show empty svg if there is no data

diff --git a/www/cgi-bin/template.cgi b/www/cgi-bin/template.cgi
index d863e55..f849a5d 100755 (executable)
--- a/www/cgi-bin/template.cgi
+++ b/www/cgi-bin/template.cgi
@@ -25,7 +25,20 @@ echo $QUERY_STRING | grep -q voltage && voltage=1
 set > /dev/shm/$pn.env
 
 cat $dir/template.sql | sed -e "s/2008050087/$pn/" -e "s/x_axis_angle/x_axis_angle + $offset_x/" -e "s/y_axis_angle/y_axis_angle + $offset_y/" | psql --username=dpavlin -A -F "," -t zc > /dev/shm/$pn.txt
+if [ -s /dev/shm/$pn.txt ] ; then
 cat $dir/template.gnuplot | sed -e "s,axes.txt,/dev/shm/$pn.txt," -e "s,^set terminal.*$,set terminal svg," -e "s,^set output.*$,set output," -e "s,-0.3 : 0.3,-$yrange : $yrange," > /dev/shm/$pn.gnuplot
 gnuplot -e "voltage=$voltage" /dev/shm/$pn.gnuplot
+else
+cat << __SVG__
+<?xml version="1.0" encoding="utf-8"  standalone="no"?>
+<svg 
+ width="600" height="1"
+ viewBox="0 0 600 480"
+ xmlns="http://www.w3.org/2000/svg"
+ xmlns:xlink="http://www.w3.org/1999/xlink"
+>
+</svg>
+__SVG__
+fi
 
 #rm /dev/shm/axes.txt.$$ /dev/shm/axes.gnuplot.$$