| MissingH-1.1.0.3: Large utility library | Contents | Index
System.IO.Utils |
Portability | portable
Stability | provisional
Maintainer | John Goerzen <jgoerzen@complete.org>
Contents
Entire File Handle Utilities Opened Handle Data Copying Disk File Data Copying Line Processing Utilities Lazy Interaction Character-based Line-based Misc. Lazy Optimizations
Description
Synopsis
hCopy :: (HVIO a, HVIO b) => a -> b -> IO ()
hCopyProgress :: (HVIO b, HVIO c, Integral a) => b -> c -> (Maybe a -> Integer -> Bool -> IO ()) -> Int -> Maybe a -> IO Integer
hLineCopy :: (HVIO a, HVIO b) => a -> b -> IO ()
lineCopy :: IO ()
copyFileLinesToFile :: FilePath -> FilePath -> IO ()
hPutStrLns :: HVIO a => a -> [String] -> IO ()
hGetLines :: HVIO a => a -> IO [String]
hInteract :: (HVIO a, HVIO b) => a -> b -> (String -> String) -> IO ()
hLineInteract :: (HVIO a, HVIO b) => a -> b -> ([String] -> [String]) -> IO ()
lineInteract :: ([String] -> [String]) -> IO ()
lazyMapM :: (a -> IO b) -> [a] -> IO [b]
optimizeForBatch :: IO ()
optimizeForInteraction :: IO ()
Entire File Handle Utilities
Opened Handle Data Copying
hCopy :: (HVIO a, HVIO b) => a -> b -> IO ()
Copies from one handle to another in raw mode (using hGetContents).
hCopyProgress
:: (HVIO b, HVIO c, Integral a) |
=> b | Input handle
-> c | Output handle
-> (Maybe a -> Integer -> Bool -> IO ()) | Progress function -- the bool is always False unless this is the final call
-> Int |
-> Maybe a |
-> IO Integer |
Copies from one handle to another in raw mode (using hGetContents). Takes a function to provide progress updates to the user.
hLineCopy :: (HVIO a, HVIO b) => a -> b -> IO ()
Copies from one handle to another in text mode (with lines). Like hBlockCopy, this implementation is nice:
     hLineCopy hin hout = hLineInteract hin hout id
lineCopy :: IO ()
Copies from `stdin` to `stdout` using lines. An alias for `hLineCopy` over `stdin` and `stdout`.
Disk File Data Copying
copyFileLinesToFile :: FilePath -> FilePath -> IO ()
Copies one filename to another in text mode. Please note that the Unix permission bits are set at a default; you may need to adjust them after the copy yourself. This function is implemented using `hLineCopy` internally.
Line Processing Utilities
hPutStrLns :: HVIO a => a -> [String] -> IO ()
Given a list of strings, output a line containing each item, adding newlines as appropriate. The list is not expected to have newlines already.
hGetLines :: HVIO a => a -> IO [String]
Given a handle, returns a list of all the lines in that handle. Thanks to lazy evaluation, this list does not have to be read all at once. Combined with `hPutStrLns`, this can make a powerful way to develop filters. See the `lineInteract` function for more on that concept. Example:
     main = do
            l <- hGetLines stdin
            hPutStrLns stdout $ filter (startswith "1") l
Lazy Interaction
Character-based
hInteract :: (HVIO a, HVIO b) => a -> b -> (String -> String) -> IO ()
This is similar to the built-in `interact`, but works on any handle, not just stdin and stdout. In other words:
     interact = hInteract stdin stdout
Line-based
hLineInteract :: (HVIO a, HVIO b) => a -> b -> ([String] -> [String]) -> IO ()
Line-based interaction over arbitrary handles. This is similar to wrapping hInteract with `lines` and `unlines`. One could view this function like this:
     hLineInteract finput foutput func =
         let newf = unlines . func . lines in
             hInteract finput foutput newf
Though the actual implementation is this for efficiency:
     hLineInteract finput foutput func =
         do
         lines <- hGetLines finput
         hPutStrLns foutput (func lines)
lineInteract :: ([String] -> [String]) -> IO ()
Line-based interaction. This is similar to wrapping your interact functions with `lines` and `unlines`. This equality holds:
     lineInteract = hLineInteract stdin stdout
Here's an example:
     main = lineInteract (filter (startswith "1"))
This will act as a simple version of grep -- all lines that start with 1 will be displayed; all others will be ignored.
Misc. Lazy
lazyMapM :: (a -> IO b) -> [a] -> IO [b]
Applies a given function to every item in a list, and returns the new list. Unlike the system's mapM, items are evaluated lazily.
Optimizations
optimizeForBatch :: IO ()
Sets stdin and stdout to be block-buffered. This can save a huge amount of system resources since far fewer syscalls are made, and can make programs run much faster.
optimizeForInteraction :: IO ()
Sets stdin and stdout to be line-buffered. This saves resources on stdout, but not many on stdin, since it it still looking for newlines.
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