Plotting data with gnuplot from stdin

Question

I have simple python script (smazat.py) that generate some data

for i in range(50):
    print i, i-20

I can make images in windows command line with following command

smazat.py | gnuplot -e "set term png;p '-'" > smazat.png

however when use gnuplot script with the same commands like this

smazat.py | gnuplot smazat.gp > smazat.png

it does not work. What's happening?

Answer 1

If you are on a Unix system, you can use

plot `< cat -`

to achieve this (see pipe plot data to gnuplot script).

On Windows, and since you're using python anyway, you can write a small cat.py python script which passes stdin to stdout:

Script cat.py

from __future__ import print_function
import sys
for line in sys.stdin:
    print(line, file=sys.stdout, end='')

Plot file plot.gp

set term png
plot '< python cat.py'

And then call this with

python smazat.py | gnuplot plot.gp > smazat.png