tail
tail [-n N] [-f] <file>
Risk: Safe
What it does
Shows the last lines of a file: the newest ones in a log.
When to use it
To read what just happened.
Example
$ tail -n 3 orders.logThe 3 newest orders.
$ tail -f orders.logKeep watching for new lines. Ctrl+C stops.
Learn it in: Read files: cat, less, head, tail · Official docs