Shellac-0.9.5.1: A framework for creating shell envinronments Source code Contents Index

System.Console.Shell.ShellMonad

Contents The Shell monad Output functions Shell state accessors Special actions Extracting and using the shell context

Description

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.

Synopsis

data Sh st a runSh :: st -> OutputCommand -> Sh st () -> IO (CommandResult st) shellPut :: BackendOutput -> Sh st () shellPutStr :: String -> Sh st () shellPutStrLn :: String -> Sh st () shellPutInfo :: String -> Sh st () shellPutInfoLn :: String -> Sh st () shellPutErr :: String -> Sh st () shellPutErrLn :: String -> Sh st () getShellSt :: Sh st st putShellSt :: st -> Sh st () modifyShellSt :: (st -> st) -> Sh st () shellSpecial :: ShellSpecial st -> Sh st () type ShellContext st = (CommandResult st, OutputCommand) extractContext :: Sh st (ShellContext st) runWithContext :: ShellContext st -> Sh st a -> IO (a, CommandResult st) updateCommandResult :: CommandResult st -> Sh st ()

The Shell monad

data Sh st a Source

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) Source

Execute a shell action

Output functions

shellPut :: BackendOutput -> Sh st () Source

Output a tagged string to the console

shellPutStr :: String -> Sh st () Source

Prints a regular output string

shellPutStrLn :: String -> Sh st () Source

Prints regular output with a line terminator

shellPutInfo :: String -> Sh st () Source

Prints an informational output string

shellPutInfoLn :: String -> Sh st () Source

Prints an informational output string with a line terminator

shellPutErr :: String -> Sh st () Source

Prints an error output string

shellPutErrLn :: String -> Sh st () Source

Prints and error output string with a line terminator

Shell state accessors

getShellSt :: Sh st st Source

Get the current shell state

putShellSt :: st -> Sh st () Source

Set the shell state

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

Apply the given funtion to the shell state

Special actions

shellSpecial :: ShellSpecial st -> Sh st () Source

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) Source

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

extractContext :: Sh st (ShellContext st) Source

Extract the current shell context for future use, see runWithContext

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

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 () Source

Update the mutable context of this shell

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