How to automatically replot a graph every few seconds in gnuplot?

Question

I have a data file a.dat that is updated every few seconds. I wish to plot it in gnuplot every few seconds to see the changes

plot "a.dat"

What is the easiest way to do it? Thanks.

Answer 1

Make a script with a loop:

while (1) {
    plot "a.dat"
    pause 1      # waiting time in seconds
}

Execute it with gnuplot script.gp.

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For purposes of code structure and debugging, you might prefer the following alternative:

plot "a.dat"

while (1) {
    replot
    pause 1
}

This has the advantage that you do not have to put a complicated plot command inside the loop and do not suffer from incorrect line numbers for the plot command in error messages (that happen in at least some version of Gnuplot).

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Finally, if your Gnuplot is so old that it does not yet support loops, there is the alternative:

plot "a.dat"

pause 1
reread

With reread making the script interpreter jump to the beginning of the file again.

Answer 2

If gnuplot is called with plot commands in the command line (option -e) instead of a command script file, only the version

gnuplot -e "...plot command(s)...; while (1) { pause 1; replot; }"

worked in my case, the other version

gnuplot -e "...plot command(s)...; pause 1; reread;" 

did not.

On windows 10, I have to kill the gnuplot task in the task manager, because if I close the gnuplot window with the close-window-button, the window opens again after one second latest. Does anybody have an idea of how to handle this in a more comfortable way?