Create an executable file that copies stdin to stdout, or else a script that does so through the invocation of an interpreter at the command line.

start_up = proc ()
    pi: stream := stream$primary_input()
    po: stream := stream$primary_output()
 
    while true do
         stream$putc(po, stream$getc(pi))
    end except when end_of_file:
         return
    end
end start_up