Minimal GnuPlot intro
I use gnuplot sufficiently rarely that I can never remember how to drive it from one session to the next. Here is a really minimal 'getting started (again)' guide:
% gnuplot ... gnuplot> set terminal gif gnuplot> set output 'myplot.gif' gnuplot> plot 'myfile.dat' with lines gnuplot> quit
...will take 'myfile.dat' - which contains two columns of numbers for X and Y coordinates - and will plot them with some sort of reasonable axes and put the result out into a '.gif' file called 'myplot.gif'.
Neither the 'man' nor 'info' pages are very friendly (like it would be nice to have some decent examples so I can do the basic stuff without having to relearn the entire package!) and the 'gnuplot --help' thing is useless. The interactive help feature is best:
% gnuplot ... gnuplot> help
gnuplot> help command