src/Pure/System/isabelle_system.scala

--- a/src/Pure/System/isabelle_system.scala	Sat Dec 07 12:52:31 2013 +0100
+++ b/src/Pure/System/isabelle_system.scala	Sat Dec 07 13:10:56 2013 +0100
@@ -419,6 +419,12 @@
     }
   }
 
+  def open(arg: String): Unit =
+    bash("exec \"$ISABELLE_OPEN\" '" + arg + "' >/dev/null 2>/dev/null &")
+
+  def pdf_viewer(arg: Path): Unit =
+    bash("exec \"$PDF_VIEWER\" '" + standard_path(arg) + "' >/dev/null 2>/dev/null &")
+
 
 
   /** Isabelle resources **/