rrdtool 1.11.0 (The header files)

RRD is the Acronym for Round Robin Database. RRD is a system to store
and display time-series data (i.e. network bandwidth, machine-room
temperature, server load average). It stores the data in a very
compact way that will not expand over time, and it presents useful
graphs by processing the data to enforce a certain data density. It
can be used either via simple wrapper scripts (from shell or Perl) or
via frontends that poll network devices and put a friendly user
interface on it.

https://oss.oetiker.ch/rrdtool/