{-# LINE 1 "libraries/base/System/Environment/ExecutablePath.hsc" #-}
{-# LANGUAGE Safe #-}
{-# LANGUAGE CPP #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  System.Environment.ExecutablePath
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- Function to retrieve the absolute filepath of the current executable.
--
-- @since 4.6.0.0
-----------------------------------------------------------------------------

module System.Environment.ExecutablePath
  ( getExecutablePath
  , executablePath
  ) where

-- The imports are purposely kept completely disjoint to prevent edits
-- to one OS implementation from breaking another.


{-# LINE 37 "libraries/base/System/Environment/ExecutablePath.hsc" #-}
import Data.List (isSuffixOf)
import Foreign.C
import Foreign.Marshal.Array
import System.Posix.Internals

{-# LINE 69 "libraries/base/System/Environment/ExecutablePath.hsc" #-}

-- The exported function is defined outside any if-guard to make sure
-- every OS implements it with the same type.

-- | Returns the absolute pathname of the current executable,
-- or @argv[0]@ if the operating system does not provide a reliable
-- way query the current executable.
--
-- Note that for scripts and interactive sessions, this is the path to
-- the interpreter (e.g. ghci.)
--
-- Since base 4.11.0.0, 'getExecutablePath' resolves symlinks on Windows.
-- If an executable is launched through a symlink, 'getExecutablePath'
-- returns the absolute path of the original executable.
--
-- If the executable has been deleted, behaviour is ill-defined and
-- varies by operating system.  See 'executablePath' for a more
-- reliable way to query the current executable.
--
-- @since 4.6.0.0
getExecutablePath :: IO FilePath

-- | Get an action to query the absolute pathname of the current executable.
--
-- If the operating system provides a reliable way to determine the current
-- executable, return the query action, otherwise return @Nothing@.  The action
-- is defined on FreeBSD, Linux, MacOS and Windows.
--
-- Even where the query action is defined, there may be situations where no
-- result is available, e.g. if the executable file was deleted while the
-- program is running.  Therefore the result of the query action is a @Maybe
-- FilePath@.
--
-- Note that for scripts and interactive sessions, the result is the path to
-- the interpreter (e.g. ghci.)
--
-- @since 4.17.0.0
executablePath :: Maybe (IO (Maybe FilePath))


--------------------------------------------------------------------------------
-- Mac OS X


{-# LINE 164 "libraries/base/System/Environment/ExecutablePath.hsc" #-}

foreign import ccall unsafe "readlink"
    c_readlink :: CString -> CString -> CSize -> IO CInt

-- | Reads the @FilePath@ pointed to by the symbolic link and returns
-- it.
--
-- See readlink(2)
readSymbolicLink :: FilePath -> IO FilePath
readSymbolicLink file =
    allocaArray0 4096 $ \buf ->
        withFilePath file $ \s -> do
            len <- throwErrnoPathIfMinus1 "readSymbolicLink" file $
                   c_readlink s buf 4096
            peekFilePathLen (buf,fromIntegral len)

getExecutablePath = readSymbolicLink $ "/proc/self/exe"

executablePath = Just (check <$> getExecutablePath) where
  -- procfs(5): If the pathname has been unlinked, the symbolic link will
  -- contain the string '(deleted)' appended to the original pathname.
  --
  -- See also https://gitlab.haskell.org/ghc/ghc/-/issues/10957
  check s | "(deleted)" `isSuffixOf` s = Nothing
          | otherwise = Just s

--------------------------------------------------------------------------------
-- FreeBSD


{-# LINE 363 "libraries/base/System/Environment/ExecutablePath.hsc" #-}