[project @ 2002-07-16 16:08:58 by ross]
[packages/old-locale.git] / System / Environment.hs
1 -----------------------------------------------------------------------------
2 -- |
3 -- Module : System.Environment
4 -- Copyright : (c) The University of Glasgow 2001
5 -- License : BSD-style (see the file libraries/base/LICENSE)
6 --
7 -- Maintainer : libraries@haskell.org
8 -- Stability : provisional
9 -- Portability : portable
10 --
11 -- Miscellaneous information about the system environment.
12 --
13 -----------------------------------------------------------------------------
14
15 module System.Environment
16 (
17 getArgs -- :: IO [String]
18 , getProgName -- :: IO String
19 , getEnv -- :: String -> IO String
20 ) where
21
22 import Prelude
23
24 #ifndef __HUGS__
25 import Foreign
26 import Foreign.C
27 import Control.Monad
28 #endif
29
30 #ifdef __GLASGOW_HASKELL__
31 import GHC.IOBase
32 #endif
33
34 #ifdef __HUGS__
35 import Hugs.System
36 #endif
37
38 -- ---------------------------------------------------------------------------
39 -- getArgs, getProgName, getEnv
40
41 -- Computation `getArgs' returns a list of the program's command
42 -- line arguments (not including the program name).
43
44 #ifndef __HUGS__
45 getArgs :: IO [String]
46 getArgs =
47 alloca $ \ p_argc ->
48 alloca $ \ p_argv -> do
49 getProgArgv p_argc p_argv
50 p <- fromIntegral `liftM` peek p_argc
51 argv <- peek p_argv
52 peekArray (p - 1) (advancePtr argv 1) >>= mapM peekCString
53
54
55 foreign import ccall unsafe "getProgArgv"
56 getProgArgv :: Ptr CInt -> Ptr (Ptr CString) -> IO ()
57
58 {-|
59 Computation 'getProgName' returns the name of the program as it was
60 invoked.
61
62 However, this is hard-to-impossible to implement on some non-Unix
63 OSes, so instead, for maximum portability, we just return the leafname
64 of the program as invoked. Even then there are some differences
65 between platforms: on Windows, for example, a program invoked as foo
66 is probably really @FOO.EXE@, and that is what 'getProgName' will return.
67 -}
68 getProgName :: IO String
69 getProgName =
70 alloca $ \ p_argc ->
71 alloca $ \ p_argv -> do
72 getProgArgv p_argc p_argv
73 argv <- peek p_argv
74 unpackProgName argv
75
76 unpackProgName :: Ptr (Ptr CChar) -> IO String -- argv[0]
77 unpackProgName argv = do
78 s <- peekElemOff argv 0 >>= peekCString
79 return (basename s)
80 where
81 basename :: String -> String
82 basename f = go f f
83 where
84 go acc [] = acc
85 go acc (x:xs)
86 | isPathSeparator x = go xs xs
87 | otherwise = go acc xs
88
89 isPathSeparator :: Char -> Bool
90 isPathSeparator '/' = True
91 #ifdef mingw32_TARGET_OS
92 isPathSeparator '\\' = True
93 #endif
94 isPathSeparator _ = False
95
96
97 -- Computation `getEnv var' returns the value
98 -- of the environment variable {\em var}.
99
100 -- This computation may fail with
101 -- NoSuchThing: The environment variable does not exist.
102
103 getEnv :: String -> IO String
104 getEnv name =
105 withCString name $ \s -> do
106 litstring <- c_getenv s
107 if litstring /= nullPtr
108 then peekCString litstring
109 else ioException (IOError Nothing NoSuchThing "getEnv"
110 "no environment variable" (Just name))
111
112 foreign import ccall unsafe "getenv"
113 c_getenv :: CString -> IO (Ptr CChar)
114 #endif /* __HUGS__ */