Creating a timer using Lua - timer

Question

I would like to create a timer using Lua, in a way that I could specify a callback function to be triggered after X seconds have passed.
What would be the best way to achieve this? ( I need to download some data from a webserver that will be parsed once or twice an hour )
Cheers.

Answer 1

If milisecond accuracy is not needed, you could just go for a coroutine solution, which you resume periodically, like at the end of your main loop, Like this:
require 'socket' -- for having a sleep function ( could also use os.execute(sleep 10))
timer = function (time)
local init = os.time()
local diff=os.difftime(os.time(),init)
while diff<time do
coroutine.yield(diff)
diff=os.difftime(os.time(),init)
end
print( 'Timer timed out at '..time..' seconds!')
end
co=coroutine.create(timer)
coroutine.resume(co,30) -- timer starts here!
while coroutine.status(co)~="dead" do
print("time passed",select(2,coroutine.resume(co)))
print('',coroutine.status(co))
socket.sleep(5)
end
This uses the sleep function in LuaSocket, you could use any other of the alternatives suggested on the Lua-users Wiki

Answer 2

Try lalarm, here:
http://www.tecgraf.puc-rio.br/~lhf/ftp/lua/
Example (based on src/test.lua):
-- alarm([secs,[func]])
alarm(1, function() print(2) end); print(1)
Output:
1
2

Answer 3

If it's acceptable for you, you can try LuaNode. The following code sets a timer:
setInterval(function()
console.log("I run once a minute")
end, 60000)
process:loop()

Answer 4

use Script.SetTimer(interval, callbackFunction)

Answer 5

After reading this thread and others I decided to go with Luv lib. Here is my solution:
uv = require('luv') --luarocks install luv
function set_timeout(timeout, callback)
local timer = uv.new_timer()
local function ontimeout()
uv.timer_stop(timer)
uv.close(timer)
callback()
end
uv.timer_start(timer, timeout, 0, ontimeout)
return timer
end
set_timeout(1000, function() print('ok') end) -- time in ms
uv.run() --it will hold at this point until every timer have finished

Answer 6

On my Debian I've install lua-lgi packet to get access to the GObject based libraries.
The following code show you an usage demonstrating that you can use few asynchronuous callbacks:
local lgi = require 'lgi'
local GLib = lgi.GLib
-- Get the main loop object that handles all the events
local main_loop = GLib.MainLoop()
cnt = 0
function tictac()
cnt = cnt + 1
print("tic")
-- This callback will be called until the condition is true
return cnt < 10
end
-- Call tictac function every 2 senconds
GLib.timeout_add_seconds(GLib.PRIORITY_DEFAULT, 2, tictac)
-- You can also use an anonymous function like that
GLib.timeout_add_seconds(GLib.PRIORITY_DEFAULT, 1,
function()
print( "There have been ", cnt, "tic")
-- This callback will never stop
return true
end)
-- Once everything is setup, you can start the main loop
main_loop:run()
-- Next instructions will be still interpreted
print("Main loop is running")
You can find more documentation about LGI here