shell.hs

import Data.List
import System.Directory as D
import System.Posix.Signals as S
import System.Posix.Process as P
import System.Posix.Terminal as T


hiddenFile = (== '.') . head

signals = [S.sigTTOU]

ignoreSignal signal = installHandler signal S.Ignore Nothing
defaultSignal signal = installHandler signal S.Default Nothing

ignoreSignals = sequence $ fmap ignoreSignal signals
defaultSignals = sequence $ fmap defaultSignal signals

foregroundProcessGroup = T.setTerminalProcessGroupID 0

foregroundMyself = getProcessGroupID >>= foregroundProcessGroup

waitForProcess = getProcessStatus True True

exec cmd = do
   let bin = head cmd
       args = tail cmd
   P.getProcessID >>= P.createProcessGroupFor >>= foregroundProcessGroup
   defaultSignals
   executeFile bin True args Nothing


setup = ignoreSignals

lsPath' = fmap sort . D.getDirectoryContents
lsPath = fmap (filter $ not.hiddenFile) . lsPath'

ls' = lsPath' "."
ls = lsPath "."

cd = D.setCurrentDirectory

run cmd = do
   pid <- forkProcess $ exec cmd
   pgid <- P.createProcessGroupFor pid
   foregroundProcessGroup pgid
   status <- waitForProcess pid
   foregroundMyself
   return (pid, status)

fg pid = do
   pgid <- P.getProcessGroupIDOf pid
   foregroundProcessGroup pgid
   S.signalProcessGroup S.sigCONT pgid
   status <- waitForProcess pid
   foregroundMyself
   return (pid, status)