Graphical Desktop Korn Shell
The familiar “Hello World” Motif application, shown in Listing 1, is actually written in DtKsh instead of C. Similar to C, we initialize the top-level shell widget, then start building the GUI application. Listing 1 shows a standard Motif message dialog using the familiar XmCreateMessageDialog API. In DtKsh, handles to widgets can be retrieved, widgets can be managed and unmanaged, and callbacks can be created. Afterwards, the program enters into the Xt Intrinsic's main loop via XtMainLoop where it processes X protocol events. In this case, clicking on the OK button would be an event processed by the event loop.
The Motif “Hello World” DtKsh application in Listing 1 can be easily ported to C with a few minor changes, shown in Listing 2. By adding some include files, defining some variables, adding some commas and semi-colons, and sprucing up some arguments, we have a C program. The result is that DtKsh shell scripts make the same API calls as the C Motif application.
AIX provides some extra DtKsh help through a GUI builder. Developers can drag and drop widgets onto a canvas, then add logic code to enable the application to do some work. Like any GUI builder, the code is somewhat verbose; however, it is consistent and portable. AIX is the only version of UNIX that offers this feature.
Developers can create their own new APIs for DtKsh by creating glue-layer libraries. Glue-layer libraries enable DtKsh to be extended with built-ins for functions such as system management and networking. The performance advantage of using built-in functions rather than calling to an external command is that built-ins execute within the process of the shell script. Commands that are called externally must create new resources in the operating system and run as separate processes. DtKsh glue layer libraries pass arguments between a normal UNIX C library and the DtKsh shell, and they return a success or failure status. The following list provides a few rules for creating a glue layer:
Name the function with a b_ prefix.
Function returns a 0 integer for success, between 1 and 255 for failure.
Function should take argc and argv as input.
Link your glue-layer libraries shared.
Listing 3 shows a DtKsh shell script that dynamically loads the “example” shared glue-layer library. Once the glue layer library is loaded and the new built-in APIs are defined, the script can make direct calls with arguments to the new built-in functions. In Listing 3, the example built-in is called with the “Hello World” arguments.
By providing in-line built-in functions, we can run scripts much faster because we are not relying on outside programs running as separate system erocesses. Listing 4 shows the C glue-layer for the example built-in shared library. Following the rules outlined above, we prefix the example function with a b_, and we pass in an argument vector and its size. After the function has done its work, we return 0 for success and a positive integer for failure. DtKsh built-in functions can also act as procedures that pass environment variables in and out through its argument list. See Desktop KornShell Graphical Programming by J. Stephen Pendergrast, Jr. [Addison-Wesley, 1995] for more details on how to pass and retrieve environment variables from built-in procedures.
The Desktop Graphical Korn Shell provides programmers with the standard ksh93 baseline APIs with the addition of the X Window System, Motif and the Common Desktop Environment. Shell programmers can write portable shell scripts, prototype GUI shell scripts and migrate GUI shell scripts to faster running C programs. DtKsh also provides programmers with the ability to extend the shell language with built-in shared libraries so that scripts can benefit from feature-rich libraries, such as those for configuration management.
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.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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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|
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- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Parsing an RSS News Feed with a Bash Script
- Google's SwiftShader Released
- 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