Re: Postgres and GnuPlot

Heh. Funny you should ask; I spent a fair amount of time yesterday
doing precisely this.

Here's my gnuplot file:

set terminal png small color picsize 1000 400
set style fill solid 1.0 border
set title "Concurrent listeners"
set xdata time
set xlabel "Time"
set ylabel "Cuncurrent Logged In Listeners"
set format x "%Y/%m/%d\n%H:%M:%S"
set timefmt "%s"
plot "< echo \"select t-7*3600,c from stats_concurrent_listener_count
(extract(epoch from '2004/12/13 20:00'::timestamp)::int,null);\" |
psql -h plur -U greenroom gr-dev -t | sed 's/|//'" using 1:2 with boxes

cat file | gnuplot > image.png works perfectly.

The bitch of it is that I seem to be having a hard time running this
as a cgi. I can't figure out. Not that this question has anything to
do with postgres, but maybe somebody else can tell me where I'm going
wrong? My CGI is:


#!/bin/bash

echo -e "Content-type: image/png\n\n";
echo -e "set terminal png small color picsize 1000 400\nset style
fill solid 1.0 border\nset title \"Concurrent listeners\"\nset xdata
time\nset xlabel \"Time\"\nset ylabel \"Cuncurrent Logged In Listeners
\"\nset format x \"%Y/%m/%d\\\n%H:%M:%S\"\nset timefmt \"%s\"\nplot
\"< echo \\\"select t-7*3600,c from stats_concurrent_listener_count
(extract(epoch from '2004/12/13 20:00'::timestamp)::int,null);\\\" | /
usr/bin/psql -h plur -U greenroom gr-dev -t | sed 's/|//'\" using 1:2
with boxes" | /usr/bin/gnuplot

...and it seems that when printing to stdout, it gives a truncated
version of the file. When redirecting, it does not. Maybe that's not
too surprising, if apache is looking for a null to see when stdout
stops.... but I don't know how to get around that.


On May 9, 2005, at 7:51 AM, Hrishikesh Deshmukh wrote:

> Hi All,
>
> Has anybody tried using gnuplot to plot results from queries; there
> are some suggestions given in PostgreSQL Developer's Handbook but i
> have not any luck so far!
> Any pointers as how to send results from queries straight to a simple
> plotting utility (ex:gnuplot)!
>
> Thanks,
> Hrishi
>
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