Is the U.S. Patent and Trademark Office still operating during the current federal government shutdown? So long as the shutdown does not extend beyond the first few weeks of January 2019, the answer is yes.
According to the USPTO: “the agency has access to prior-year fee collections, which enables the USPTO to continue normal operations for a few weeks. Should the USPTO exhaust these funds before a partial government shutdown comes to an end, the agency would have to shut down at that time, although a small staff would continue to work to accept new applications and maintain IT infrastructure, among other functions.”
IP Spotlight 
Now the question is “What is defined as FEW WEEKS?” Did this begin on Dec 26 of 2018? This office states it will continue to accept incoming applications, but what about outgoing determinations and issuances?
The USPTO has not stated how many weeks is a “few”, but when I’ve spoken with folks in the USPTO they expect that it would stay open through at least early February. Until that time, the USPTO continues to operate as usual. If it does shut down, applicants will be able continue filing online, but applicants should not expect the USPTO to issue any new actions during the shutdown.