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|
{- safely running shell commands
-
- Copyright 2010-2013 Joey Hess <joey@kitenet.net>
-
- License: BSD-2-clause
-}
module Utility.SafeCommand where
import System.Exit
import Utility.Process
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
|
