Signal handler

gistfile1.hs

handler :: MVar Int -> IO ()
handler s_interrupted = trace "Interrupt received" $ do
    r <- readMVar s_interrupted
    trace ("value was " ++ show r) $ modifyMVar_ s_interrupted (return . (+1))
    
{- this prints on the first SIGTERM:

Interrupt received
value was 0

But then each new SIGTERM I only get

value was 1
value was 2
value was 3
value was 4
value was 5
value was 6
value was 7
value was 8
value was 9
value was 10
value was 11
value was 12
value was 13
value was 14
value was 15

-}