[c3RlcGhlbnI_]

Apparently so can gnuplot, however the syntax is really awful.

    awk 'BEGIN{ for(x=-5;x<6.5;x+=0.1){printf("%s\t%f\n", x, sin(x))} }' \
      | gnuplot -p -e "set term dumb size 89,30 aspect 1;plot '<cat'"

Gnuplot really isn't made for that kind of usage, so guff does fill a valuable niche. Though you could also just write a wrapper around gnuplot with an interface that works better for command line usage(this probably already exists).