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+{- safely running shell commands
+ -
+ - Copyright 2010-2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Utility.SafeCommand where
+
+import System.Exit
+import Utility.Process
+import System.Process (env)
+import Data.String.Utils
+import Control.Applicative
+import System.FilePath
+import Data.Char
+
+{- 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 = concatMap unwrap
+ where
+ unwrap (Param s) = [s]
+ unwrap (Params s) = filter (not . null) (split " " s)
+ -- Files that start with a non-alphanumeric that is not a path
+ -- separator are modified to avoid the command interpreting them as
+ -- options or other special constructs.
+ unwrap (File s@(h:_))
+ | isAlphaNum h || h `elem` pathseps = [s]
+ | otherwise = ["./" ++ s]
+ unwrap (File s) = [s]
+ -- '/' is explicitly included because it's an alternative
+ -- path separator on Windows.
+ pathseps = pathSeparator:"./"
+
+{- Run a system command, and returns True or False
+ - if it succeeded or failed.
+ -}
+boolSystem :: FilePath -> [CommandParam] -> IO Bool
+boolSystem command params = boolSystemEnv command params Nothing
+
+boolSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO Bool
+boolSystemEnv command params environ = dispatch <$> safeSystemEnv command params environ
+ where
+ dispatch ExitSuccess = True
+ dispatch _ = False
+
+{- Runs a system command, returning the exit status. -}
+safeSystem :: FilePath -> [CommandParam] -> IO ExitCode
+safeSystem command params = safeSystemEnv command params Nothing
+
+safeSystemEnv :: FilePath -> [CommandParam] -> Maybe [(String, String)] -> IO ExitCode
+safeSystemEnv command params environ = do
+ (_, _, _, pid) <- createProcess (proc command $ toCommand params)
+ { env = environ }
+ waitForProcess pid
+
+{- Wraps a shell command line inside sh -c, allowing it to be run in a
+ - login shell that may not support POSIX shell, eg csh. -}
+shellWrap :: String -> String
+shellWrap cmdline = "sh -c " ++ shellEscape cmdline
+
+{- Escapes a filename or other parameter to be safely able to be exposed to
+ - the shell.
+ -
+ - This method works for POSIX shells, as well as other shells like csh.
+ -}
+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
+
+{- Segements a list of filenames into groups that are all below the manximum
+ - command-line length limit. Does not preserve order. -}
+segmentXargs :: [FilePath] -> [[FilePath]]
+segmentXargs l = go l [] 0 []
+ where
+ go [] c _ r = c:r
+ go (f:fs) c accumlen r
+ | len < maxlen && newlen > maxlen = go (f:fs) [] 0 (c:r)
+ | otherwise = go fs (f:c) newlen r
+ where
+ len = length f
+ newlen = accumlen + len
+
+ {- 10k of filenames per command, well under Linux's 20k limit;
+ - allows room for other parameters etc. -}
+ maxlen = 10240