for the app that is queried. Your game needs to list the schemes that are queried in an LSApplicationQueriesSchemes array in a custom "Info.plist". On Android, the app_string is the package identifier for the app.

PARAMETERS

app_string platform specific string with application package or query, see above for details.

RETURNS

app_info table with application information in the following fields:
installed
boolean true if the application is installed, false otherwise.

EXAMPLES

Check if twitter is installed:
sysinfo = sys.get_sys_info()
twitter = {}

if sysinfo.system_name == "Android" then
  twitter = sys.get_application_info("com.twitter.android")
elseif sysinfo.system_name == "iPhone OS" then
  twitter = sys.get_application_info("twitter:")
end

if twitter.installed then
  -- twitter is installed!
end
Info.plist for the iOS app needs to list the schemes that are queried:
...
<key>LSApplicationQueriesSchemes</key>
 <array>
   <string>twitter</string>
 </array>
...

sys.get_ifaddrs()

sys.get_ifaddrs()

Returns an array of tables with information on network interfaces.

PARAMETERS

RETURNS

ifaddrs an array of tables. Each table entry contain the following fields:
name
string Interface name
address
string IP address. might be nil if not available.
mac
string Hardware MAC address. might be nil if not available.
up
boolean true if the interface is up (available to transmit and receive data), false otherwise.
running
boolean true if the interface is running, false otherwise.

EXAMPLES

How to get the IP address of interface "en0":
ifaddrs = sys.get_ifaddrs()
for _,interface in ipairs(ifaddrs) do
  if interface.name == "en0" then
    local ip = interface.address
  end
end

sys.set_error_handler()

sys.set_error_handler(error_handler)

Set the Lua error handler function. The error handler is a function which is called whenever a lua runtime error occurs.

PARAMETERS

error_handler the function to be called on error
source
string The runtime context of the error. Currently, this is always "lua".
message
string The source file, line number and error message.
traceback
string The stack traceback.

EXAMPLES

Install error handler that just prints the errors
local function my_error_handler(source, message, traceback)
  print(source)    --> lua
  print(message)   --> main/my.script:10: attempt to perform arithmetic on a string value
  print(traceback) --> stack traceback:
                   -->         main/test.script:10: in function 'boom'
                   -->         main/test.script:15: in function <main/my.script:13>
end

local function boom()
  return 10 + "string"
end

function init(self)
  sys.set_error_handler(my_error_handler)
  boom()
end

sys.set_connectivity_host()

sys.set_connectivity_host(host)

Sets the host that is used to check for network connectivity against.

PARAMETERS

host hostname to check against

EXAMPLES

sys.set_connectivity_host("www.google.com")

sys.get_connectivity()

sys.get_connectivity()

Returns the current network connectivity status on mobile platforms. On desktop, this function always return sys.NETWORK_CONNECTED.

PARAMETERS

RETURNS

status network connectivity status:
  • sys.NETWORK_DISCONNECTED (no network connection is found)
  • sys.NETWORK_CONNECTED_CELLULAR (connected through mobile cellular)
  • sys.NETWORK_CONNECTED (otherwise, Wifi)

EXAMPLES

Check if we are connected through a cellular connection
if (sys.NETWORK_CONNECTED_CELLULAR == sys.get_connectivity()) then
  print("Connected via cellular, avoid downloading big files!")
end

sys.exit()

sys.exit(code)

Terminates the game application and reports the specified code to the OS.

PARAMETERS

code exit code to report to the OS, 0 means clean exit

EXAMPLES

This examples demonstrates how to exit the application when some kind of quit messages is received (maybe from gui or similar):
function on_message(self, message_id, message, sender)
    if message_id == hash("quit") then
        sys.exit(0)
    end
end

sys.reboot()

sys.reboot(arg1,arg2,arg3,arg4,arg5,arg6)

Reboots the game engine with a specified set of arguments. Arguments will be translated into command line arguments. Calling reboot function is equivalent to starting the engine with the same arguments. On startup the engine reads configuration from "game.project" in the project root.

PARAMETERS

arg1 argument 1
arg2 argument 2
arg3 argument 3
arg4 argument 4
arg5 argument 5
arg6 argument 6

EXAMPLES

How to reboot engine with a specific bootstrap collection.
local arg1 = '--config=bootstrap.main_collection=/my.collectionc'
local arg2 = 'build/default/game.projectc'
sys.reboot(arg1, arg2)

sys.set_vsync_swap_interval()

sys.set_vsync_swap_interval(swap_interval)

Set the vsync swap interval. The interval with which to swap the front and back buffers in sync with vertical blanks (v-blank), the hardware event where the screen image is updated with data from the front buffer. A value of 1 swaps the buffers at every v-blank, a value of 2 swaps the buffers every other v-blank and so on. A value of 0 disables waiting for v-blank before swapping the buffers. Default value is 1. When setting the swap interval to 0 and having vsync disabled in "game.project", the engine will try to respect the set frame cap value from "game.project" in software instead. This setting may be overridden by driver settings.

PARAMETERS

swap_interval target swap interval.

EXAMPLES

Setting the swap intervall to swap every v-blank
sys.set_vsync_swap_interval(1)

sys.set_update_frequency()

sys.set_update_frequency(frequency)

Set game update-frequency (frame cap). This option is equivalent to display.update_frequency in the "game.project" settings but set in run-time. If Vsync checked in "game.project", the rate will be clamped to a swap interval that matches any detected main monitor refresh rate. If Vsync is unchecked the engine will try to respect the rate in software using timers. There is no guarantee that the frame cap will be achieved depending on platform specifics and hardware settings.

