Bison and $ (dollarsign) token at the end

[Grzegorz_Szostak]

Hello,
I run bison -v "myfile.y" and got output where last two rules I can't
understand:
----------------------------------------
state 15

    $           go to state 16



state 16

    $           go to state 17



state 17

    $default    accept
-----------------------------------------

If parser is in state 15 it needs two $ to accept... huh what $ is for? Is
it some kind of "end of input"?
How can I make yylex (flex++) make returns twice (-1)?
Waiting for reply...

GSZ