propellor/src/Utility/Process.hs

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{- System.Process enhancements, including additional ways of running
- processes, and logging.
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
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- License: BSD-2-clause
-}
{-# LANGUAGE CPP, Rank2Types #-}
module Utility.Process (
module X,
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CreateProcess(..),
StdHandle(..),
readProcess,
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readProcess',
readProcessEnv,
writeReadProcessEnv,
forceSuccessProcess,
checkSuccessProcess,
ignoreFailureProcess,
createProcessSuccess,
createProcessChecked,
createBackgroundProcess,
processTranscript,
processTranscript',
withHandle,
withBothHandles,
withQuietOutput,
createProcess,
startInteractiveProcess,
stdinHandle,
stdoutHandle,
stderrHandle,
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bothHandles,
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processHandle,
devNull,
) where
import qualified System.Process
import System.Process as X hiding (CreateProcess(..), createProcess, runInteractiveProcess, readProcess, readProcessWithExitCode, system, rawSystem, runInteractiveCommand, runProcess)
import System.Process hiding (createProcess, readProcess)
import System.Exit
import System.IO
import System.Log.Logger
import Control.Concurrent
import qualified Control.Exception as E
import Control.Monad
#ifndef mingw32_HOST_OS
import System.Posix.IO
#else
import Control.Applicative
#endif
import Data.Maybe
import Utility.Misc
import Utility.Exception
type CreateProcessRunner = forall a. CreateProcess -> ((Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> IO a) -> IO a
data StdHandle = StdinHandle | StdoutHandle | StderrHandle
deriving (Eq)
{- Normally, when reading from a process, it does not need to be fed any
- standard input. -}
readProcess :: FilePath -> [String] -> IO String
readProcess cmd args = readProcessEnv cmd args Nothing
readProcessEnv :: FilePath -> [String] -> Maybe [(String, String)] -> IO String
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readProcessEnv cmd args environ = readProcess' p
where
p = (proc cmd args)
{ std_out = CreatePipe
, env = environ
}
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readProcess' :: CreateProcess -> IO String
readProcess' p = withHandle StdoutHandle createProcessSuccess p $ \h -> do
output <- hGetContentsStrict h
hClose h
return output
{- Runs an action to write to a process on its stdin,
- returns its output, and also allows specifying the environment.
-}
writeReadProcessEnv
:: FilePath
-> [String]
-> Maybe [(String, String)]
-> (Maybe (Handle -> IO ()))
-> (Maybe (Handle -> IO ()))
-> IO String
writeReadProcessEnv cmd args environ writestdin adjusthandle = do
(Just inh, Just outh, _, pid) <- createProcess p
maybe (return ()) (\a -> a inh) adjusthandle
maybe (return ()) (\a -> a outh) adjusthandle
-- fork off a thread to start consuming the output
output <- hGetContents outh
outMVar <- newEmptyMVar
_ <- forkIO $ E.evaluate (length output) >> putMVar outMVar ()
-- now write and flush any input
maybe (return ()) (\a -> a inh >> hFlush inh) writestdin
hClose inh -- done with stdin
-- wait on the output
takeMVar outMVar
hClose outh
-- wait on the process
forceSuccessProcess p pid
return output
where
p = (proc cmd args)
{ std_in = CreatePipe
, std_out = CreatePipe
, std_err = Inherit
, env = environ
}
{- Waits for a ProcessHandle, and throws an IOError if the process
- did not exit successfully. -}
forceSuccessProcess :: CreateProcess -> ProcessHandle -> IO ()
forceSuccessProcess p pid = do
code <- waitForProcess pid
case code of
ExitSuccess -> return ()
ExitFailure n -> fail $ showCmd p ++ " exited " ++ show n
{- Waits for a ProcessHandle and returns True if it exited successfully.
- Note that using this with createProcessChecked will throw away
- the Bool, and is only useful to ignore the exit code of a process,
- while still waiting for it. -}
checkSuccessProcess :: ProcessHandle -> IO Bool
checkSuccessProcess pid = do
code <- waitForProcess pid
return $ code == ExitSuccess
ignoreFailureProcess :: ProcessHandle -> IO Bool
ignoreFailureProcess pid = do
void $ waitForProcess pid
return True
{- Runs createProcess, then an action on its handles, and then
- forceSuccessProcess. -}
createProcessSuccess :: CreateProcessRunner
createProcessSuccess p a = createProcessChecked (forceSuccessProcess p) p a
{- Runs createProcess, then an action on its handles, and then
- a checker action on its exit code, which must wait for the process. -}
createProcessChecked :: (ProcessHandle -> IO b) -> CreateProcessRunner
createProcessChecked checker p a = do
t@(_, _, _, pid) <- createProcess p
r <- tryNonAsync $ a t
_ <- checker pid
either E.throw return r
{- Leaves the process running, suitable for lazy streaming.
