vnstat

Network traffic statistics

low risk

interactive breakdown — edit the command and press Explain
$ 
What it does

Keeps long-term interface traffic statistics.

Examples
vnstat -dDaily usage · explain & risk-check →
Related
iftop
Open the full explainer →More in Networking

Reference text is hand-written and may be incomplete — check man vnstat for your version. Test destructive commands on a non-production system first.