unix - head AND tail of file

Question

Say you have a txt file, what is the command to view the top 10 lines and bottom 10 lines of file simultaneously?

i.e. if the file is 200 lines long, then view lines

Answer 1

(sed -u 10q; echo ...; tail) < file.txt

Just another variation on the (head;tail) theme, but avoiding the initial buffer fill issue for small files.