ToolTalk, in the Common Desktop Environment (CDE), is a message brokering system that enables applications to communicate with each other without having direct knowledge of one another. Client and server applications can be developed independently, mixed and matched, and upgraded separately through plug-and-play. In addition, the Desktop Service can be called to perform methods on file and buffer objects on behalf of ToolTalk.
Figure 1 shows the ToolTalk Service listening for TtChmod client requests. ToolTalk Service brokers pattern-matched Chmod messages to the registered mock change-mode application server (ttchmodd) that is waiting to handle the incoming messages.
ToolTalk brokers the requests from the client to the server application. The Desktop Service can forward CDE object method invocations to the ToolTalk Service. With the Desktop, both C programs and dtksh scripts can initiate actions that are transmitted to the ToolTalk Service. Consequently, client invocations from the dtaction command line, application manager icons, and file manager icons can be directed through the Desktop Service to ToolTalk application services. Therefore, double clicking on a file icon in the file manager can be plugged into a ToolTalk registered application by first routing through the Desktop action and data-type service.
The key to the ToolTalk message brokering system is its ability to define process-type identifiers with specific operations and arguments. In Listing 1, the process-type (ptype) TtChmod will execute the ToolTalk change-mode daemon application ttchmodd. This occurs when the session operation Chmod with file name and mode arguments are matched from a request. Compiling the ptype definition with the tt_type_comp utility will register services for ToolTalk client applications to call. Consider the ptype as a C header file describing an application programming interface (API) and the compiled suite of ToolTalk Services definitions as a library of methods to call. For the list of installed process-type identifiers, try running tt_type_comp -P at the command line to dump the database to the screen.
The file change-mode application (ttchmod) described in Listing 2 is simply the Motif command widget. In Figure 2, the ttchmodd server application graphically prompts the user for a command, then calls the callback command callCB to execute it; however, for this example, the application just prints the command. The file change-mode application quickly becomes a plug-and-play service when it registers itself with the ToolTalk Service, then listens for messages to be handled by its ToolTalkCB receiver routine.
An application must first locate the ToolTalk session associated with the X display to register itself as a service, as shown in Listing 3. After the application sets its default session to the display session, the application can initiate itself as a ToolTalk process and obtain a ToolTalk file descriptor. When the ttchmodd application gets a handle on the ToolTalk session, then it can register the TtChmod process type and join the session to listen for requests.
ToolTalk sends a message to a registered service; the service listens on its ToolTalk file descriptor for input. When input is observed, the ToolTalkCB routine is triggered, and the message is read and analyzed. (See Listing 4.) The message's operation is checked, then the arguments are read from the message. ToolTalk messages are similar to a reentrant version of an ordinary C program's command-line arguments. The ttchmodd service is no longer needed after it reads the message, so the recipient tells the ToolTalk service to discard the message.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
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.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
- SUSE LLC's SUSE Manager
- My +1 Sword of Productivity
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Non-Linux FOSS: Caffeine!
- Managing Linux Using Puppet
- Doing for User Space What We Did for Kernel Space
- Tech Tip: Really Simple HTTP Server with Python
- Rogue Wave Software's Zend Server
- Parsing an RSS News Feed with a Bash Script
- SuperTuxKart 0.9.2 Released
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