Utility that copies all files from source directory that absent in target directory.

gistfile1.hs

module Main (main) where

import System.Environment (getArgs)
import System.Directory (getDirectoryContents, doesFileExist, copyFile)
import Control.Monad (filterM, mapM)
import Data.List

-- Line separator
lineSeparator = "\n"

-- Not proper names
bannedNames = ["..", "."]

-- Info string
usageString = "Usage: [source directory] [target directory]"

-- Function that appends directory name to file's name
appendDirectoryToFileName :: String -> String -> String
appendDirectoryToFileName directory fileName = directory ++ "/" ++ fileName

-- Function that gets only file contents from directory.
getProperFileNames :: String -> IO [FilePath]
getProperFileNames directoryName = do
	directoryContents <- getDirectoryContents directoryName

	let properNames = 
		(filter 
			(\name -> name `notElem` bannedNames) 
			directoryContents)

	filterM (\name -> doesFileExist (appendDirectoryToFileName directoryName name)) properNames

-- Main function
main :: IO ()
main = do
	arguments <- getArgs

	let argsLength = length arguments

	if argsLength == 2 then do
		let sourceDirectoryName = arguments !! 0
		let targetDirectoryName = arguments !! 1
		putStrLn $ "Copying files from: \"" ++ sourceDirectoryName ++ "\" to \"" ++ targetDirectoryName ++ "\""

		properSourceFileNames <- getProperFileNames sourceDirectoryName
		properTargetFileNames <- getProperFileNames targetDirectoryName

		let filesDifference = properSourceFileNames \\ properTargetFileNames
		putStrLn $ foldl (\first second -> first ++ lineSeparator ++ second) "" filesDifference

		copyResults <- mapM 
			(\name -> do
				copyFile
					(appendDirectoryToFileName sourceDirectoryName name)
					(appendDirectoryToFileName targetDirectoryName name)) 
			filesDifference

		putStrLn $ (show $ length copyResults) ++ " files successfuly copied."
	else
		error usageString