Add Chmod module

src/Streamly/Coreutils/Chmod.hs

@@ -0,0 +1,69 @@
+-- |
+-- Module      : Streamly.Coreutils.Chmod
+-- Copyright   : (c) 2022 Composewell Technologies
+-- License     : BSD-3-Clause
+-- Maintainer  : [email protected]
+-- Stability   : experimental
+-- Portability : GHC
+--
+-- change file mode bits.
+
+module Streamly.Coreutils.Chmod
+    (  chmod
+    )
+where
+
+import Data.Bits ((.|.), Bits ((.&.), complement))
+import Data.Default.Class (Default(..))
+
+import qualified System.Posix as Posix
+
+data UserType = Owner | Group | Others deriving (Eq, Ord, Read, Show)
+
+data Permissions = Permissions
+  { readable :: Bool
+  , writable :: Bool
+  , executable :: Bool
+  } deriving (Eq, Ord, Read, Show)
+
+instance Default Permissions where
+    def = Permissions
+        { readable = False
+        , writable = False
+        , executable = False
+        }
+
+modifyBit :: Bool -> Posix.FileMode -> Posix.FileMode -> Posix.FileMode
+modifyBit False b m = m .&. complement b
+modifyBit True  b m = m .|. b
+
+chmod :: UserType -> Permissions -> FilePath -> IO ()
+chmod utype (Permissions r w e) path = do
+    case utype of
+        Owner -> do
+            stat <- Posix.getFileStatus path
+            Posix.setFileMode
+                path
+                ( modifyBit e Posix.ownerExecuteMode
+                . modifyBit w Posix.ownerWriteMode
+                . modifyBit r Posix.ownerReadMode
+                . Posix.fileMode $ stat
+                )
+        Group ->  do
+            stat <- Posix.getFileStatus path
+            Posix.setFileMode
+                path
+                ( modifyBit e Posix.groupExecuteMode
+                . modifyBit w Posix.groupWriteMode
+                . modifyBit r Posix.groupReadMode
+                . Posix.fileMode $ stat
+                )
+        Others -> do
+            stat <- Posix.getFileStatus path
+            Posix.setFileMode
+                path
+                ( modifyBit e Posix.otherExecuteMode
+                . modifyBit w Posix.otherWriteMode
+                . modifyBit r Posix.otherReadMode
+                . Posix.fileMode $ stat
+                )

streamly-coreutils.cabal

@@ -108,6 +108,7 @@ library
   hs-source-dirs:      src
   exposed-modules:
       Streamly.Coreutils
+    , Streamly.Coreutils.Chmod
     , Streamly.Coreutils.Common
     , Streamly.Coreutils.Cp
     , Streamly.Coreutils.Directory