sorta-OT graph snmp values

[surfer at mauigateway.com (Scott Weeks)]

First, please don't respond with "use mrtg, rrdtool, cricket, etc, etc."  Silly 'layer 8' reasons are keeping me from being able to utilize these tools at this time.  

I have a need to graph SNMP values created by using a simple shell script on a Solaris box.  I have output like this:

02-20-2009_08:00         39      19      20      18
                         23      19      18      18
........ <snip 9 rows of data w/o the date> ........
                         26      20      20      17
02-20-2009_09:00         23      20      22      18


I want to find a program that will allow me to graph the dates on the x-axis and the values on the y-axis, but I need it to be programmable such that I can run it from cron and send the graph to a directory as a jpeg, gif or png file.  I tried using gnuplot, but I can't seem to make it work on outputting only to a file.  Even using "set output graph.png".  Can someone push me in the right direction?

I'm not sure, but this should probably be discussed off-list...

Thanks,
scott