magic

It is a binding to the C libmagic library. It allows you to determine the type of a file not by looking at its name or extension, but rather by examining the contents itself.

libmagic can provide either a textual description or a MIME content type (and, occasionally, also a character set). The Haskell binding can examine files, open file descriptors, and in-memory data (as a strict ByteString). Results come back as Text.

You need the C libmagic library and its development headers installed before building. It is part of the file package.

With cabal:

cabal build
cabal test

With stack:

stack build
stack test

libmagic is located automatically via pkg-config. If pkg-config cannot find it (for example, an unusual install location), point Cabal at the library directly:

cabal build \
  --extra-lib-dirs=/path/to/lib \
  --extra-include-dirs=/path/to/include

Add magic to your build-depends. The easiest way in is Magic.FilePath, which takes ordinary String paths:

import Magic.FilePath          -- convenience facade: ordinary String paths
import qualified Data.Text.IO as T

main :: IO ()
main = do
  magic <- magicOpen MagicMimeType
  magicLoadDefault magic
  mime <- magicFile magic "some-file.png"
  T.putStrLn mime        -- e.g. "image/png"

import Magic is the primary API. It is the same in every way except that paths are OsPath instead of String. Prefer it when filename correctness matters.

Magic.FilePath is a drop-in facade that converts paths through the locale's filesystem encoding (encodeFS / decodeFS). For ordinary ASCII/UTF-8 filenames under a UTF-8 locale that is perfectly fine. What you give up: a String path cannot faithfully represent every path the operating system can. Filenames containing bytes that are not valid in the current locale (raw non-UTF-8 bytes on Unix, names created under a different LANG/LC_*, and so on) may be corrupted or fail to round-trip, so you can fail to open a file that exists, or open the wrong one, and the outcome depends on the environment. OsPath stores the OS-native path bytes verbatim, so it represents any path losslessly and independently of the locale.

magic-haskell was written by John Goerzen jgoerzen@complete.org, who created it in 2005 and maintained it for nearly two decades. It is now maintained by Philippe, with development at https://github.com/philippedev101/magic-haskell.

3-clause BSD. See the COPYING file included with the package.