In Unix, graph is a command-line utility used to draw plots from tabular data.
The graph utility, written by Douglas McIlroy, was present in the first version of Unix, and every later version, for instance: Its output is a sequence of commands for the plot utility, which creates plots using ASCII graphics.
[4] The GNU plotutils package provides a free non-exact reimplementation, available for Linux and many other systems.
In its simplest use, the graph utility takes a textfile containing pairs of numbers, indicating the points of a line plot.
This demo was run on Ubuntu, which makes GNU plotutils available as an optional package; many other Linux distributions and other Unix-like systems do the same.