The purpose of vnstati is to provide image output support for
statistics collected using vnstat(1). However, the image file
format is limited to png. All basic outputs of vnStat are
supported excluding live traffic features. The image can be
outputted either to a file or to standard output.

vnstati is the image output command for vnstat(1). It provides
png image file output from database files created using vnStat.

WWW:	http://humdi.net/vnstat/