The input files don't need a specific filename extension; the file
format and an optional gzip compression will be automatically detected.
Near the beginning of the DESCRIPTION section of wireshark(1) or
-L<http://www.wireshark.org/docs/man-pages/wireshark.1.html>
+L<http://www.wireshark.org/docs/man-pages/wireshark.html>
is a detailed description of the way B<Wireshark> handles this, which is
the same way B<Capinfos> handles this.