I just discovered vnStat, a network traffic monitor for Linux. Here’s a blurb from the website:
vnStat is a network traffic monitor for Linux that keeps a log of daily network traffic for the selected interface(s). vnStat isn’t a packet sniffer. The traffic information is analyzed from the /proc -filesystem, so vnStat can be used without root permissions.
It will tell you how much inbound and outbound bandwidth that your Linux machine is using—hourly, daily, weekly, monthly, yearly. That’s handy.
By inspection, I’ve been able to tell that it runs like so: it installs itself as a cron job that runs every five minutes to update its internal database. Then you can type
vnstat on the command line to give you the stats.
I’d post some sample output, but since I’ve just started running it, there’s nothing to show. I’m glad to have found it, though.