1{- safely running shell commands
2 -
3 - Copyright 2010-2015 Joey Hess <id@joeyh.name>
4 -
5 - License: BSD-2-clause
6 -}
7
8{-# OPTIONS_GHC -fno-warn-tabs #-}
9
10module Utility.SafeCommand (
11	CommandParam(..),
12	toCommand,
13	boolSystem,
14	boolSystem',
15	boolSystemEnv,
16	safeSystem,
17	safeSystem',
18	safeSystemEnv,
19	segmentXargsOrdered,
20	segmentXargsUnordered,
21) where
22
23import Utility.Process
24
25import System.Exit
26import System.FilePath
27import Data.Char
28import Data.List
29import Control.Applicative
30import Prelude
31
32-- | Parameters that can be passed to a shell command.
33data CommandParam
34	= Param String -- ^ A parameter
35	| File FilePath -- ^ The name of a file
36	deriving (Eq, Show, Ord)
37
38-- | Used to pass a list of CommandParams to a function that runs
39-- a command and expects Strings. -}
40toCommand :: [CommandParam] -> [String]
41toCommand = map toCommand'
42
43toCommand' :: CommandParam -> String
44toCommand' (Param s) = s
45-- Files that start with a non-alphanumeric that is not a path
46-- separator are modified to avoid the command interpreting them as
47-- options or other special constructs.
48toCommand' (File s@(h:_))
49	| isAlphaNum h || h `elem` pathseps = s
50	| otherwise = "./" ++ s
51  where
52	-- '/' is explicitly included because it's an alternative
53	-- path separator on Windows.
54	pathseps = pathSeparator:"./"
55toCommand' (File s) = s
56
57-- | Run a system command, and returns True or False if it succeeded or failed.
58--
59-- (Throws an exception if the command is not found.)
60--
61-- This and other command running functions in this module log the commands
62-- run at debug level, using System.Log.Logger.
63boolSystem :: FilePath -> [CommandParam] -> IO Bool
64boolSystem command params = boolSystem' command params id
65
66boolSystem' :: FilePath -> [CommandParam] -> (CreateProcess -> CreateProcess) -> IO Bool
67boolSystem' command params mkprocess = dispatch <$> safeSystem' command params mkprocess
68  where
69	dispatch ExitSuccess = True
70	dispatch _ = False
71
72boolSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO Bool
73boolSystemEnv command params environ = boolSystem' command params $
74	\p -> p { env = environ }
75
76-- | Runs a system command, returning the exit status.
77safeSystem :: FilePath -> [CommandParam] -> IO ExitCode
78safeSystem command params = safeSystem' command params id
79
80safeSystem' :: FilePath -> [CommandParam] -> (CreateProcess -> CreateProcess) -> IO ExitCode
81safeSystem' command params mkprocess =
82	withCreateProcess p $ \_ _ _ pid ->
83		waitForProcess pid
84  where
85	p = mkprocess $ proc command (toCommand params)
86
87safeSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO ExitCode
88safeSystemEnv command params environ = safeSystem' command params $
89	\p -> p { env = environ }
90
91-- | Segments a list of filenames into groups that are all below the maximum
92--  command-line length limit.
93segmentXargsOrdered :: [FilePath] -> [[FilePath]]
94segmentXargsOrdered = reverse . map reverse . segmentXargsUnordered
95
96-- | Not preserving order is a little faster, and streams better when
97-- there are a great many filenames.
98segmentXargsUnordered :: [FilePath] -> [[FilePath]]
99segmentXargsUnordered l = go l [] 0 []
100  where
101	go [] c _ r = (c:r)
102	go (f:fs) c accumlen r
103		| newlen > maxlen && len < maxlen = go (f:fs) [] 0 (c:r)
104		| otherwise = go fs (f:c) newlen r
105	  where
106		len = length f
107		newlen = accumlen + len
108
109	{- 10k of filenames per command, well under 100k limit
110	 - of Linux (and OSX has a similar limit);
111	 - allows room for other parameters etc. Also allows for
112	 - eg, multibyte characters. -}
113	maxlen = 10240
114