System/Process/Internals.hs

    {-# LANGUAGE CPP #-}
    {-# OPTIONS_HADDOCK not-home #-}
    {-# LANGUAGE Trustworthy #-}
    {-# LANGUAGE InterruptibleFFI #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  System.Process.Internals
    -- Copyright   :  (c) The University of Glasgow 2004
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  experimental
    -- Portability :  portable
    --
    -- __Note:__ This module exports internal implementation details that may
    -- change anytime.  If you want a more stable API, use "System.Process"
    -- instead.
    --
    -----------------------------------------------------------------------------

    module System.Process.Internals (
        ProcessHandle(..), ProcessHandle__(..),
        PHANDLE, closePHANDLE, mkProcessHandle,
        modifyProcessHandle, withProcessHandle,
        CreateProcess(..),
        CmdSpec(..), StdStream(..),
        createProcess_,
        runGenProcess_, --deprecated
        fdToHandle,
        startDelegateControlC,
        endDelegateControlC,
        stopDelegateControlC,
    #ifndef WINDOWS
        pPrPr_disableITimers, c_execvpe,
        ignoreSignal, defaultSignal,
    #endif
        withFilePathException, withCEnvironment,
        translate,
        createPipe,
        createPipeFd,
        interruptProcessGroupOf,
        ) where

    import Foreign.C
    import System.IO

    import GHC.IO.Handle.FD (fdToHandle)
    import System.Posix.Internals (FD)

    import System.Process.Common

    #ifdef WINDOWS
    import System.Process.Windows
    #else
    import System.Process.Posix
    #endif

    -- ----------------------------------------------------------------------------

    -- | This function is almost identical to
    -- 'System.Process.createProcess'. The only differences are:
    --
    -- * 'Handle's provided via 'UseHandle' are not closed automatically.
    --
    -- * This function takes an extra @String@ argument to be used in creating
    --   error messages.
    --
    -- This function has been available from the "System.Process.Internals" module
    -- for some time, and is part of the "System.Process" module since version
    -- 1.2.1.0.
    --
    -- @since 1.2.1.0
    createProcess_
      :: String                     -- ^ function name (for error messages)
      -> CreateProcess
      -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
    createProcess_ = createProcess_Internal
    {-# INLINE createProcess_ #-}

    -- ------------------------------------------------------------------------
    -- Escaping commands for shells

    {-
    On Windows we also use this for running commands.  We use CreateProcess,
    passing a single command-line string (lpCommandLine) as its argument.
    (CreateProcess is well documented on http://msdn.microsoft.com.)

          - It parses the beginning of the string to find the command. If the
            file name has embedded spaces, it must be quoted, using double
            quotes thus
                    "foo\this that\cmd" arg1 arg2

          - The invoked command can in turn access the entire lpCommandLine string,
            and the C runtime does indeed do so, parsing it to generate the
            traditional argument vector argv[0], argv[1], etc.  It does this
            using a complex and arcane set of rules which are described here:

               https://msdn.microsoft.com/en-us/library/a1y7w461.aspx

            (if this URL stops working, you might be able to find it by
            searching for "Parsing C Command-Line Arguments" on MSDN.  Also,
            the code in the Microsoft C runtime that does this translation
            is shipped with VC++).

    Our goal in runProcess is to take a command filename and list of
    arguments, and construct a string which inverts the translatsions
    described above, such that the program at the other end sees exactly
    the same arguments in its argv[] that we passed to rawSystem.

    This inverse translation is implemented by 'translate' below.

    Here are some pages that give informations on Windows-related
    limitations and deviations from Unix conventions:

        http://support.microsoft.com/default.aspx?scid=kb;en-us;830473
        Command lines and environment variables effectively limited to 8191
        characters on Win XP, 2047 on NT/2000 (probably even less on Win 9x):

        http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/percent.asp
        Command-line substitution under Windows XP. IIRC these facilities (or at
        least a large subset of them) are available on Win NT and 2000. Some
        might be available on Win 9x.

        http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/Cmd.asp
        How CMD.EXE processes command lines.

    Note: CreateProcess does have a separate argument (lpApplicationName)
    with which you can specify the command, but we have to slap the
    command into lpCommandLine anyway, so that argv[0] is what a C program
    expects (namely the application name).  So it seems simpler to just
    use lpCommandLine alone, which CreateProcess supports.
    -}

    translate :: String -> String
    translate = translateInternal
    {-# INLINE translate #-}

    -- ----------------------------------------------------------------------------
    -- Deprecated / compat

    {-# DEPRECATED runGenProcess_
          "Please do not use this anymore, use the ordinary 'System.Process.createProcess'. If you need the SIGINT handling, use delegate_ctlc = True (runGenProcess_ is now just an imperfectly emulated stub that probably duplicates or overrides your own signal handling)." #-}
    runGenProcess_
     :: String                     -- ^ function name (for error messages)
     -> CreateProcess
     -> Maybe CLong                -- ^ handler for SIGINT
     -> Maybe CLong                -- ^ handler for SIGQUIT
     -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
    -- On Windows, setting delegate_ctlc has no impact
    runGenProcess_ fun c (Just sig) (Just sig') | isDefaultSignal sig && sig == sig'
                             = createProcess_ fun c { delegate_ctlc = True }
    runGenProcess_ fun c _ _ = createProcess_ fun c

    -- ---------------------------------------------------------------------------
    -- createPipe

    -- | Create a pipe for interprocess communication and return a
    -- @(readEnd, writeEnd)@ `Handle` pair.
    --
    -- @since 1.2.1.0
    createPipe :: IO (Handle, Handle)
    createPipe = createPipeInternal
    {-# INLINE createPipe #-}

    -- ---------------------------------------------------------------------------
    -- createPipeFd

    -- | Create a pipe for interprocess communication and return a
    -- @(readEnd, writeEnd)@ `FD` pair.
    --
    -- @since 1.4.2.0
    createPipeFd :: IO (FD, FD)
    createPipeFd = createPipeInternalFd
    {-# INLINE createPipeFd #-}

    -- ----------------------------------------------------------------------------
    -- interruptProcessGroupOf

    -- | Sends an interrupt signal to the process group of the given process.
    --
    -- On Unix systems, it sends the group the SIGINT signal.
    --
    -- On Windows systems, it generates a CTRL_BREAK_EVENT and will only work for
    -- processes created using 'createProcess' and setting the 'create_group' flag

    interruptProcessGroupOf
        :: ProcessHandle    -- ^ A process in the process group
        -> IO ()
    interruptProcessGroupOf = interruptProcessGroupOfInternal