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module ProcessUtils
( ExitCode(ExitFailure,ExitSuccess)
, systemEnv
) where
import GHC.IO.Exception ( ioException, IOErrorType(..) )
import System.Process
import System.Posix.Signals
import System.Process.Internals (runGenProcess_,defaultSignal)
import System.Environment
import Data.Maybe ( isNothing )
import System.IO.Error ( mkIOError, ioeSetErrorString )
import System.Exit ( ExitCode(..) )
import System.IO
-- | systemEnv
-- This is like System.Process.system except that it lets you set
-- some environment variables.
systemEnv :: [(String, String)] -> String -> IO ExitCode
systemEnv _ "" =
ioException (ioeSetErrorString (mkIOError InvalidArgument "system" Nothing Nothing) "null command")
systemEnv vars cmd = do
env0 <- getEnvironment
let env1 = filter (isNothing . flip lookup vars . fst) env0
env = vars ++ env1
syncProcess "system" $ (shell cmd) {env=Just env}
where
-- This is a non-exported function from System.Process
syncProcess fun c = do
-- The POSIX version of system needs to do some manipulation of signal
-- handlers. Since we're going to be synchronously waiting for the child,
-- we want to ignore ^C in the parent, but handle it the default way
-- in the child (using SIG_DFL isn't really correct, it should be the
-- original signal handler, but the GHC RTS will have already set up
-- its own handler and we don't want to use that).
old_int <- installHandler sigINT Ignore Nothing
old_quit <- installHandler sigQUIT Ignore Nothing
(_,_,_,p) <- runGenProcess_ fun c
(Just defaultSignal) (Just defaultSignal)
r <- waitForProcess p
_ <- installHandler sigINT old_int Nothing
_ <- installHandler sigQUIT old_quit Nothing
return r
-- | readPipe
--
-- This is like System.Process.readProcess but instead of a single
-- command with arguments, you pass it a list which it then executes
-- piping the the output from the prior command into the input for
-- the next command. Like readProcess the next parameter is a string
-- which is sent as input into the initial standard in.
--
-- > readPipe [("grep",["HostConfig"]),("wc",["-l"]) =<< readFile "input"
--
-- is equivalent to shell code:
--
-- > grep HostConfig input | wc -l
--
readPipe :: [(FilePath,[String])] -> String -> IO String
readPipe [(cmd,args)] input = readProcess cmd args input
readPipe ((cmd,args):xs) stdin0 = do
let p = (shell cmd) { std_in = CreatePipe
, std_out = CreatePipe
, std_err = CreatePipe
, cmdspec = RawCommand cmd args
}
(Just sinh,Just sout,Just serr, ph) <- createProcess p
hPutStr sinh stdin0
hClose sinh
readPipe0 xs sout
where
readPipe0 :: [(FilePath,[String])] -> Handle -> IO String
readPipe0 ((cmd,args):xs) stdin0 = do
let p = (shell cmd)
{ std_in = UseHandle stdin0
, std_out = CreatePipe
, std_err = CreatePipe
, cmdspec = RawCommand cmd args
}
(Nothing,Just sout,Just serr, ph) <- createProcess p
readPipe0 xs sout
readPipe0 [] h = hGetContents h
|
