Creating Web Plots on Demand

Mr. Pruett tells us how his company creates on-the-fly plots of database information for web display.
Cleaning Up the GIF Files

One minor issue remains. We create a new GIF file each time our Perl program is run, so we must get rid of them when they're no longer needed.

In my case, each night I simply run a script under crontab that deletes any GIF files created during the day. Since most of our applications are run during the daytime hours, the chances of deleting a GIF file I still need are very small.

This scheme might not be acceptable in every situation, so you may need to devise a different way to clean up the GIF files that collect on your web server. [The find command will fit this purpose admirably—Ed]

Reviewing the Steps

While I've provided a specific example of on-demand plotting, the techniques used can be applied to any type of data you might want to plot. If you can extract the data to a simple text file, and if the data lends itself to two- or three-dimensional plotting, you can deliver it to the Web. The basic steps are always the same:

  • Build a text file with the data to plot.

  • Build a gnuplot command file.

  • Run gnuplot to build the plot in PPM format.

  • Convert the plot to GIF format using ppmtogif.

  • Build an HTML page with the image tag and send it to the browser.

Tying together tools like gnuplot and NetPBM to quickly build a useful program shows that software doesn't necessarily have to come packaged in the latest object-oriented component, tied together with ActiveX or CORBA. Often, good solid tools, text files and a touch of Perl will more than suffice to do the job.

Resources

Mark Pruett received his M.S. in computer science from Virginia Commonwealth University. Mark is a programmer who writes about programming. He hopes some day to be a writer who writes about how to write program documentation. He can be reached at pruettm@vancpower.com.

______________________

White Paper
Linux Management with Red Hat Satellite: Measuring Business Impact and ROI

Linux has become a key foundation for supporting today's rapidly growing IT environments. Linux is being used to deploy business applications and databases, trading on its reputation as a low-cost operating environment. For many IT organizations, Linux is a mainstay for deploying Web servers and has evolved from handling basic file, print, and utility workloads to running mission-critical applications and databases, physically, virtually, and in the cloud. As Linux grows in importance in terms of value to the business, managing Linux environments to high standards of service quality — availability, security, and performance — becomes an essential requirement for business success.

Learn More

Sponsored by Red Hat

White Paper
Private PaaS for the Agile Enterprise

If you already use virtualized infrastructure, you are well on your way to leveraging the power of the cloud. Virtualization offers the promise of limitless resources, but how do you manage that scalability when your DevOps team doesn’t scale? In today’s hypercompetitive markets, fast results can make a difference between leading the pack vs. obsolescence. Organizations need more benefits from cloud computing than just raw resources. They need agility, flexibility, convenience, ROI, and control.

Stackato private Platform-as-a-Service technology from ActiveState extends your private cloud infrastructure by creating a private PaaS to provide on-demand availability, flexibility, control, and ultimately, faster time-to-market for your enterprise.

Learn More

Sponsored by ActiveState