Forking I/O actions for concurrency

A quick and easy way to launch an I/O type function in the background is by calling the forkIO function provided by the Control.Concurrent package. In this recipe, we will demonstrate simple input/output concurrently in Haskell. We will get the number of seconds to wait from the user input, and in the background, it will sleep and print a message once the thread wakes up.

How to do it…

1. Import the built-in concurrency package as follows:

   import Control.Concurrent (forkIO, threadDelay)

2. Ask the user the number of seconds the program has to sleep for. Then, sleep for that many seconds by calling our sleep function defined in the following code snippet. Finally, recursively call main again to demonstrate that the user can continue to input while a thread is running in the background:

   main = do
     putStr "Enter number of seconds to sleep: "
     time <- fmap (read :: String -> Int) getLine
     forkIO $ sleep time
     main

3. Define a function that takes...