Path: csiph.com!eternal-september.org!feeder.eternal-september.org!reader01.eternal-september.org!.POSTED!not-for-mail
From: Veek M <veek@dont-use-this.com>
Newsgroups: comp.graphics.apps.gnuplot
Subject: How do i pipe data to gnuplot/no-fifo and plot the data on the fly
Date: Sun, 16 Feb 2020 02:18:54 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 26
Message-ID: <r2a8qe$mvp$1@dont-email.me>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Injection-Date: Sun, 16 Feb 2020 02:18:54 -0000 (UTC)
Injection-Info: reader02.eternal-september.org; posting-host="197383e99db4c5a00f53a0e835337b5f"; logging-data="23545"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+PiECNsicr8RL8vCyWug9l"
User-Agent: Pan/0.145 (Duplicitous mercenary valetism; d7e168a git.gnome.org/pan2)
Cancel-Lock: sha1:1EEXFJ2pPvI+fKoitsX7UlVhCz4=
Xref: csiph.com comp.graphics.apps.gnuplot:4289

my output is

42.0 27.8 29.8 43.0 42.0 43.0 
42.0 27.8 29.8 43.0 42.0 43.0

while true; do 
   sensors|egrep -o ' \+[0-9]{2}\.[0-9]+°C '|tr -d ' +°C'|tr -s '\n' ' ';
   echo; sleep 1; 
done|gnuplot -p -e '
  set xrange [0:60]; 
  set yrange [20:80]; 
  while (1) { 
    plot "-" using 1:2, "" using 1:3; pause 1; reread; 
  }'

just blocks. 
while true; do sensors|egrep -o ' \+[0-9]{2}\.[0-9]+°C '|tr -d ' +°C'|tr -
s '\n' ' '; echo; sleep 1; done|gnuplot -p -e 'plot "-" using 1:2, "" 
using 1:3'

So I tried
echo 20 40 60|gnuplot -p -e 'set xrange [0:60]; set yrange [20:80]; plot 
"-" using 1:2, "" using 1:3'
> line 1: warning: Skipping data file with no valid points

why is that?