1 ------------------------------------------------------------------------
5 -- This is a separate file #included into Haskell source, because
6 -- we use it in a few places in the GHC source tree.
8 ------------------------------------------------------------------------
11 The computation @'rawSystem' cmd args@ runs the operating system command
12 whose file name is @cmd@, passing it the arguments @args@. It
13 bypasses the shell, so that @cmd@ should see precisely the argument
14 strings @args@, with no funny escaping or shell meta-syntax expansion.
15 (Unix users will recognise this behaviour
16 as @execvp@, and indeed that's how it's implemented.)
17 It will therefore behave more portably between operating systems than 'system'.
19 The return codes are the same as for 'system'.
22 rawSystem :: FilePath -> [String] -> IO ExitCode
24 {- -------------------------------------------------------------------------
25 IMPORTANT IMPLEMENTATION NOTES
26 (see also libraries/base/cbits/rawSystem.c)
28 On Unix, rawSystem is easy to implement: use execvp.
30 On Windows it's more tricky. We use CreateProcess, passing a single
31 command-line string (lpCommandLine) as its argument. (CreateProcess
32 is well documented on http://msdn.microsoft/com.)
34 - It parses the beginning of the string to find the command. If the
35 file name has embedded spaces, it must be quoted, using double
37 "foo\this that\cmd" arg1 arg2
39 - The invoked command can in turn access the entire lpCommandLine string,
40 and the C runtime does indeed do so, parsing it to generate the
41 traditional argument vector argv[0], argv[1], etc. It does this
42 using a complex and arcane set of rules which are described here:
44 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/progs_12.asp
46 (if this URL stops working, you might be able to find it by
47 searching for "Parsing C Command-Line Arguments" on MSDN. Also,
48 the code in the Microsoft C runtime that does this translation
49 is shipped with VC++).
52 Our goal in rawSystem is to take a command filename and list of
53 arguments, and construct a string which inverts the translatsions
54 described above, such that the program at the other end sees exactly
55 the same arguments in its argv[] that we passed to rawSystem.
57 This inverse translation is implemented by 'translate' below.
59 Here are some pages that give informations on Windows-related
60 limitations and deviations from Unix conventions:
62 http://support.microsoft.com/default.aspx?scid=kb;en-us;830473
63 Command lines and environment variables effectively limited to 8191
64 characters on Win XP, 2047 on NT/2000 (probably even less on Win 9x):
66 http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/percent.asp
67 Command-line substitution under Windows XP. IIRC these facilities (or at
68 least a large subset of them) are available on Win NT and 2000. Some
69 might be available on Win 9x.
71 http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/Cmd.asp
72 How CMD.EXE processes command lines.
75 Note: CreateProcess does have a separate argument (lpApplicationName)
76 with which you can specify the command, but we have to slap the
77 command into lpCommandLine anyway, so that argv[0] is what a C program
78 expects (namely the application name). So it seems simpler to just
79 use lpCommandLine alone, which CreateProcess supports.
81 ----------------------------------------------------------------------------- -}
83 #ifndef mingw32_TARGET_OS
86 withCString cmd $ \pcmd ->
87 withMany withCString (cmd:args) $ \cstrs ->
88 withArray0 nullPtr cstrs $ \arr -> do
89 status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmd arr)
91 0 -> return ExitSuccess
92 n -> return (ExitFailure n)
94 foreign import ccall unsafe "rawSystem"
95 c_rawSystem :: CString -> Ptr CString -> IO Int
99 -- On Windows, the command line is passed to the operating system as
100 -- a single string. Command-line parsing is done by the executable
102 rawSystem cmd args = do
103 -- NOTE: 'cmd' is assumed to contain the application to run _only_,
104 -- as it'll be quoted surrounded in quotes here.
105 let cmdline = translate cmd ++ concat (map ((' ':) . translate) args)
106 withCString cmdline $ \pcmdline -> do
107 status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmdline)
109 0 -> return ExitSuccess
110 n -> return (ExitFailure n)
112 translate :: String -> String
113 translate str@('"':_) = str -- already escaped.
114 -- ToDo: this case is wrong. It is only here because we
115 -- abuse the system in GHC's SysTools by putting arguments into
116 -- the command name; at some point we should fix it up and remove
118 translate str = '"' : snd (foldr escape (True,"\"") str)
119 where escape '"' (b, str) = (True, '\\' : '"' : str)
120 escape '\\' (True, str) = (True, '\\' : '\\' : str)
121 escape '\\' (False, str) = (False, '\\' : str)
122 escape c (b, str) = (False, c : str)
123 -- See long comment above for what this function is trying to do.
125 -- The Bool passed back along the string is True iff the
126 -- rest of the string is a sequence of backslashes followed by
129 foreign import ccall unsafe "rawSystem"
130 c_rawSystem :: CString -> IO Int