Cross-Platform Network Applications with Mono
Mono is Ximian's open-source implementation of Microsoft's .NET development framework. .NET contains several different technologies: a set of compilers for many different languages (including Microsoft's new language, C#) that generates platform-independent bytecode; a virtual machine known as the Common Language Runtime (CLR) that runs these bytecodes; and a class library full of useful programs for performing actions ranging from file I/O to GUI creation and operation.
The Mono implementation includes a CLR that runs on Linux, BSD-based systems (including Mac OS X) and Windows, plus compilers for C# and Basic. Mono is a work-in-progress, and many parts of the .NET class library have yet to be implemented, specifically the Windows.Forms group that contains classes for working with the Windows GUI. However, the Mono developers have released bindings for the GTK user-interface toolkit, so cross-platform graphical applications can be constructed even without 100% .NET compatibility. This article describes how to use C#, Mono and Linux to write a useful program, MonoBlog, that can run on any system that runs Mono and GTK. Some familiarity with Glade and C# is assumed, but only at a basic level. Helpful tutorials can be found in the on-line Resources section.
The Mono Web site has instructions for installing the system on Linux, Mac OS X and Windows platforms (see Resources). You also need two additional C# libraries, GTK# and XmlRpcCS. The systems that MonoBlog runs on require the base GTK libraries, which are available on most Linux systems. They probably need to be installed on Windows and Mac OS X systems, however; packages can be found on the GTK Web site (see Resources). Instructions for installing these libraries can be found on their respective Web pages.
MonoBlog is a Weblog editor that can add new posts to a Weblog and edit old ones, as well as provide a way for a user to change configuration settings. Most Weblog systems implement a common base of functionality known as the MetaWeblog API. MonoBlog uses this to communicate with a variety of different Weblog programs, rather than write a separate back end for Movable Type, LiveJournal or Radio Userland systems. The complete C# code for this example is available on the Linux Journal FTP site (see Resources).
Figures 1 and 2 show the user interface of MonoBlog, created using Glade on Linux. The main window in Figure 1 has text controls for entering Weblog titles and the content, plus a series of buttons for updating the Weblog, clearing the forms and quitting the program. The expanse of white on the left-hand side is a GTKTreeView control, which displays a list of older posts the user can click on in order to update. The window shown in Figure 2 is a simple preferences panel where users enter the information that allows MonoBlog to communicate with their Weblogs.
One of GTK's useful features is libglade, a library that allows us to construct a program's GUI by reading in the XML files created by Glade, specifying the layout of the widgets in the code itself. The GTK# binding includes this functionality, so building the GUI is quite easy. At the start of MonoBlog, we import the GTK and Glade namespaces with the using statement. Then, in the constructor, we have:
Application.Init(); Glade.XML gxml = new Glade.XML("monoblog.glade", null, null); gxml.Autoconnect(this); Application.Run();
The calls to the Application class are required in all GTK programs. Application.Init() performs GTK initialization, and Application.Run() passes control of the program to the GTK main loop, which watches for events and reports signals back when they occur. The standard Glade.XML constructor takes three arguments: a string containing the filename of the Glade file, a string that tells the object the node in the Glade tree where it should start building the interface and, finally, a string that can be used to specify a translation domain for the Glade file in question.
MonoBlog needs to have access to all the nodes in the XML file, both the main window and the preferences panel. No translation is required, so the second and third arguments are null. The Autoconnect() method binds the object given as an argument with the signal handlers and objects defined in the Glade file, allowing that object to respond to events and manipulate widgets. As MonoBlog is a small program, I have contained all the signal handling within the main class. In larger, more complex systems, it might be advisable to separate signal handling out into another class.
To access the widgets, a special declaration is required. The widget must be declared as an instance variable, using a custom attribute:
[Glade.Widget] GTKWidgetType widgetname;
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.
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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