View Category
Files
Reading

Read the contents of a file into a string

haskell
readFile "c:/tmp/myFile.txt"
csharp
string contents = System.IO.File.ReadAllText("filename.txt");

Process a file one line at a time

Open the source file to your solution and print each line in the file, prefixed by the line number, like:
1> First line of file
2> Second line of file
3> Third line of file
haskell
import Data.List

prefixWithNumber str n = show n ++ "> " ++ str

numberStrings (x:xs) n = prefixWithNumber x n : (numberStrings xs (n+1))
numberStrings [] n = []

main = do
str <- readFile "prefix.hs"
putStrLn (intercalate "\n" (numberStrings (lines str) 1))
prefix n str = show n ++ "> " ++ str

main = readFile "prefix.hs" >>=
putStr . unlines . zipWith prefix [1..] . lines
csharp
int counter = 0;

// If the file is large, you would want to buffer this instead of reading everything at once
foreach (string line in System.IO.File.ReadAllLines("filename.txt"))
{
Console.WriteLine("{0}> {1}", ++counter, line);
}
Writing

Write a string to a file

haskell
writeFile "filename" "stringe"
csharp
System.IO.File.WriteAllText("filename.txt", "Some text to write to the file");

Append to a file

haskell
appendfile "filename" "string"
csharp
System.IO.File.AppendAllText("filename.txt", "Some text to append to the file");
Directories

Process each file in a directory

haskell
import System.Directory
import Control.Monad

process filename = putStrLn filename

main = getDirectoryContents "." >>=
filterM doesFileExist >>=
mapM_ process
csharp
foreach (string filename in System.IO.Directory.GetFiles(directory)) ProcessFile(filename);

Process each file in a directory recursively

haskell
import System.Directory (doesFileExist, getDirectoryContents)
import System.FilePath ((</>))

process :: FilePath -> IO ()
process filename = putStrLn filename

mapDir :: (FilePath -> IO ()) -> FilePath -> IO ()
mapDir proc fp = do
isFile <- doesFileExist fp -- is a file of fp
if isFile then proc fp -- process the file
else getDirectoryContents fp >>=
mapM_ (mapDir proc . (fp </>)) . filter (`notElem` [".", ".."])

main = mapDir process "."