how to extract the first and the last x lines of a big file

If you are debugging big txt files, i.e. 6G+, a good start is to check what is at the top and at the end of it.

export file=/Users/racoonlab/Downloads/engine.out; head -n 1000 $file >/tmp/extract; echo ... skipping ... >> /tmp/extract; tail -n 1000 $file >> /tmp/extract