1 -----------------------------------------------------------------------------
4 -- Copyright : (c) The University of Glasgow 2001
5 -- License : BSD-style (see the file libraries/base/LICENSE)
7 -- Maintainer : libraries@haskell.org
8 -- Stability : provisional
9 -- Portability : portable
11 -- Executing an external command.
13 -----------------------------------------------------------------------------
16 ( system, -- :: String -> IO ExitCode
17 #ifdef __GLASGOW_HASKELL__
18 rawSystem, -- :: FilePath -> [String] -> IO ExitCode
24 #ifdef __GLASGOW_HASKELL__
37 import System (system)
40 -- ---------------------------------------------------------------------------
44 Computation @system cmd@ returns the exit code
45 produced when the operating system processes the command @cmd@.
47 This computation may fail with
49 * @PermissionDenied@: The process has insufficient privileges to
50 perform the operation.
52 * @ResourceExhausted@: Insufficient resources are available to
53 perform the operation.
55 * @UnsupportedOperation@: The implementation does not support
58 On Windows, 'system' is implemented using Windows's native system
59 call, which ignores the @SHELL@ environment variable, and always
60 passes the command to the Windows command interpreter (@CMD.EXE@ or
61 @COMMAND.COM@), hence Unixy shell tricks will not work.
63 #ifdef __GLASGOW_HASKELL__
64 system :: String -> IO ExitCode
65 system "" = ioException (IOError Nothing InvalidArgument "system" "null command" Nothing)
67 withCString cmd $ \s -> do
68 status <- throwErrnoIfMinus1 "system" (primSystem s)
70 0 -> return ExitSuccess
71 n -> return (ExitFailure n)
73 foreign import ccall unsafe "systemCmd" primSystem :: CString -> IO Int
76 ------------------------------------------------------------------------
80 ------------------------------------------------------------------------
83 The computation @rawSystem cmd args@ runs the operating system command
84 whose file name is @cmd@, passing it the arguments @args@. It
85 bypasses the shell, so that @cmd@ should see precisely the argument
86 strings @args@, with no funny escaping or shell meta-syntax expansion.
87 (Unix users will recognise this behaviour
88 as @execvp@, and indeed that's how it's implemented.)
89 It will therefore behave more portably between operating systems than @system@.
91 The return codes are the same as for @system@.
94 rawSystem :: FilePath -> [String] -> IO ExitCode
96 {- -------------------------------------------------------------------------
97 IMPORTANT IMPLEMENTATION NOTES
98 (see also libraries/base/cbits/rawSystem.c)
100 On Unix, rawSystem is easy to implement: use execvp.
102 On Windows it's more tricky. We use CreateProcess, passing a single
103 command-line string (lpCommandLine) as its argument. (CreateProcess
104 is well documented on http://msdn.microsoft/com.)
106 - It parses the beginning of the string to find the command. If the
107 file name has embedded spaces, it must be quoted, using double
109 "foo\this that\cmd" arg1 arg2
111 - The invoked command can in turn access the entire lpCommandLine string,
112 and the C runtime does indeed do so, parsing it to generate the
113 traditional argument vector argv[0], argv[1], etc. It does this
114 using a complex and arcane set of rules which are described here:
116 http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/progs_12.asp
118 (if this URL stops working, you might be able to find it by
119 searching for "Parsing C Command-Line Arguments" on MSDN. Also,
120 the code in the Microsoft C runtime that does this translation
121 is shipped with VC++).
124 Our goal in rawSystem is to take a command filename and list of
125 arguments, and construct a string which inverts the translatsions
126 described above, such that the program at the other end sees exactly
127 the same arguments in its argv[] that we passed to rawSystem.
129 This inverse translation is implemented by 'translate' below.
131 Here are some pages that give informations on Windows-related
132 limitations and deviations from Unix conventions:
134 http://support.microsoft.com/default.aspx?scid=kb;en-us;830473
135 Command lines and environment variables effectively limited to 8191
136 characters on Win XP, 2047 on NT/2000 (probably even less on Win 9x):
138 http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/percent.asp
139 Command-line substitution under Windows XP. IIRC these facilities (or at
140 least a large subset of them) are available on Win NT and 2000. Some
141 might be available on Win 9x.
143 http://www.microsoft.com/windowsxp/home/using/productdoc/en/default.asp?url=/WINDOWSXP/home/using/productdoc/en/Cmd.asp
144 How CMD.EXE processes command lines.
147 Note: CreateProcess does have a separate argument (lpApplicationName)
148 with which you can specify the command, but we have to slap the
149 command into lpCommandLine anyway, so that argv[0] is what a C program
150 expects (namely the application name). So it seems simpler to just
151 use lpCommandLine alone, which CreateProcess supports.
153 ----------------------------------------------------------------------------- -}
155 #ifndef mingw32_TARGET_OS
158 withCString cmd $ \pcmd ->
159 withMany withCString (cmd:args) $ \cstrs ->
160 withArray0 nullPtr cstrs $ \arr -> do
161 status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmd arr)
163 0 -> return ExitSuccess
164 n -> return (ExitFailure n)
166 foreign import ccall unsafe "rawSystem"
167 c_rawSystem :: CString -> Ptr CString -> IO Int
171 -- On Windows, the command line is passed to the operating system as
172 -- a single string. Command-line parsing is done by the executable
174 rawSystem cmd args = do
175 -- NOTE: 'cmd' is assumed to contain the application to run _only_,
176 -- as it'll be quoted surrounded in quotes here.
177 let cmdline = translate cmd ++ concat (map ((' ':) . translate) args)
178 withCString cmdline $ \pcmdline -> do
179 status <- throwErrnoIfMinus1 "rawSystem" (c_rawSystem pcmdline)
181 0 -> return ExitSuccess
182 n -> return (ExitFailure n)
184 translate :: String -> String
185 translate str@('"':_) = str -- already escaped.
186 -- ToDo: this case is wrong. It is only here because we
187 -- abuse the system in GHC's SysTools by putting arguments into
188 -- the command name; at some point we should fix it up and remove
190 translate str = '"' : snd (foldr escape (True,"\"") str)
191 where escape '"' (b, str) = (True, '\\' : '"' : str)
192 escape '\\' (True, str) = (True, '\\' : '\\' : str)
193 escape '\\' (False, str) = (False, '\\' : str)
194 escape c (b, str) = (False, c : str)
195 -- See long comment above for what this function is trying to do.
197 -- The Bool passed back along the string is True iff the
198 -- rest of the string is a sequence of backslashes followed by
201 foreign import ccall unsafe "rawSystem"
202 c_rawSystem :: CString -> IO Int
206 #endif /* __GLASGOW_HASKELL__ */