Index: /trunk/ippTasks/diff.pro
===================================================================
--- /trunk/ippTasks/diff.pro	(revision 17714)
+++ /trunk/ippTasks/diff.pro	(revision 17715)
@@ -130,5 +130,9 @@
 
     ## generate output log based on filerule (convert the URI to a PATH)
-    $logfile = `ipp_filename.pl --filerule LOG.EXP --camera $CAMERA --class_id $STACK_ID --basename $outroot`
+    $logfile = `ipp_filename.pl --filerule LOG.EXP --camera $CAMERA --class_id $DIFF_ID --basename $outroot`
+    if ("$logfile" == "") 
+      echo "WARNING: logfile not defined in diff.skycell.run"
+      break
+    end
 
     stdout $logfile