diff --git a/dwtt b/dwtt
index ce63424..cd583b5 100755
--- a/dwtt
+++ b/dwtt
@@ -54,40 +54,49 @@ def main(argv):
             break
         cmd = Command(cmdline)
         res = processCommand(cmd, ds)
-        if type(res).__name__ == 'bool':
-            if not res:
-                break
-        elif type(res).__name__ == 'str':
-            # todo: move to GUI
-            print "Error:", res
-        else:
-            print "Unknown return type '%s'" % type(res).__name__
+        if not res.keepwindow:
+            break
+
+class Result:
+    def __init__(self):
+        self.keepwindow = False
+        self.error = ''
+        self.message = ''
+        self.formatted = ''
 
 def processStart(cmd, store):
+    res = Result()
     processOut(cmd, store)
     task = store.getTaskByShortName(cmd.argstr)
     if task is None:
         parent = store.getParentTaskByShortName(cmd.argstr)
         if parent is None:
-            return 'Could not find task "%s"' % \
+            res.error = 'Could not find task "%s"' % \
                     (':'.join(cmd.argstr.split(':')[:-1]))
+            res.keepwindow = True
+            return res
         taskid = store.createTask(cmd.argstr.split(':')[-1], '', parent.taskid)
     else:
         taskid = task.taskid
     store.updateCurrentTask(TaskRef(taskid, cmd.time))
-    return False
+    return res
 
 def processOut(cmd, store):
+    res = Result()
     ct = store.getCurrentTask()
-    if ct is not None:
-        seconds = (cmd.time - ct.time).seconds
-        if seconds > 0:
-            store.addTime(cmd.time.strftime('%Y-%m-%d'), ct.taskid, seconds)
-        store.clearCurrentTask()
-        return False
-    return 'No current task defined'
+    if ct is None:
+        res.error = 'No current task defined'
+        res.keepwindow = True
+        return res
+    seconds = (cmd.time - ct.time).seconds
+    if seconds > 0:
+        store.addTime(cmd.time.strftime('%Y-%m-%d'), ct.taskid, seconds)
+    store.clearCurrentTask()
+    return res
 
 def processTask(cmd, store):
+    res = Result()
+    res.keepwindow = True
     parts = cmd.argstr.split(',', 1)
     fullname = parts[0].strip()
     longname = '' if len(parts) < 2 else parts[1].strip()
@@ -96,17 +105,22 @@ def processTask(cmd, store):
     if task is not None:
         # the task already exists, update it
         store.updateTask(task.taskid, nameparts[-1], longname)
-        return False
+        res.message = 'Task "%s" updated' % fullname
+        return res
     if len(nameparts) > 1:
         parenttask = store.getParentTaskByShortName(fullname)
         if parenttask is None:
-            return 'Parent task not found'
+            res.error = 'Parent task of "%s" not found' % fullname
+            return res
         store.createTask(nameparts[-1].strip(), longname, parenttask.taskid)
     else:
         store.createTask(nameparts[-1].strip(), longname, None)
-    return False
+    res.message = 'Task "%s" created' % fullname
+    return res
 
 def processStatus(cmd, store):
+    res = Result()
+    res.keepwindow = True
     now = datetime.now()
     monday = now - timedelta(now.weekday())
     sunday = monday + timedelta(6)
@@ -119,7 +133,7 @@ def processStatus(cmd, store):
             print store.getTaskPath(task) + ':'
         hours = round(float(ent.seconds) / (60 * 60), 1)
         print '  %s: %0.1f' % (ent.date, hours)
-    return False
+    return res
 
 COMMAND_HANDLERS = {
         'start'     : processStart,
@@ -132,8 +146,10 @@ COMMAND_HANDLERS = {
 def processCommand(cmd, store):
     if cmd.command in COMMAND_HANDLERS:
         return COMMAND_HANDLERS[cmd.command](cmd, store)
-    # todo: error on command not found
-    return False
+    res = Result()
+    res.error = 'Unknown command: %s' % cmd.command
+    res.keepwindow = True
+    return res
 
 if __name__ == "__main__":
     main(sys.argv)