diff --git a/src/GF/Shell.hs b/src/GF/Shell.hs
index ac5a5d660..8ae01017c 100644
--- a/src/GF/Shell.hs
+++ b/src/GF/Shell.hs
@@ -5,9 +5,9 @@
 -- Stability   : (stable)
 -- Portability : (portable)
 --
--- > CVS $Date: 2005/06/20 16:14:19 $ 
+-- > CVS $Date: 2005/07/01 08:16:32 $ 
 -- > CVS $Author: aarne $
--- > CVS $Revision: 1.41 $
+-- > CVS $Revision: 1.42 $
 --
 -- GF shell command interpreter.
 -----------------------------------------------------------------------------
@@ -208,6 +208,8 @@ execC co@(comm, opts0) sa@((st,(h,_)),a) = checkOptions st co >> case comm of
         _ -> Nothing
     returnArg (ATrms $ generateTrees opts gro mt) sa
 
+  CShowTreeGraph | oElem emitCode opts -> do -- -o
+    returnArg (AString $ visualizeTrees opts $ strees $ s2t a) sa
   CShowTreeGraph  -> do
     let g0 = writeFile "grphtmp.dot" $ visualizeTrees opts $ strees $ s2t a
         g1 = system "dot -Tps grphtmp.dot >grphtmp.ps" 
diff --git a/src/GF/Shell/HelpFile.hs b/src/GF/Shell/HelpFile.hs
index 6a95ff7bf..6a1b55d33 100644
--- a/src/GF/Shell/HelpFile.hs
+++ b/src/GF/Shell/HelpFile.hs
@@ -5,9 +5,9 @@
 -- Stability   : (stable)
 -- Portability : (portable)
 --
--- > CVS $Date: 2005/06/20 16:14:19 $
+-- > CVS $Date: 2005/07/01 08:16:32 $
 -- > CVS $Author: aarne $
--- > CVS $Revision: 1.6 $
+-- > CVS $Revision: 1.7 $
 --
 -- Help on shell commands. Generated from HelpFile by 'make help'.
 -- PLEASE DON'T EDIT THIS FILE.
@@ -317,6 +317,11 @@ txtHelpFile =
   "\n      -c           show categories only (no functions)" ++
   "\n      -f           show functions only (no categories)" ++
   "\n      -g           show as graph (sharing uses of the same function)" ++
+  "\n      -o           just generate the .dot file" ++
+  "\n  examples:" ++
+  "\n    p \"hello world\" | vt -o | wf my.dot ;; ! open -a GraphViz my.dot" ++
+  "\n    -- This writes the parse tree into my.dot and opens the .dot file" ++
+  "\n    -- with another application without generating .ps." ++
   "\n" ++
   "\n-- subshells" ++
   "\n" ++
diff --git a/src/GF/Shell/ShellCommands.hs b/src/GF/Shell/ShellCommands.hs
index e2b809b21..9d6718faf 100644
--- a/src/GF/Shell/ShellCommands.hs
+++ b/src/GF/Shell/ShellCommands.hs
@@ -5,9 +5,9 @@
 -- Stability   : (stable)
 -- Portability : (portable)
 --
--- > CVS $Date: 2005/06/20 16:14:20 $ 
+-- > CVS $Date: 2005/07/01 08:16:32 $ 
 -- > CVS $Author: aarne $
--- > CVS $Revision: 1.38 $
+-- > CVS $Revision: 1.39 $
 --
 -- The datatype of shell commands and the list of their options.
 -----------------------------------------------------------------------------
@@ -191,7 +191,7 @@ optionsOfCommand co = case co of
   CSpeakAloud -> flags "language"
   CPutString -> both "utf8" "filter length"
   CShowTerm -> flags "printer"
-  CShowTreeGraph -> opts "c f g"
+  CShowTreeGraph -> opts "c f g o"
   CSystemCommand _ -> none
 
   CPrintGrammar -> both "utf8" "printer lang"
diff --git a/src/HelpFile b/src/HelpFile
index dcd246858..03a1c1be5 100644
--- a/src/HelpFile
+++ b/src/HelpFile
@@ -288,6 +288,11 @@ vt, visualize_tree: vt Tree
       -c           show categories only (no functions)
       -f           show functions only (no categories)
       -g           show as graph (sharing uses of the same function)
+      -o           just generate the .dot file
+  examples:
+    p "hello world" | vt -o | wf my.dot ;; ! open -a GraphViz my.dot
+    -- This writes the parse tree into my.dot and opens the .dot file
+    -- with another application without generating .ps.
 
 -- subshells