File system

Revision as of 04:04, 10 May 2020 by MoKaLux (talk | contribs) (some updates)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

The Ultimate Guide to Gideros Studio

File system

In Gideros runtime, there are 3 kinds of directories:

  • resource directory
  • document directory
  • temporary directory

Resource directory

Your code, images, audios and all other files reside in the resource directory. Consider the test project below, and examine the 3 directories and corresponding files.

Resource directory.png

The files seen above are stored on a real device and Gideros Player like the following:

{resource directory}/gfx/sprite1.png
{resource directory}/gfx/sprite2.png
{resource directory}/gfx/background.png
{resource directory}/audio/game-music.mp3
{resource directory}/audio/click.wav
{resource directory}/data/list.txt
{resource directory}/main.lua
{resource directory}/game.lua

The resource directory is the default directory. Therefore, to access the files you specify the file path as it is:

local sprite1 ="gfx/sprite1.png")
local sprite2 ="gfx/sprite2.png")
local background ="gfx/background.png")
local music ="audio/game-music.mp3")
local click ="audio/click.wav")

You can also use the io library provided by Lua:"data/list.txt")

Note: the resource directory is read-only and you should not try to write any files there.

Note: you can access the files in the resource directory by adding "|R|" at the beginning of the file name, but you don't need to:

local sprite1 ="|R|gfx/sprite1.png")

Document directory

You can store a file created by your application in the document directory. The files created in this directory are permanent among application sessions. For example, you can create and then read files in the document directory to save player progress, or keep latest GPS coordinates, ...

In order to specify a file in the document directory, append |D| to the beginning of the filename:


Here is an example of how you can copy a file from the resource directory to the document directory:

--function to copy file
local function copy(src, dst)
    local srcf =, "rb")
    local dstf =, "wb")

    local size = 2^13    -- good buffer size (8K)
    while true do
        local block = srcf:read(size)
        if not block then break end


--function to check if file exists
local function exists(file)
    local f =, "rb")
    if f == nil then
        return false
    return true

if not exists("|D|database.db") then
    copy("database.db", "|D|database.db")

Temporary directory

Gideros Studio provides a temporary directory to store files that may not stay permanent between different sessions. Therefore, files created in this directory are not guaranteed to exist when the application runs next time, and may be deleted after the application session finishes.

In order to specify a file in the temporary directory, append |T| to the beginning of the file name. Example:


This storage may be used to display some temporary data, like in the following example, images downloaded from the internet:

--download completed
local function onComplete(event)
	--store image in temporary folder
	local out ="|T|image.png", "wb")

	--display it to user
	local b ="|T|image.png"))
	b:setAnchorPoint(0.5, 0.5)
	b:setPosition(160, 240)

--load image
local loader ="")

--add event listener
loader:addEventListener(Event.COMPLETE, onComplete)

To sum up

Here is a list of possible file operations:"file.txt") -- open file.txt in the resource directory to read"|R|file.txt") -- open file.txt in the resource directory to read (same as above)"|D|file.txt") -- open file.txt in the document directory to read"|T|file.txt") -- open file.txt in the temporary directory to read

File execution order

By default Gideros executes all your project Lua files in the following order:

  • init.lua will always be executed first
  • then all the files in alphabetical order (upper case first, then lowercase), while resolving code dependencies
  • main.lua will always be executed last

Note: the rule about main.lua and init.lua only applies to top level files. If they are in sub directories, they lose their specificity.


strict.lua checks uses of undeclared global variables.

If strict.lua is executed, all global variables must be ‘declared’ through a regular assignment (even assigning nil will do) in a main chunk before being used anywhere or assigned to inside a function.

Although optional, it is a good habit to use it when developing Lua code.

For a detailed explanation of strict.lua, please refer to

To execute strict.lua before all other Lua files, simply add strict.lua and init.lua to asset library and make strict.lua dependent to init.lua.

You can download strict.lua from File:Strict.lua that originally comes with the Lua distribution.

PREV.: Event system
NEXT: Profiling