# Make a tmp file
cpu_data_file=$(mktemp /tmp/cpu_data.XXX);
# Fill the file with stuff
sadf -- -u | awk '/%idle/ {print $3" "$6}' > $cpu_data_file
# Make a pretty graph
echo "set terminal dump;
set title 'CPU usage';
set xdata time;
set timefmt '%s';
set xlabel 'Time';
plot '$cpu_data_file' using 1:2 with lines title 'CPU usage';" | gnuplot
# Remove tmp file
rm -f $cpu_data_file