Haskell 管道化两个子流程时的快速行为

我有以下代码的活泼行为

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Control.Concurrent (threadDelay)
import qualified Control.Concurrent.Async      as Async
import qualified System.Process.Typed          as Proc
import qualified System.Process                as P
import qualified GHC.IO.Handle                 as H

main :: IO ()
main = do
  print "starting"

  (readEnd, writeEnd) <- P.createPipe

  let p1 = Proc.setStdout (Proc.useHandleClose writeEnd) "echo -n 'foo'"
  let p2 = Proc.setStdin (Proc.useHandleClose readEnd) "base64 -"

  Async.concurrently
    (threadDelay 1000 *> Proc.runProcess_ p2) -- with the delay, it works
    -- (Proc.runProcess_ p2) -- that line will make the program hang forever
    (Proc.runProcess_ p1)

  print "done"

---

System.Process.Typed

有一个

createPipe

方法，该方法返回一个streamspec，也许您应该使用它而不是

System.Process

的版本。有一个例子与您在of

类型化过程中所做的工作非常接近。它似乎只是关于父级和子级之间的通信，但并不直接处理子级之间的通信。
Proc.withProcess_ "echo -n foo" $ \r1 -> do
  let p2 = Proc.setStdin (Proc.getStdout r1) "base64"


  • Couldn't match expected type ‘Proc.StreamSpec
                                    'Proc.STInput stdin0’
                with actual type ‘()’
  • In the first argument of ‘Proc.setStdin’, namely
      ‘(Proc.getStdout r1)’
    In the expression: Proc.setStdin (Proc.getStdout r1) "base64"