split groups of related functions out of Utility

Utility/SafeCommand.hs

@@ -0,0 +1,104 @@
+{- safely running shell commands
+ -
+ - Copyright 2010-2011 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Utility.SafeCommand where
+
+import System.Exit
+import qualified System.Posix.Process
+import System.Posix.Process hiding (executeFile)
+import System.Posix.Signals
+import Data.String.Utils
+import System.Log.Logger
+
+{- A type for parameters passed to a shell command. A command can
+ - be passed either some Params (multiple parameters can be included,
+ - whitespace-separated, or a single Param (for when parameters contain
+ - whitespace), or a File.
+ -}
+data CommandParam = Params String | Param String | File FilePath
+	deriving (Eq, Show, Ord)
+
+{- Used to pass a list of CommandParams to a function that runs
+ - a command and expects Strings. -}
+toCommand :: [CommandParam] -> [String]
+toCommand = (>>= unwrap)
+	where
+		unwrap (Param s) = [s]
+		unwrap (Params s) = filter (not . null) (split " " s)
+		-- Files that start with a dash are modified to avoid
+		-- the command interpreting them as options.
+		unwrap (File s@('-':_)) = ["./" ++ s]
+		unwrap (File s) = [s]
+
+{- Run a system command, and returns True or False
+ - if it succeeded or failed.
+ -
+ - SIGINT(ctrl-c) is allowed to propigate and will terminate the program.
+ -}
+boolSystem :: FilePath -> [CommandParam] -> IO Bool
+boolSystem command params = boolSystemEnv command params Nothing
+
+boolSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO Bool
+boolSystemEnv command params env = do
+	-- Going low-level because all the high-level system functions
+	-- block SIGINT etc. We need to block SIGCHLD, but allow
+	-- SIGINT to do its default program termination.
+	let sigset = addSignal sigCHLD emptySignalSet
+	oldint <- installHandler sigINT Default Nothing
+	oldset <- getSignalMask
+	blockSignals sigset
+	childpid <- forkProcess $ childaction oldint oldset
+	mps <- getProcessStatus True False childpid
+	restoresignals oldint oldset
+	case mps of
+		Just (Exited ExitSuccess) -> return True
+		_ -> return False
+	where
+		restoresignals oldint oldset = do
+			_ <- installHandler sigINT oldint Nothing
+			setSignalMask oldset
+		childaction oldint oldset = do
+			restoresignals oldint oldset
+			executeFile command True (toCommand params) env
+
+{- executeFile with debug logging -}
+executeFile :: FilePath -> Bool -> [String] -> Maybe [(String, String)] -> IO ()
+executeFile c path p e = do
+	debugM "Utility.SafeCommand.executeFile" $
+		"Running: " ++ c ++ " " ++ show p ++ " " ++ maybe "" show e
+	System.Posix.Process.executeFile c path p e
+
+{- Escapes a filename or other parameter to be safely able to be exposed to
+ - the shell. -}
+shellEscape :: String -> String
+shellEscape f = "'" ++ escaped ++ "'"
+	where
+		-- replace ' with '"'"'
+		escaped = join "'\"'\"'" $ split "'" f
+
+{- Unescapes a set of shellEscaped words or filenames. -}
+shellUnEscape :: String -> [String]
+shellUnEscape [] = []
+shellUnEscape s = word : shellUnEscape rest
+	where
+		(word, rest) = findword "" s
+		findword w [] = (w, "")
+		findword w (c:cs)
+			| c == ' ' = (w, cs)
+			| c == '\'' = inquote c w cs
+			| c == '"' = inquote c w cs
+			| otherwise = findword (w++[c]) cs
+		inquote _ w [] = (w, "")
+		inquote q w (c:cs)
+			| c == q = findword w cs
+			| otherwise = inquote q (w++[c]) cs
+
+{- For quickcheck. -}
+prop_idempotent_shellEscape :: String -> Bool
+prop_idempotent_shellEscape s = [s] == (shellUnEscape . shellEscape) s
+prop_idempotent_shellEscape_multiword :: [String] -> Bool
+prop_idempotent_shellEscape_multiword s = s == (shellUnEscape . unwords . map shellEscape) s