Haskell:
Creating a temporary file

How to:

Haskell provides the temporary package, which includes handy functions for temp file operations. Here’s a quick demo:

import System.IO.Temp (withSystemTempFile)
import System.IO (hPutStrLn, hClose)

main :: IO ()
main = withSystemTempFile "mytemp.txt" $ \tempFilePath tempFileHandle -> do
    -- Write something to the temp file
    hPutStrLn tempFileHandle "Hello, temporary file!"
    -- Close the file (happens automatically too!)
    hClose tempFileHandle
    putStrLn $ "A temporary file was created at: " ++ tempFilePath

Sample output:

A temporary file was created at: /tmp/mytemp.txt123456

Deep Dive

Back in the day, managing temporary files could be a pain and risky for race conditions—two programs trying to make or use the same file. Hence, Haskell’s temporary package was created. It gives you functions like withSystemTempFile, which creates a temp file and automatically gets rid of it when you’re done. Pretty neat for keeping your file operations tight and tidy.

There are alternatives like using the unix package for nitty-gritty file operations, but temporary abstracts away the complexity. When using temporary, file names are unique thanks to internal functions. No two temp files will clash, making your life a bit easier.

The magic in Haskell’s approach includes its functional nature, ensuring that side effects, like file creation, are handled carefully. It leans on its type system and IO monad to manage resources responsibly.

See Also

• System.IO.Temp documentation: Official docs for the temp file functions.
• Real-World Haskell, Chapter 7, I/O: A book section explaining Haskell I/O, which covers temp file creation in more detail.