System.Console.Shell.ShellMonad

This module implements a monad for use in shell commands and in evaluation functions. It is a state moand layered over IO. liftIO may be used to execute arbitrary I/O actions. However, the shellPut* commands are the preferred way to output text.

The Shell monad

data Sh st a

The type of shell commands. This monad is a state monad layered over IO. The type parameter st allows the monad to carry around a package of user-defined state.

Instances

MonadState st (Sh st)

Monad (Sh st)

Functor (Sh st)

MonadFix (Sh st)

MonadIO (Sh st)

CommandFunction (Sh st ()) st

runSh :: st -> OutputCommand -> Sh st () -> IO (CommandResult st)

Execute a shell action

Output functions

shellPut :: BackendOutput -> Sh st ()

Output a tagged string to the console

shellPutStr :: String -> Sh st ()

Prints a regular output string

shellPutStrLn :: String -> Sh st ()

Prints regular output with a line terminator

shellPutInfo :: String -> Sh st ()

Prints an informational output string

shellPutInfoLn :: String -> Sh st ()

Prints an informational output string with a line terminator

shellPutErr :: String -> Sh st ()

Prints an error output string

shellPutErrLn :: String -> Sh st ()

Prints and error output string with a line terminator

Shell state accessors

getShellSt :: Sh st st

Get the current shell state

putShellSt :: st -> Sh st ()

Set the shell state

modifyShellSt :: (st -> st) -> Sh st ()

Apply the given funtion to the shell state

Special actions

shellSpecial :: ShellSpecial st -> Sh st ()

Schedule a shell "special" action. Only the last call to this function will affect the shell's behavior! It modifies a bit of state that is overwritten on each call.

Extracting and using the shell context

type ShellContext st = (CommandResult st, OutputCommand)

The total context held by the shell, with CommandResult st being mutable and OutputCommand immutable

extractContext :: Sh st (ShellContext st)

Extract the current shell context for future use, see runWithContext

runWithContext :: ShellContext st -> Sh st a -> IO (a, CommandResult st)

Run a shell with the supplied context, useful if you need to invoke a shell within a new IO context, for example when using System.Timeout.timeout

updateCommandResult :: CommandResult st -> Sh st ()

Update the mutable context of this shell