|Portability||non-portable (requires libedit)|
This module provides a subset of the functions from
System.Console.Readline, which is distributed in the readline package.
However, because this package links against editline
(http://www.thrysoee.dk/editline/) instead of readline, programs using
this module are not required to be distributed under the GPL.
An example of a typical use of the readline API with history functionality
is illustrated in the following read, eval, print loop:
readEvalPrintLoop :: IO ()
readEvalPrintLoop = do
maybeLine <- readline "% "
case maybeLine of
Nothing -> return () -- EOF / control-d
Just "exit" -> return ()
Just line -> do addHistory line
putStrLn $ "The user input: " ++ (show line)
|-> IO (Maybe String)||returns the line the user input, or Nothing if EOF is encountered.
|readline is similar to System.IO.getLine, but with rich edit
functionality and history capability. readline will read a line
from the terminal and return it, using prompt as a prompt. If
prompt is the empty string, no prompt is issued. The line returned
has the final newline removed, so only the text of the line
remains. A blank line returns the empty string. If EOF is
encountered while reading a line, and the line is empty, Nothing is
returned. If an EOF is read with a non-empty line, it is treated
as a newline.
|Add this command to the history. This allows users to search backward
through history with C-r and step through with up and down arrows, among
|:: FilePath||The file to read.
|-> IO Bool|
|Read in a history file. Returns False on failure
(for example, if the file does not exist).
|:: FilePath||The file to write.
|-> IO Bool|
|Write out a history file. Returns False if there was a problem writing the file.
|Clear the history.
|Stifle the history list, remembering only a certain number of entries.
|Stop stifling the history, returning the previous amount the history was
|Check whether the history is stifled or not. True if stifled, False if not.
|Get the maximum number of history entries, returning 0 if the history is
|Produced by Haddock version 2.4.2|