Gnuplot scripting set terminal gives me ascii characters

Question

I am trying to run gnuplot script in xubuntu that had worked last months but from today it gives me ascii characters and not the desired png file with plot. I track the problem and seems that is at set terminal command. Any idea?

#!/usr/bin/gnuplot 

reset 
set terminal png size 1024,768 

set xlabel "Time" 
set ylabel "Position" 
set title "Title1" 
set key reverse Left outside 
set grid 
set style data lines 

plot "file.txt" using 1:2 title "North", \ 
     "" using 1:3 title "East", \ 
     "" using 1:4 title "Up" #

Answer 1

Finally found a solution,

worked only gif file so i sudo apt-get purge gnuplot* and reinstall sudo apt-get install libgd2-noxpm-dev then reinstall sudo apt-get install gnuplot-x11 and everything works!!!!!