System.Terminal

Documentation

data Terminal

Constructors

Terminal

Fields

• termType :: ByteString

  The terminal identification string usually extracted from the environment variable TERM. Should contain values like xterm or `rxvt-unicode`.

• termInput :: STM Event

  A stream of input events. The transaction will succeed as soon as the next input event becomes available.

  Note: Trying to read more than one event within the same transaction might be successfull, but might also lead to undesired behaviour as the transaction will block until all of its preconditions are fulfilled. Some form of orElse needs to be used in a correct way for reading several events at once.

• termOutput :: Text -> STM ()

  This transaction appends a piece of Text to the output buffer. It shall block when the buffer exeeded its capacity and unblock as soon as space becomes available again.

  Note: All implementations must limit the size of the output buffer or the application is at risk of running out of memory when writing much faster than the terminal can read. Using a TMVar as a buffer of size 1 is perfectly fine here.

• termInterrupt :: STM ()

  This transaction succeeds as soon as an interrupt event occurs. Executing the transaction shall reset an interrupt flag maintained by a supervising background thread.

  It is mandatory to regularly check this transaction in order to signal responsiveness to the background thread. The supervisor is otherwise advised to terminate the program as soon as a second interrupt arrives.

  Note: This is a very low-level operation. Operations like waitEvent, waitEventOrElse or waitInterruptOrElse are more convenient and do this automatically.

• termFlush :: STM ()

  This operations flushes the output buffer. Whether it blocks or not until the buffer has actually been flushed shall be undefined (there might be other buffers involved that cannot be force-flushed so it is probably better to not give any guarantees here).

• termScreenSize :: STM (Int, Int)

  This transaction shall return the latest known screen size without blocking. The first parameter denotes the number of rows and the one the number of columns.

• termSpecialChars :: Char -> Maybe Event

withTerminal :: (MonadIO m, MonadMask m) => (Terminal -> m a) -> m a

(Indirection just for upcoming documentation).