在Haskell命令行应用程序中提示输入密码 [英] Prompting for a password in Haskell command line application

问题描述

以下Haskell程序提示用户在终端中输入密码，如果输入了正确的密码，则继续操作:

The following Haskell program prompts the user for a password in the terminal and continues if he has entered the correct one:

main = do
    putStrLn "Password:"
    password <- getLine

    case hash password `member` database of
        False -> putStrLn "Unauthorized use!"
        True  -> do
                 ...

不幸的是，密码会在用户键入时显示在屏幕上，我想避免这种情况.

Unfortunately, the password will appear on the screen as the user types it, which I want to avoid.

如何在不显示在屏幕上的情况下读取用户键入的字符序列?为此，getLine等于什么?

我使用的是MacOS X，但我希望它也可以在Windows和Linux上使用.

I'm on MacOS X, but I would like this to work on Windows and Linux, too.

推荐答案

执行以下操作:

module Main
where

import System.IO
import Control.Exception

main :: IO ()
main = getPassword >>= putStrLn . ("Entered: " ++)

getPassword :: IO String
getPassword = do
  putStr "Password: "
  hFlush stdout
  pass <- withEcho False getLine
  putChar '\n'
  return pass

withEcho :: Bool -> IO a -> IO a
withEcho echo action = do
  old <- hGetEcho stdin
  bracket_ (hSetEcho stdin echo) (hSetEcho stdin old) action

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