Gnuplot

I use gnuplot from time to time. I don't know it well enough to do anything fancy, but I keep it in my toolbox. Most of the time I just want to plot some points from a data file.

[gnuplot documentation]

First I do is alias "gnuplot" to "gnuplot -persist":

alias gnuplot='gnuplot -persist'

You can also put this in your gnuplot script when you set the terminal:

set terminal x11 persist

This will tell gnuplot to keep an image displayed on the screen. By default gnuplot will close a display window as soon as it finishes drawing.

I don't run an ntp daemon.Instead, I just sync my clock once a day using ntpdate. The ntpdate log file looks like this:

28 Jul 04:02:41 ntpdate[4781]: step time server 192.43.244.18 offset 13.828862 sec
29 Jul 04:02:45 ntpdate[19059]: step time server 192.43.244.18 offset 13.838561 sec
30 Jul 04:03:36 ntpdate[17510]: step time server 192.43.244.18 offset 13.844762 sec

I save the output from ntpdate to a log file. I can plot the daily clock drift using this gnuplot script:

set terminal x11 persist
set data style errorlines
set title "Daily clock offset\nnegative means clock runs fast"
set xlabel "Date"
set xdata time
set timefmt "%d %b %H:%M:%S"
set format x "%d/%m"
set ylabel "Required offset (negative minutes fast)"
set yrange [ -1.0 : 30.0]
set grid
plot "ntpdate.log" using 1:10

other examples

For using with `cdck`

#!/usr/bin/env gnuplot
set terminal x11 persist
set data style errorlines
set grid
set xlabel 'Sectors (2Kb/sec)'
set ylabel 'Reading time (usec)'
#set logscale y

plot 'cdck-plot.dat' with lines

old style, depricated:

set terminal png 
#gif small size 640,480
set title "Daily clock offset\nnegative means clock runs fast"
set data style fsteps
set xlabel "Date"
set timefmt "%d/%m/%y\t%H%M"
set yrange [ -4.6 : -4.8]
set xdata time
set xrange [ "25/06/00":"29/08/00" ]
set ylabel "Required offset (negative minutes fast)"
set format x "%d/%m"
#\n%H:%M"
set grid
set key left
plot "data.dat" using 1:10
reset