- Note: Zombies will result, and must be waited on. -}
createBackgroundProcess :: CreateProcessRunner
createBackgroundProcess p a = a =<< createProcess p
{- Runs a process, optionally feeding it some input, and
- returns a transcript combining its stdout and stderr, and
- whether it succeeded or failed. -}
processTranscript :: String -> [String] -> (Maybe String) -> IO (String, Bool)
processTranscript cmd opts input = processTranscript' cmd opts Nothing input
processTranscript' :: String -> [String] -> Maybe [(String, String)] -> (Maybe String) -> IO (String, Bool)
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processTranscript' cmd opts environ input = do
#ifndef mingw32_HOST_OS
{- This implementation interleves stdout and stderr in exactly the order
- the process writes them. -}
(readf, writef) <- createPipe
readh <- fdToHandle readf
writeh <- fdToHandle writef
p@(_, _, _, pid) <- createProcess $
(proc cmd opts)
{ std_in = if isJust input then CreatePipe else Inherit
, std_out = UseHandle writeh
, std_err = UseHandle writeh
, env = environ
}
hClose writeh
get <- mkreader readh
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writeinput input p
transcript <- get
ok <- checkSuccessProcess pid
return (transcript, ok)
#else
{- This implementation for Windows puts stderr after stdout. -}
p@(_, _, _, pid) <- createProcess $
(proc cmd opts)
{ std_in = if isJust input then CreatePipe else Inherit
, std_out = CreatePipe
, std_err = CreatePipe
, env = environ
}
getout <- mkreader (stdoutHandle p)
geterr <- mkreader (stderrHandle p)
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writeinput input p
transcript <- (++) <$> getout <*> geterr
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ok <- checkSuccessProcess pid
return (transcript, ok)
#endif
where
mkreader h = do
s <- hGetContents h
v <- newEmptyMVar
void $ forkIO $ do
void $ E.evaluate (length s)
putMVar v ()
return $ do
takeMVar v
return s
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writeinput (Just s) p = do
let inh = stdinHandle p
unless (null s) $ do
hPutStr inh s
hFlush inh
hClose inh
writeinput Nothing _ = return ()
{- Runs a CreateProcessRunner, on a CreateProcess structure, that
- is adjusted to pipe only from/to a single StdHandle, and passes
- the resulting Handle to an action. -}
withHandle
:: StdHandle
-> CreateProcessRunner
-> CreateProcess
-> (Handle -> IO a)
-> IO a
withHandle h creator p a = creator p' $ a . select
where
base = p
{ std_in = Inherit
, std_out = Inherit
, std_err = Inherit
}
(select, p')
| h == StdinHandle =
(stdinHandle, base { std_in = CreatePipe })
| h == StdoutHandle =
(stdoutHandle, base { std_out = CreatePipe })
| h == StderrHandle =
(stderrHandle, base { std_err = CreatePipe })
{- Like withHandle, but passes (stdin, stdout) handles to the action. -}
withBothHandles
:: CreateProcessRunner
-> CreateProcess
-> ((Handle, Handle) -> IO a)
-> IO a
withBothHandles creator p a = creator p' $ a . bothHandles
where
p' = p
{ std_in = CreatePipe
, std_out = CreatePipe
, std_err = Inherit
}
{- Forces the CreateProcessRunner to run quietly;
- both stdout and stderr are discarded. -}
withQuietOutput
:: CreateProcessRunner
-> CreateProcess
-> IO ()
withQuietOutput creator p = withFile devNull WriteMode $ \nullh -> do
let p' = p
{ std_out = UseHandle nullh
, std_err = UseHandle nullh
}
creator p' $ const $ return ()
devNull :: FilePath
#ifndef mingw32_HOST_OS
devNull = "/dev/null"
#else
devNull = "NUL"
#endif
{- Extract a desired handle from createProcess's tuple.
- These partial functions are safe as long as createProcess is run
- with appropriate parameters to set up the desired handle.
- Get it wrong and the runtime crash will always happen, so should be
- easily noticed. -}
type HandleExtractor = (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> Handle
stdinHandle :: HandleExtractor
stdinHandle (Just h, _, _, _) = h
stdinHandle _ = error "expected stdinHandle"
stdoutHandle :: HandleExtractor
stdoutHandle (_, Just h, _, _) = h
stdoutHandle _ = error "expected stdoutHandle"
stderrHandle :: HandleExtractor
stderrHandle (_, _, Just h, _) = h
stderrHandle _ = error "expected stderrHandle"
bothHandles :: (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> (Handle, Handle)
bothHandles (Just hin, Just hout, _, _) = (hin, hout)
bothHandles _ = error "expected bothHandles"
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processHandle :: (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> ProcessHandle
processHandle (_, _, _, pid) = pid
{- Debugging trace for a CreateProcess. -}
debugProcess :: CreateProcess -> IO ()
debugProcess p = do
debugM "Utility.Process" $ unwords
[ action ++ ":"
, showCmd p
]
where
action
| piped (std_in p) && piped (std_out p) = "chat"
| piped (std_in p) = "feed"
| piped (std_out p) = "read"
| otherwise = "call"
piped Inherit = False
piped _ = True
{- Shows the command that a CreateProcess will run. -}
showCmd :: CreateProcess -> String
showCmd = go . cmdspec
where
go (ShellCommand s) = s
go (RawCommand c ps) = c ++ " " ++ show ps
{- Starts an interactive process. Unlike runInteractiveProcess in
- System.Process, stderr is inherited. -}
startInteractiveProcess
:: FilePath
-> [String]
-> Maybe [(String, String)]
-> IO (ProcessHandle, Handle, Handle)
startInteractiveProcess cmd args environ = do
let p = (proc cmd args)
{ std_in = CreatePipe
, std_out = CreatePipe
, std_err = Inherit
, env = environ
}
(Just from, Just to, _, pid) <- createProcess p
return (pid, to, from)
{- Wrapper around System.Process function that does debug logging. -}
createProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
createProcess p = do
debugProcess p
System.Process.createProcess p