PARAMETERS

frequency target frequency. 60 for 60 fps

EXAMPLES

Setting the update frequency to 60 frames per second
sys.set_update_frequency(60)

Constants

sys.NETWORK_DISCONNECTED

no network connection found

no network connection found


sys.NETWORK_CONNECTED_CELLULAR

network connected through mobile cellular

network connected through mobile cellular


sys.NETWORK_CONNECTED

network connected through other, non cellular, connection

network connected through other, non cellular, connection


Messages

exit

exits application

Terminates the game application and reports the specified code to the OS. This message can only be sent to the designated @system socket.

code exit code to report to the OS, 0 means clean exit

EXAMPLES

This examples demonstrates how to exit the application when some kind of quit messages is received (maybe from gui or similar):
function on_message(self, message_id, message, sender)
    if message_id == hash("quit") then
        msg.post("@system:", "exit", {code = 0})
    end
end

toggle_profile

shows/hides the on-screen profiler

Toggles the on-screen profiler. The profiler is a real-time tool that shows the numbers of milliseconds spent in each scope per frame as well as counters. The profiler is very useful for tracking down performance and resource problems. In addition to the on-screen profiler, Defold includes a web-based profiler that allows you to sample a series of data points and then analyze them in detail. The web profiler is available at http://<device IP>:8002 where is the IP address of the device you are running your game on. This message can only be sent to the designated @system socket.

EXAMPLES

msg.post("@system:", "toggle_profile")

toggle_physics_debug

shows/hides the on-screen physics visual debugging

Toggles the on-screen physics visual debugging mode which is very useful for tracking down issues related to physics. This mode visualizes all collision object shapes and normals at detected contact points. Toggling this mode on is equal to setting physics.debug in the "game.project" settings, but set in run-time. This message can only be sent to the designated @system socket.

EXAMPLES

msg.post("@system:", "toggle_physics_debug")

start_record

starts video recording

Starts video recording of the game frame-buffer to file. Current video format is the open vp8 codec in the ivf container. It's possible to upload this format directly to YouTube. The VLC video player has native support but with the known issue that not the entire file is played back. It's probably an issue with VLC. The Miro Video Converter has support for vp8/ivf. Video recording is only supported on desktop platforms. Audio is currently not supported Window width and height must be a multiple of 8 to be able to record video. This message can only be sent to the designated @system socket.

file_name file name to write the video to
frame_period frame period to record, ie write every nth frame. Default value is 2
fps frames per second. Playback speed for the video. Default value is 30. The fps value doens't affect the recording. It's only meta-data in the written video file.

EXAMPLES

Record a video in 30 fps given that the native game fps is 60:
msg.post("@system:", "start_record", { file_name = "test_rec.ivf" } )
To write a video in 60 fps given that the native game fps is 60:
msg.post("@system:", "start_record", { file_name = "test_rec.ivf", frame_period = 1, fps = 60 } )

stop_record

stop current video recording

Stops the currently active video recording. Video recording is only supported on desktop platforms. This message can only be sent to the designated @system socket.

EXAMPLES

msg.post("@system:", "stop_record")

reboot

reboot engine with arguments

Reboots the game engine with a specified set of arguments. Arguments will be translated into command line arguments. Sending the reboot command is equivalent to starting the engine with the same arguments. On startup the engine reads configuration from "game.project" in the project root. This message can only be sent to the designated @system socket.

arg1 argument 1
arg2 argument 2
arg3 argument 3
arg4 argument 4
arg5 argument 5
arg6 argument 6

EXAMPLES

How to reboot engine with a specific bootstrap collection.
local arg1 = '--config=bootstrap.main_collection=/my.collectionc'
local arg2 = 'build/default/game.projectc'
msg.post("@system:", "reboot", {arg1 = arg1, arg2 = arg2})

set_vsync

set vsync swap interval

Set the vsync swap interval. The interval with which to swap the front and back buffers in sync with vertical blanks (v-blank), the hardware event where the screen image is updated with data from the front buffer. A value of 1 swaps the buffers at every v-blank, a value of 2 swaps the buffers every other v-blank and so on. A value of 0 disables waiting for v-blank before swapping the buffers. Default value is 1. When setting the swap interval to 0 and having vsync disabled in "game.project", the engine will try to respect the set frame cap value from "game.project" in software instead. This setting may be overridden by driver settings. This message can only be sent to the designated @system socket.

swap_interval target swap interval.

EXAMPLES

msg.post("@system:", "set_vsync", { swap_interval = 1 } )

set_update_frequency

set update frequency

Set game update-frequency (frame cap). This option is equivalent to display.update_frequency in the "game.project" settings but set in run-time. If Vsync checked in "game.project", the rate will be clamped to a swap interval that matches any detected main monitor refresh rate. If Vsync is unchecked the engine will try to respect the rate in software using timers. There is no guarantee that the frame cap will be achieved depending on platform specifics and hardware settings. This message can only be sent to the designated @system socket.

frequency target frequency. 60 for 60 fps

EXAMPLES

msg.post("@system:", "set_update_frequency", { frequency = 60 } )