gnuplot fails in background.

[<pl...@pi...>]

Hi,

I'm not really sure this is a gnuplot problem , I'm having trouble 
seeing where the problem lies.

I have a cgi responder written in C that works fine when running gnuplot 
directly but if I add "&" to the command sting it fails.

I have both post.cgi and test.gnu in my cgi directory , it is called by 
lighttpd in response to a FORM post method.

within post.c :

system("gnuplot test.gnu" );
OK.
system("gnuplot test.gnu &" );
Fails to produce output but the call returns zero since it apparently 
succeeds in creating the gnuplot process and backgrounding it before 
gnuplot  fails.

It looks like a permissions problem or file path but testing from 
command line it works and not backgrounding the process works for the cgi.

First line in test.gnu fails to create the file:
system("touch /www/apache/htdocs/gnuplot.ran");

Equally , calling gnuplot with the full path of the .gnu file also fails.

Why is gnuplot failing when I detach the process?

TIA.