bin/psql -F ' ' -Atc 'select aid,count(aid) from pgbench_history group by aid order by aid;' >result.dat
gnuplot << EOF
  set size 0.8, 0.8
  set xl "aid"
  set yl "access frequency"
  plot 'result.dat' with linespoints
  set terminal png
  set out "graph.png"
  replot
EOF