{- portable environment variables - - Copyright 2013 Joey Hess - - License: BSD-2-clause -} {-# LANGUAGE CPP #-} module Utility.Env where #ifdef mingw32_HOST_OS import Utility.Exception import Control.Applicative import Data.Maybe import qualified System.Environment as E #else import qualified System.Posix.Env as PE #endif getEnv :: String -> IO (Maybe String) #ifndef mingw32_HOST_OS getEnv = PE.getEnv #else getEnv = catchMaybeIO . E.getEnv #endif getEnvDefault :: String -> String -> IO String #ifndef mingw32_HOST_OS getEnvDefault = PE.getEnvDefault #else getEnvDefault var fallback = fromMaybe fallback <$> getEnv var #endif getEnvironment :: IO [(String, String)] #ifndef mingw32_HOST_OS getEnvironment = PE.getEnvironment #else getEnvironment = E.getEnvironment #endif {- Returns True if it could successfully set the environment variable. - - There is, apparently, no way to do this in Windows. Instead, - environment varuables must be provided when running a new process. -} setEnv :: String -> String -> Bool -> IO Bool #ifndef mingw32_HOST_OS setEnv var val overwrite = do PE.setEnv var val overwrite return True #else setEnv _ _ _ = return False #endif {- Returns True if it could successfully unset the environment variable. -} unsetEnv :: String -> IO Bool #ifndef mingw32_HOST_OS unsetEnv var = do PE.unsetEnv var return True #else unsetEnv _ = return False #endif {- Adds the environment variable to the input environment. If already - present in the list, removes the old value. - - This does not really belong here, but Data.AssocList is for some reason - buried inside hxt. -} addEntry :: Eq k => k -> v -> [(k, v)] -> [(k, v)] addEntry k v l = ( (k,v) : ) $! delEntry k l addEntries :: Eq k => [(k, v)] -> [(k, v)] -> [(k, v)] addEntries = foldr (.) id . map (uncurry addEntry) . reverse delEntry :: Eq k => k -> [(k, v)] -> [(k, v)] delEntry _ [] = [] delEntry k (x@(k1,_) : rest) | k == k1 = rest | otherwise = ( x : ) $! delEntry k rest