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    1 -----------------------------------------------------------------------------
    2 -- |
    3 -- Module      :  Distribution.Client.Compat.Process
    4 -- Copyright   :  (c) 2013 Liu Hao, Brent Yorgey
    5 -- License     :  BSD-style (see the file LICENSE)
    6 --
    7 -- Maintainer  :  cabal-devel@haskell.org
    8 -- Stability   :  provisional
    9 -- Portability :  portable
   10 --
   11 -- Cross-platform utilities for invoking processes.
   12 --
   13 -----------------------------------------------------------------------------
   14 
   15 module Distribution.Client.Compat.Process (
   16   readProcessWithExitCode
   17 ) where
   18 
   19 import Prelude (FilePath, IO, String, return, (||))
   20 
   21 import           Control.Exception (catch, throw)
   22 import           System.Exit       (ExitCode (ExitFailure))
   23 import           System.IO.Error   (isDoesNotExistError, isPermissionError)
   24 import qualified System.Process    as P
   25 
   26 -- | @readProcessWithExitCode@ creates an external process, reads its
   27 --   standard output and standard error strictly, waits until the
   28 --   process terminates, and then returns the @ExitCode@ of the
   29 --   process, the standard output, and the standard error.
   30 --
   31 --   See the documentation of the version from @System.Process@ for
   32 --   more information.
   33 --
   34 --   The version from @System.Process@ behaves inconsistently across
   35 --   platforms when an executable with the given name is not found: in
   36 --   some cases it returns an @ExitFailure@, in others it throws an
   37 --   exception.  This variant catches \"does not exist\" and
   38 --   \"permission denied\" exceptions and turns them into
   39 --   @ExitFailure@s.
   40 --
   41 -- TODO: this doesn't use 'Distrubution.Compat.Process'.
   42 --
   43 readProcessWithExitCode :: FilePath -> [String] -> String -> IO (ExitCode, String, String)
   44 readProcessWithExitCode cmd args input =
   45   P.readProcessWithExitCode cmd args input
   46     `catch` \e -> if isDoesNotExistError e || isPermissionError e
   47                     then return (ExitFailure 127, "", "")
   48                     else throw e