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Diffstat (limited to 'compat/Compat/RawSystem.hs')
| -rw-r--r-- | compat/Compat/RawSystem.hs | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/compat/Compat/RawSystem.hs b/compat/Compat/RawSystem.hs new file mode 100644 index 0000000000..f0f8aa3ac7 --- /dev/null +++ b/compat/Compat/RawSystem.hs @@ -0,0 +1,156 @@ +{-# OPTIONS -cpp #-} +----------------------------------------------------------------------------- +-- | +-- Module : Compat.RawSystem +-- Copyright : (c) The University of Glasgow 2001-2004 +-- License : BSD-style (see the file libraries/base/LICENSE) +-- +-- Maintainer : libraries@haskell.org +-- Stability : provisional +-- Portability : portable +-- +-- This is an implementation of rawSystem for use on older versions of GHC +-- which had missing or buggy implementations of this function. +-- +----------------------------------------------------------------------------- + +module Compat.RawSystem (rawSystem) where + +#include "../../includes/ghcconfig.h" + +#if __GLASGOW_HASKELL__ >= 603 + +import System.Cmd (rawSystem) + +#else /* to end of file */ + +import System.Exit +import Foreign +import Foreign.C + +{- | +The computation @'rawSystem' cmd args@ runs the operating system command +whose file name is @cmd@, passing it the arguments @args@. It +bypasses the shell, so that @cmd@ should see precisely the argument +strings @args@, with no funny escaping or shell meta-syntax expansion. +(Unix users will recognise this behaviour +as @execvp@, and indeed that's how it's implemented.) +It will therefore behave more portably between operating systems than 'system'. + +The return codes are the same as for 'system'. +-} + +rawSystem :: FilePath -> [String] -> IO ExitCode + +{- ------------------------------------------------------------------------- + IMPORTANT IMPLEMENTATION NOTES + (see also libraries/base/cbits/rawSystem.c) + +On Unix, rawSystem is easy to implement: use execvp. + +On Windows it's more tricky. 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: + + http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/progs_12.asp + + (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 rawSystem 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. + +----------------------------------------------------------------------------- -} + +#ifndef mingw32_HOST_OS + +rawSystem cmd args = + withCString cmd $ \pcmd -> + withMany withCString (cmd:args) $ \cstrs -> + withArray0 nullPtr cstrs $ \arr -> do + status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmd arr) + case status of + 0 -> return ExitSuccess + n -> return (ExitFailure n) + +foreign import ccall unsafe "rawSystem" + c_rawSystem :: CString -> Ptr CString -> IO Int + +#else + +-- On Windows, the command line is passed to the operating system as +-- a single string. Command-line parsing is done by the executable +-- itself. +rawSystem cmd args = do + -- NOTE: 'cmd' is assumed to contain the application to run _only_, + -- as it'll be quoted surrounded in quotes here. + let cmdline = translate cmd ++ concat (map ((' ':) . translate) args) + withCString cmdline $ \pcmdline -> do + status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmdline) + case status of + 0 -> return ExitSuccess + n -> return (ExitFailure n) + +translate :: String -> String +translate str@('"':_) = str -- already escaped. + -- ToDo: this case is wrong. It is only here because we + -- abuse the system in GHC's SysTools by putting arguments into + -- the command name; at some point we should fix it up and remove + -- the case above. +translate str = '"' : snd (foldr escape (True,"\"") str) + where escape '"' (b, str) = (True, '\\' : '"' : str) + escape '\\' (True, str) = (True, '\\' : '\\' : str) + escape '\\' (False, str) = (False, '\\' : str) + escape c (b, str) = (False, c : str) + -- See long comment above for what this function is trying to do. + -- + -- The Bool passed back along the string is True iff the + -- rest of the string is a sequence of backslashes followed by + -- a double quote. + +foreign import ccall unsafe "rawSystem" + c_rawSystem :: CString -> IO Int + +#endif + +#endif + |