diff --git a/ChangeLog.md b/ChangeLog.md
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+++ b/ChangeLog.md
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+# Changelog for polysemy-fs
+
+## v0.1.0.0
+
+* Small filesystem effects for polysemy.
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
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+Copyright Daniel Firth (c) 2020
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Daniel Firth nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
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+# polysemy-fs
+
+This package offers small filesystem effects for polysemy, such as:
+
+```
+data FSExist m a where
+  DoesFileExist :: Path b File -> FSExist m Bool
+  DoesDirExist  :: Path b Dir  -> FSExist m Bool
+```
+
+It should be noted that these are very weak semantic abstractions, as it does
+not provide a way to speak to the filesystem as a whole, and therefore is
+somewhat unsuitable for mocking. These effects exist primarily to give
+interpreters a way to be precise in the type of filesystem operations they use,
+and should be treated in the same way as `Embed IO` in that regard. However, if
+you need a quick fix - then using this directly in application code is a slight
+improvement over using `Embed IO` directly.
+
+Using these as very low level compilation units allows you to inject debugging
+everywhere you use a filesystem operation. For example, using [co-log-polysemy](https://hackage.haskell.org/package/co-log-polysemy) we can do this:
+
+```
+data FileExists where
+  FileExists    :: Path b File -> FileExists
+  FileNotExists :: Path b File -> FileExists
+
+data DirExists where
+  DirExists    :: Path b Dir -> DirExists
+  DirNotExists :: Path b Dir -> DirExists
+
+logFileExists :: Members '[FSExist, Log FileExists] r => Sem r a -> Sem r a
+logFileExists = intercept \case
+  DoesFileExist x -> do
+    z <- doesFileExist x
+    case z of
+      True  -> log $ FileExists x
+      False -> log $ FileNotExists x
+    return z
+  DoesDirExist x -> doesDirExist x
+
+logDirExists :: Members '[FSExist, Log DirExists] r => Sem r a -> Sem r a
+logDirExists = intercept \case
+  DoesDirExist x  -> do
+    z <- doesDirExist x
+    case z of
+      True  -> log $ DirExists x
+      False -> log $ DirNotExists x
+    return z
+  DoesFileExist x -> doesFileExist x
+```
+
+For a look at a unified version of filesystem operations, check out [polysemy-fskvstore](https://hackage.haskell.org/package/fskv-store)
diff --git a/polysemy-fs.cabal b/polysemy-fs.cabal
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--- /dev/null
+++ b/polysemy-fs.cabal
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+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.34.2.
+--
+-- see: https://github.com/sol/hpack
+
+name:           polysemy-fs
+version:        0.1.0.0
+synopsis:       Low level filesystem operations for polysemy.
+category:       Polysemy Filesystem
+author:         Daniel Firth
+maintainer:     dan.firth@homotopic.tech
+copyright:      dan.firth@homotopic.tech
+license:        BSD3
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    README.md
+    ChangeLog.md
+
+source-repository head
+  type: git
+  location: https://gitlab.com/homotopic-tech/polysemy-fs
+
+library
+  exposed-modules:
+      Polysemy.FS
+  other-modules:
+      Paths_polysemy_fs
+  hs-source-dirs:
+      src
+  build-depends:
+      base >=4.7 && <5
+    , bytestring
+    , path
+    , polysemy
+    , rio
+    , temporary
+    , text
+    , unliftio-path
+  default-language: Haskell2010
diff --git a/src/Polysemy/FS.hs b/src/Polysemy/FS.hs
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+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE DataKinds      #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE GADTs          #-}
+{-# LANGUAGE LambdaCase     #-}
+{-# LANGUAGE PolyKinds      #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeOperators  #-}
+module Polysemy.FS where
+
+import Polysemy
+import qualified UnliftIO.Path.Directory as U
+import Data.Text (Text)
+import qualified System.IO.Temp as U
+import RIO
+import Path
+import qualified Data.ByteString as BS
+
+data FSExist m a where
+  DoesFileExist :: Path b File -> FSExist m Bool
+  DoesDirExist  :: Path b Dir  -> FSExist m Bool
+
+makeSem ''FSExist
+
+data FSRead m a where
+  ReadFileBS   :: Path b File -> FSRead m BS.ByteString
+  ReadFileUtf8 :: Path b File -> FSRead m Text
+
+makeSem ''FSRead
+
+data FSWrite m a where
+  WriteFileBS   :: Path b File -> BS.ByteString -> FSWrite m ()
+  WriteFileUtf8 :: Path b File -> Text -> FSWrite m ()
+
+makeSem ''FSWrite
+
+data FSCopy m a where
+  CopyFile :: Path b File -> Path b' File -> FSCopy m ()
+
+makeSem ''FSCopy
+
+data FSTemp m a where
+  CreateTempDirectory :: FSTemp m (Path Abs Dir)
+
+makeSem ''FSTemp
+
+data FSDir m a where
+  CreateDirectory :: Path b Dir -> FSDir m ()
+  RemoveDirectory :: Path b Dir -> FSDir m ()
+
+makeSem ''FSDir
+
+runFSExist :: Member (Embed IO) r => Sem (FSExist ': r) a -> Sem r a
+runFSExist = interpret \case
+  DoesFileExist x -> U.doesFileExist x
+  DoesDirExist x  -> U.doesDirectoryExist  x
+
+runFSRead :: Member (Embed IO) r => Sem (FSRead ': r) a -> Sem r a
+runFSRead = interpret \case
+  ReadFileBS x   -> embed $ BS.readFile (toFilePath x)
+  ReadFileUtf8 x -> RIO.readFileUtf8 (toFilePath x)
+
+runFSWrite :: Member (Embed IO) r => Sem (FSWrite ': r) a -> Sem r a
+runFSWrite = interpret \case
+  WriteFileBS x y -> embed $ BS.writeFile (toFilePath x) y
+  WriteFileUtf8 x y -> RIO.writeFileUtf8 (toFilePath x) y
+
+runFSCopy :: Member (Embed IO) r => Sem (FSCopy ': r) a -> Sem r a
+runFSCopy = interpret \case
+  CopyFile x y -> U.copyFile x y
+
+runFSDir :: Member (Embed IO) r => Sem (FSDir ': r) a -> Sem r a
+runFSDir = interpret \case
+  CreateDirectory x -> U.createDirectoryIfMissing True x
+  RemoveDirectory x -> U.removeDirectoryRecursive x
+
+runFSTemp :: Member (Embed IO) r => Sem (FSTemp ': r) a -> Sem r a
+runFSTemp = interpret \case
+  CreateTempDirectory -> do
+    x <- embed U.getCanonicalTemporaryDirectory
+    embed $ U.createTempDirectory x "" >>= parseAbsDir