2 -----------------------------------------------------------------------------
4 -- Module : Compat.RawSystem
5 -- Copyright : (c) The University of Glasgow 2001-2004
6 -- License : BSD-style (see the file libraries/base/LICENSE)
8 -- Maintainer : libraries@haskell.org
9 -- Stability : provisional
10 -- Portability : portable
12 -- This is an implementation of rawSystem for use on older versions of GHC
13 -- which had missing or buggy implementations of this function.
15 -----------------------------------------------------------------------------
17 module Compat.RawSystem (rawSystem) where
19 #if __GLASGOW_HASKELL__ < 603
23 #if __GLASGOW_HASKELL__ >= 603
25 import System.Cmd (rawSystem)
27 #else /* to end of file */
34 The computation @'rawSystem' cmd args@ runs the operating system command
35 whose file name is @cmd@, passing it the arguments @args@. It
36 bypasses the shell, so that @cmd@ should see precisely the argument
37 strings @args@, with no funny escaping or shell meta-syntax expansion.
38 (Unix users will recognise this behaviour
39 as @execvp@, and indeed that's how it's implemented.)
40 It will therefore behave more portably between operating systems than 'system'.
42 The return codes are the same as for 'system'.
45 rawSystem :: FilePath -> [String] -> IO ExitCode
47 {- -------------------------------------------------------------------------
48 IMPORTANT IMPLEMENTATION NOTES
49 (see also libraries/base/cbits/rawSystem.c)
51 On Unix, rawSystem is easy to implement: use execvp.
53 On Windows it's more tricky. We use CreateProcess, passing a single
54 command-line string (lpCommandLine) as its argument. (CreateProcess
55 is well documented on http://msdn.microsoft/com.)
57 - It parses the beginning of the string to find the command. If the
58 file name has embedded spaces, it must be quoted, using double
60 "foo\this that\cmd" arg1 arg2
62 - The invoked command can in turn access the entire lpCommandLine string,
63 and the C runtime does indeed do so, parsing it to generate the
64 traditional argument vector argv[0], argv[1], etc. It does this
65 using a complex and arcane set of rules which are described here:
67 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/progs_12.asp
69 (if this URL stops working, you might be able to find it by
70 searching for "Parsing C Command-Line Arguments" on MSDN. Also,
71 the code in the Microsoft C runtime that does this translation
72 is shipped with VC++).
75 Our goal in rawSystem is to take a command filename and list of
76 arguments, and construct a string which inverts the translatsions
77 described above, such that the program at the other end sees exactly
78 the same arguments in its argv[] that we passed to rawSystem.
80 This inverse translation is implemented by 'translate' below.
82 Here are some pages that give informations on Windows-related
83 limitations and deviations from Unix conventions:
85 http://support.microsoft.com/default.aspx?scid=kb;en-us;830473
86 Command lines and environment variables effectively limited to 8191
87 characters on Win XP, 2047 on NT/2000 (probably even less on Win 9x):
89 http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/percent.asp
90 Command-line substitution under Windows XP. IIRC these facilities (or at
91 least a large subset of them) are available on Win NT and 2000. Some
92 might be available on Win 9x.
94 http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/Cmd.asp
95 How CMD.EXE processes command lines.
98 Note: CreateProcess does have a separate argument (lpApplicationName)
99 with which you can specify the command, but we have to slap the
100 command into lpCommandLine anyway, so that argv[0] is what a C program
101 expects (namely the application name). So it seems simpler to just
102 use lpCommandLine alone, which CreateProcess supports.
104 ----------------------------------------------------------------------------- -}
106 #ifndef mingw32_TARGET_OS
109 withCString cmd $ \pcmd ->
110 withMany withCString (cmd:args) $ \cstrs ->
111 withArray0 nullPtr cstrs $ \arr -> do
112 status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmd arr)
114 0 -> return ExitSuccess
115 n -> return (ExitFailure n)
117 foreign import ccall unsafe "rawSystem"
118 c_rawSystem :: CString -> Ptr CString -> IO Int
122 -- On Windows, the command line is passed to the operating system as
123 -- a single string. Command-line parsing is done by the executable
125 rawSystem cmd args = do
126 -- NOTE: 'cmd' is assumed to contain the application to run _only_,
127 -- as it'll be quoted surrounded in quotes here.
128 let cmdline = translate cmd ++ concat (map ((' ':) . translate) args)
129 withCString cmdline $ \pcmdline -> do
130 status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmdline)
132 0 -> return ExitSuccess
133 n -> return (ExitFailure n)
135 translate :: String -> String
136 translate str@('"':_) = str -- already escaped.
137 -- ToDo: this case is wrong. It is only here because we
138 -- abuse the system in GHC's SysTools by putting arguments into
139 -- the command name; at some point we should fix it up and remove
141 translate str = '"' : snd (foldr escape (True,"\"") str)
142 where escape '"' (b, str) = (True, '\\' : '"' : str)
143 escape '\\' (True, str) = (True, '\\' : '\\' : str)
144 escape '\\' (False, str) = (False, '\\' : str)
145 escape c (b, str) = (False, c : str)
146 -- See long comment above for what this function is trying to do.
148 -- The Bool passed back along the string is True iff the
149 -- rest of the string is a sequence of backslashes followed by
152 foreign import ccall unsafe "rawSystem"
153 c_rawSystem :: CString -> IO Int