I hadn't used gnuplot, but when my UPS was dying, I decided I needed a realtime graph of it recharging/discharging to see what was going on. I called the apcup

I hadn't used gnuplot, but when my UPS was dying, I decided I needed a realtime graph of it recharging/discharging to see what was going on. I called the apcupsd api from the command line and output some stats to a file that I'd formatted into columns using awk/grep, I then found that I could configure gnuplot to draw a graph from this file, and then update itself automatically as the file changed. All in all, it took me 10 minutes to put together having not used gnuplot before and did exactly what I needed. I could watch the graph update every few seconds/minutes and keep an eye on what was happening, and because I had written the data to a file first, I could always go back and re-plot it later if I had found anything interesting to re-plot for. End result; UPS is dead, get a new one :D