We have only scratched the surface of the OpenACS templating system. ad_page_contract additionally supports verification routines that allow you to check multiple parameters or to signal errors based on information found in the database. You actually can define your own custom error messages that may appear in the case of trouble. Even outside of ad_page_contract, a .tcl page also can call the universal ad_return_complaint function, which produces error messages in nicely formatted HTML pages.
In addition, the OpenACS templating system has a complete set of form-building routines that allow a programmer to specify an HTML form using Tcl procedures. The contents of the form then can be exported to the .adp page using data sources. Not only does the form builder cut down on the amount of HTML you have to write, but it makes it easy to create a two-stage form submission process, in which users get a chance to preview their work before sending it in.
Finally, OpenACS templates include a number of additional tags, such as <if>, that allow you to include text and images conditionally, depending on the values of other data sources.
While OpenACS is often touted as a remarkable system because of its elaborate data model and advanced applications, I have found the templates to be one of the more compelling parts of OpenACS. The graphic designers with whom I work enjoy the separation between .tcl and .adp pages, and I like that I can check for errors and pass multiple values without having to remember that there is no obvious connection between them at the HTTP level.
While the learning curve for OpenACS can be quite steep, learning how the templates work is both a gratifying and interesting way to start with this system. Given the many application packages that come with OpenACS, there also are numerous examples of the templates right in the code after you download the system.
Reuven M. Lerner is a consultant specializing in web/database applications and open-source software. His book, Core Perl, was published in January 2002 by Prentice Hall. Reuven lives in Modi'in, Israel, with his wife and daughter.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- SUSE LLC's SUSE Manager
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Non-Linux FOSS: Caffeine!
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
- Parsing an RSS News Feed with a Bash Script
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide