ref: d546dc31e3e45bc5369989e797d6c3c3fc885f9c
dir: /lib/System/Environment.hs/
-- Copyright 2023 Lennart Augustsson
-- See LICENSE file for full license.
module System.Environment(
getArgs,
getProgName,
withArgs,
lookupEnv,
) where
import Prelude
import Primitives(primPerformIO, primGetArgs)
import Data.IORef
import Foreign.C.String
import Foreign.Ptr
progArgs :: IORef [String]
progArgs = primPerformIO $ do
args <- primGetArgs
newIORef args
getArgs :: IO [String]
getArgs = readIORef progArgs
withArgs :: forall a . [String] -> IO a -> IO a
withArgs as ioa = do
old <- readIORef progArgs
writeIORef progArgs as
a <- ioa
writeIORef progArgs old
return a
foreign import ccall "getenv" c_getenv :: CString -> IO CString
lookupEnv :: String -> IO (Maybe String)
lookupEnv var = do
cptr <- withCAString var c_getenv
if cptr == nullPtr then
return Nothing
else
Just <$> peekCAString cptr
-- XXX implement this
getProgName :: IO String
getProgName = return "???"