%
% check for any directive issued from tray
% or by any other method, primarily run/stop
% or show/hide commands
%
 "tray.txt" ofbin
 dup exists
 {
%
% there is a tray file present
% delete file and execute contents
% allows chained directives like waiting for certain events
%
  dup read
  exch del
  execstr
 }
 {
  pop
 } ifelse