How to lock a script during execution?

[twodbvba]

Hi,
 
In a project, we use a pushbutton on KNX which triggers a LM4 script that gives instruction to the intercom to give a doorbell sound. But… when they push more than 1 time (like a couples of times directly after eachother), the intercom gets a couple of times the instruction and gets confused.
 
What is the best way to avoid that a running script is executed a second time?
 
Thanks!

[admin]

You can use storage to save last script execution time.
This example allows a script to be executed once in 5 seconds, you can tune the timer value as required:

Code:

now = os.time()
prevsend = storage.get('prevsendtime', 0)
delta = now - prevsend

if delta < 0 or delta > 5 then
  storage.set('prevsendtime', now)
  alert('executing script')
end

Another advanced approach is to lock any event script from executing in parallel by using semaphores:
http://openrb.com/docs/semaphore.htm

[twodbvba]

Can disabling and enabling the script work? So, at the first line of the script "disable" itself and at the last line "enable" itself?

[admin]

That will introduce race condition and it will fail from time to time. The only guaranteed way is to use semaphores.