Helping with piping to gnuplot

[Tony7682]

Hi,

I am a new here. I did read the FAQ. I had a specific question about piping data to GNU Plot as part of a bash script.

What I am doing is the following: cat'ing out the contents of an mgen (http://cs.itd.nrl.navy.mil/work/mgen/) log file, piping that to trpr (http://pf.itd.nrl.navy.mil/protools/trpr.html) (which processes the mgen results into gnuplot-readable format), and then piping that output to gnuplot.

Here is the bash script I am running:


for i in $(seq 1 180)
do
sleep 10
if [ `expr $i % 6` -ne 0 ]; then
# show snapshot
cat $MGLOGFILE | trpr drec real auto X | gnuplot -noraise -persist
if [ -f $PLOTFILE ]; then
rm -vf $PLOTFILE
fi
else
# show cumulative results
cat $MGLOGFILE | trpr drec auto X output $PLOTFILE && gnuplot -noraise -persist $PLOTFILE
fi
done
(I've tried piping tail -f output instead of cat output to trpr, but that would not work for some reason.)

The above seems to be working ok except for one thing: Each call to the cat | trpr | gnuplot line (bolded above) causes a new, separate gnuplot window to open. What I would like is for each successive call to that line to direct its output to the same gnuplot. That way, I don't have a new gnuplot window popping up every 10 seconds.

My workaround right now is to have a wrapper script that periodically closes any gnuplot windows. I'd rather avoid having to do that, though.

Anyone know how to keep continually writing (and rewriting) to one gnuplot window?

[lensman3]

Try the program "tee" just before the gnuplot. "tee" will let you see the pipe.

[Tony7682]

Thank you for the suggestion about the "tee" program. I have never heard of it nor used it before.

Can you elaborate on what you meant by "using it just before gnuplot"?

I've tried this:

cat $MGLOGFILE | trpr drec real auto X | tee | gnuplot -noraise -persistBut the behavior seems the same as it was before. Each successive call to that line causes another new gnuplot window to pop up.

[Arndt]

Thank you for the suggestion about the "tee" program. I have never heard of it nor used it before.

Can you elaborate on what you meant by "using it just before gnuplot"?

I've tried this:

cat $MGLOGFILE | trpr drec real auto X | tee | gnuplot -noraise -persistBut the behavior seems the same as it was before. Each successive call to that line causes another new gnuplot window to pop up.

This is perhaps an approximation of you want to do:


#! /bin/sh

for i in sin cos tan
do
echo $i 1>&2
echo "plot $i(x)"
sleep 3
done | gnuplot -persist


I tried to use a named pipe, but didn't succeed, maybe there is a way. Also, it may be possible to keep terminal output on stdout, and choose another file descriptor to pass the gnuplot commands on.

[Tony7682]

Awesome! That's it! Pipe the entire for loop into gnuplot! Thanks so much!!


for i in $(seq 1 180)
do
sleep 10
cat $MGLOGFILE | trpr drec real auto X
done | gnuplot -persist

[tjoccam]

Hi, I used these hints and they are very useful indeed, but I'm not quite there. I succeeded with an animation using pre-made files. My code snippet is:
( echo "set yrange [-5:5]"
echo "plot sin(x)"
sleep 1
for j in 0 1 2 3 4 ; do
for i in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 ; do
echo "plot \"plot$i\" using 1:2 with linespoints"
sleep 0.15
done
done
) | gnuplot -persist
with some plot files I prepared ahead of time. (Without the plot sin(x) it pauses and then spits out several plots.) What I really want is to pipe in the output of 1 program, which has its own internal pauses, giving me an animation. Embedding plot "-" or plot '-' does not seem to work. What am I missing? TIA, Larry

[Arndt]

Hi, I used these hints and they are very useful indeed, but I'm not quite there. I succeeded with an animation using pre-made files. My code snippet is:
( echo "set yrange [-5:5]"
echo "plot sin(x)"
sleep 1
for j in 0 1 2 3 4 ; do
for i in 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 ; do
echo "plot \"plot$i\" using 1:2 with linespoints"
sleep 0.15
done
done
) | gnuplot -persist
with some plot files I prepared ahead of time. (Without the plot sin(x) it pauses and then spits out several plots.) What I really want is to pipe in the output of 1 program, which has its own internal pauses, giving me an animation. Embedding plot "-" or plot '-' does not seem to work. What am I missing? TIA, Larry

I'm not sure. Pipe I/O is buffered, which may be the reason for the pausing problems. If so, maybe using the program 'expect' to connect the two programs will work better.