FilePath

The filepath package provides functionality for manipulating FilePath values, and is shipped with GHC. It provides three modules:

• System.FilePath.Posix manipulates POSIX/Linux style FilePath values (with / as the path separator).
• System.FilePath.Windows manipulates Windows style FilePath values (with either \ or / as the path separator, and deals with drives).
• System.FilePath is an alias for the module appropriate to your platform.

All three modules provide the same API, and the same documentation (calling out differences in the different variants).

What is a FilePath?

In Haskell, the definition is type FilePath = String as of now. A Haskell String is a list of Unicode code points.

On unix, filenames don't have a predefined encoding as per the POSIX specification and are passed as char[] to syscalls.

On windows (at least the API used by Win32) filepaths are UTF-16 strings.

This means that Haskell filepaths have to be converted to C-strings on unix (utilizing the current filesystem encoding) and to UTF-16 strings on windows.

Further, this is a low-level library and it makes no attempt at providing a more type safe variant for filepaths (e.g. by distinguishing between absolute and relative paths) and ensures no invariants (such as filepath validity).

For such libraries, check out the following:

• hpath
• path
• paths
• strong-path