[project @ 2005-01-28 13:36:25 by simonmar]

[ghc-base.git] / System / Cmd.hs

diff --git a/System/Cmd.hs b/System/Cmd.hs
index 0be8008..cf1dc5b 100644 (file)
--- a/System/Cmd.hs
+++ b/System/Cmd.hs
@@ -8,44 +8,91 @@
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- Executing a command.
+-- Executing an external command.
 --
 -----------------------------------------------------------------------------
 
 module System.Cmd
-    ( system        -- :: String -> IO ExitCode
+    ( system,        -- :: String -> IO ExitCode
+      rawSystem,     -- :: FilePath -> [String] -> IO ExitCode
     ) where
 
 import Prelude
 
-import System.Exit
-import Foreign.C
+import System.Exit     ( ExitCode )
 
 #ifdef __GLASGOW_HASKELL__
-import GHC.IOBase
+import System.Process
+import GHC.IOBase      ( ioException, IOException(..), IOErrorType(..) )
+#endif
+
+#ifdef __HUGS__
+import Hugs.System
+#endif
+
+#ifdef __NHC__
+import System (system)
 #endif
 
 -- ---------------------------------------------------------------------------
 -- system
 
--- Computation `system cmd' returns the exit code
--- produced when the operating system processes the command `cmd'.
+{-| 
+Computation @system cmd@ returns the exit code
+produced when the operating system processes the command @cmd@.
+
+This computation may fail with
+
+   * @PermissionDenied@: The process has insufficient privileges to
+     perform the operation.
 
--- This computation may fail with
---   PermissionDenied 
---     The process has insufficient privileges to perform the operation.
---   ResourceExhausted
---      Insufficient resources are available to perform the operation.  
---   UnsupportedOperation
---     The implementation does not support system calls.
+   * @ResourceExhausted@: Insufficient resources are available to
+     perform the operation.
 
+   * @UnsupportedOperation@: The implementation does not support
+     system calls.
+
+On Windows, 'system' is implemented using Windows's native system
+call, which ignores the @SHELL@ environment variable, and always
+passes the command to the Windows command interpreter (@CMD.EXE@ or
+@COMMAND.COM@), hence Unixy shell tricks will not work.
+-}
+#ifdef __GLASGOW_HASKELL__
 system :: String -> IO ExitCode
 system "" = ioException (IOError Nothing InvalidArgument "system" "null command" Nothing)
-system cmd =
-  withCString cmd $ \s -> do
-    status <- throwErrnoIfMinus1 "system" (primSystem s)
-    case status of
-        0  -> return ExitSuccess
-        n  -> return (ExitFailure n)
-
-foreign import ccall unsafe "systemCmd" primSystem :: CString -> IO Int
+system cmd = do
+  p <- runCommand cmd
+  waitForProcess p
+#endif  /* __GLASGOW_HASKELL__ */
+
+{-|
+The computation @'rawSystem' cmd args@ runs the operating system command
+@cmd@ in such a way that it receives as arguments the @args@ strings
+exactly as given, with no funny escaping or shell meta-syntax expansion.
+It will therefore behave more portably between operating systems than 'system'.
+
+The return codes and possible failures are the same as for 'system'.
+-}
+rawSystem :: String -> [String] -> IO ExitCode
+#ifdef __GLASGOW_HASKELL__
+rawSystem cmd args = do
+  p <- runProcess cmd args Nothing Nothing Nothing Nothing Nothing
+  waitForProcess p
+#else /* ! __GLASGOW_HASKELL__ */
+-- crude fallback implementation: could do much better than this under Unix
+rawSystem cmd args = system (unwords (map translate (cmd:args)))
+
+translate :: String -> String
+#if defined(mingw32_HOST_OS)
+-- copied from System.Process (qv)
+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)
+#else /* ! mingw32_HOST_OS */
+translate str = '\'' : foldr escape "'" str
+  where        escape '\'' cs = '\'' : '\\' : '\'' : '\'' : cs
+       escape c    cs = c : cs
+#endif /* ! mingw32_HOST_OS */
+#endif /* ! __GLASGOW_HASKELL__ */