swi prolog script problem

Hello,

The following script "test.pl" has a strange behavior :

__________________________________________
#! /usr/bin/swipl

:- set_prolog_stack(local,  limit(10**9)).  	
								
:- initialization top.

top :-
     current_prolog_flag(argv,LArgs),
     writeln(LArgs),
     halt.
__________________________________________


When I run "test.pl -x"
the result :
[-x]

When I run "test.pl -b"
I obtain the following error :

Message: error(syntax_error(operator_expected),
                file(/home/dominique/Bureau/Recherche/LEa1/Lea1_work
                /test.pl,1,1,1))
[PROLOG SYSTEM ERROR:  Thread 1
	Undefined predicate: initialization/1


Why ?

Thanks for your ideas.

I use SWI-Prolog (Multi-threaded, 64 bits, Version 7.1.4)
under Ubuntu.


Dominique