Capture finite number of samples


Hi everybody.

I’m working in gnu-radio and I must to save a finite number of samples,
to do that I’m using a file sink block, and it do it fine, but I don’t
understand why the samples are saving at the end of the signal, knowing
that I’m using a trigger time to take the samples.
Is there any documentation about it?, I need to understand how works the
file sink block, how it save the samples when I have a complex signal.

Thanks for your help.