When we create a new thread, we can keep track of its corresponding thread ID to kill it later manually.
In this recipe, we will be creating a command-line interface for forking new processes to download a huge file. A download will be initiated with the d command followed by a number. So, running d 1 will launch a thread to download item #1.
We will learn how to kill threads while they are still running. Our command to kill threads will look like k 1 in order to kill the downloaded item #1.
In a new file, which we call Main.hs, insert the following code:
Import the required packages as follows:
import Control.Concurrent import qualified Data.Map as M
Let
maincall the helperdownloadfunction:main = download (M.empty :: M.Map Int [ThreadId])
Define a function to take the user queries and appropriately respond as follows:
download m = do input <- (getLine >>= return . words) respond m input >>= download
Respond to a download request:
respond m...