I came across a long list of useful UNIX commands put together by Seth Brown. You'll appreciate many and remember a few.
By Matthew Malinowski, 2012-12-03
Check this out: http://www.drbunsen.org/explorations-in-unix.html. Seth Brown with some seriously useful Unix commands to inspect your data.
A simple one that you've got some variation on already, probably:
That returns the first five and last five lines of datafile.
Or, for inspecting multiple files:
This prints the first three lines of everything starting with file, but prints the name of each file before the lines. Awesome.