make a full width longtable in latex/PDF

[seven1240]

Describe your proposed improvement and the problem it solves.

I'd like to make a \textwidth longtable in latex/PDF, but I haven't find a way to make it, is it possible to do that with an option or I can add some renewcommand in preamble to do that? the longtable doc said it's possible.

produces a full width table, to get a similar effect with longtable specify
\setlength\LTleft{0pt}
\setlength\LTright{0pt}
\begin{longtable}{@{\extracolsep{...}}...}

Describe alternatives you've considered.

Thanks.