command-line web-compatible graph / imag

I am looking for a free, command-line utility that creates images using data from standard input or from a file. I want to create a graph, including labels, from data generated by another script and include that graph in a webpage. If there’s a tool to do this that comes standard with *nix, let me know what it is, please. If there isn’t point me in the right direction. (I already looked into graph, but it won’t do labels, that I can see.)