diff --git a/Doug/Basic.lean b/Doug/Basic.lean
index 7189115..55de2b5 100644
--- a/Doug/Basic.lean
+++ b/Doug/Basic.lean
@@ -2,6 +2,7 @@ def hello := "world"
 
 structure Config where
   useASCII : Bool := false
+  printAll : Bool := false
   currentPrefix : String := ""
 
 abbrev ConfigIO (α : Type) : Type := ReaderT Config IO α
@@ -20,12 +21,16 @@ def currentConfig : ConfigIO Config :=
 def usage : String :=
   "Usage: doug [--ascii]
 Options:
-\t--ascii\tUse ASCII characters to display the directry structure"
+\t--ascii\tUse ASCII characters to display the directry structure
+\t-a\tShow hidden entries"
 
-def configFromArgs : List String → Option Config
-  | [] => some {}
-  | ["--ascii"] => some {useASCII := true}
-  | _ => none
+def configFromArgs (args : List String) : Option Config :=
+  let parse_arg cfg arg :=
+    match arg with
+    | "--ascii" => some {cfg with useASCII := true}
+    | "-a" => some {cfg with printAll := true}
+    | _ => none
+  args.foldlM parse_arg {}
 
 inductive Entry where
   | file : String → Entry
@@ -65,13 +70,16 @@ def doList [Applicative f] : List α → (α → f Unit) → f Unit
 partial def dirTree (path : System.FilePath) : ConfigIO Unit := do
   match ← toEntry path with
   | none => pure ()
-  | some (.file name) => showFileName name
+  | some (.file name) =>
+    if ((← read).printAll) || !(name.startsWith ".") then
+      showFileName name
   | some (.dir name) =>
-    showDirName name
-    let contents ← path.readDir
-    withReader (·.inDirectory)
-      (doList contents.toList fun d =>
-        dirTree d.path)
+    if ((← read).printAll) || !(name.startsWith ".") then
+      showDirName name
+      let contents ← path.readDir
+      withReader (·.inDirectory)
+        (doList contents.toList fun d =>
+          dirTree d.path)
 
 def main (args : List String) : IO UInt32 := do
   match configFromArgs args with