src/Pure/System/getopts.scala

 class Getopts private(usage_text: String, options: Map[Char, (Boolean, String => Unit)])
 {
   def usage(): Nothing =
   {
     Output.writeln(usage_text, stdout = true)
-    sys.exit(1)
+    sys.exit(Process_Result.RC.error)
   }
 
   private def is_option(opt: Char): Boolean = options.isDefinedAt(opt)
   private def is_option0(opt: Char): Boolean = is_option(opt) && !options(opt)._1
   private def is_option1(opt: Char): Boolean = is_option(opt) && options(opt)._1