haskell - 如何在 Haskell 中编写 Ctrl-C 处理程序？

Question

我尝试了以下方法:

import System.Exit
import System.Posix.Signals
import Control.Concurrent (threadDelay)

main :: IO ()
main = do
  installHandler keyboardSignal (Catch (do exitSuccess)) Nothing
  threadDelay (1000000000)

但它只输出:

^CTest.hs: ExitSuccess

在 Ctrl-C ，而不是退出。我应该如何正确地做到这一点？

Answer 1

来自 installHandler 的文档:

a handler is installed which will invoke action in a new thread when (or shortly after) the signal is received.

和 exitWith:

Note: in GHC, exitWith should be called from the main program thread in order to exit the process. When called from another thread, exitWith will throw an ExitException as normal, but the exception will not cause the process itself to exit.

所以一个 exitSuccess处理程序不会结束该过程，这是预期的(尽管是意外的；)行为。

如果您想立即采取行动，

import System.Exit
import System.Posix.Signals
import Control.Concurrent

main :: IO ()
main = do
  tid <- myThreadId
  installHandler keyboardSignal (Catch (killThread tid)) Nothing
  threadDelay (1000000000)

收到信号后立即杀死线程。

不那么激烈，如果你想成功退出，那就是

import System.Exit
import System.Posix.Signals
import Control.Concurrent
import qualified Control.Exception as E

main :: IO ()
main = do
  tid <- myThreadId
  installHandler keyboardSignal (Catch (E.throwTo tid ExitSuccess)) Nothing
  threadDelay (10000000)

我认为它也可以可靠地工作，但我不完全确定。