XML in Linux and Unix

XML is crucial in Linux and Unix systems, offering a versatile and standardized approach to data representation and exchange. It’s like a flexible and standard way to handle data. 

In this article, we’ll talk about what’s XML, why XML matters in Linux and Unix operating systems and how it affects things like configuration files, processing data, and making different systems work together. Let’s explore why XML is a big deal in the world of Linux and Unix.

The Basics of XML

XML has become one of the most important tools for storing and transporting data. It doesn’t depend on any software or hardware, hence its growing popularity for numerous platforms, including Linux and Unix.

XML is basically an Extensible Markup Language. Being a markup language, it’s similar to HTML, but it was made to be self-descriptive.

What is XML?

XML is a markup language and a file format suitable for storing and transferring data. It comes with a bunch of rules to encode documents in a format that both people and machines can read, making data selection a breeze.

XML comes with more benefits. It’s not a computer language; hence, its profile is understandable, even for beginners. It’s similar to code to HTML, maybe even easier. It’s portable and compatible with Java, but also extendable.

XML Syntax and Structure

XML consists of more documents. Here are the most important ones:

• Documents. Similar to HTML, XML uses <xml></xml> tags.
• Declarations. Files have a declaration in the beginning to define the XML version.
• Elements. Extra tags in a document are known as elements.
• Attributes. XML files have descriptions of XML elements.
• Content. All the data in XML files is referred to as the content.
• Schema. Schema covers boundaries to the structure.
• Parser. This is the software that evaluates files by checking syntax.

How is XML useful in Linux and Unix

XML is widely used for more platforms, but it comes with certain advantages in Linux and Unix.

Configuration Files

Many configuration files in Linux and Unix rely on the XML format. Fortunately, the format has been fully integrated into Linux and Unix due to its open source profile.

Processing documents in Linux and Unix is fairly simple and can be done in more ways, such as using XMLStarlet, the command line utility xmllint (offered by the libxml2 library), the xml.etree.ElementTree module in Python, the XML::LibXML module in Perl or Saxon-HE, an open source processor.

While not recommended to beginners, the XML configuration files in Linux and Unix can also be modified.

System Administration and Automation

XML is text-based yet understandable by humans. Regarding system administration, XML files in Linux and Unix can be edited for more efficiency, but this isn’t suitable for newbies.

Automation is a different kettle of fish. Programmers use XML to automate processes, such as subscription services. This is probably the most obvious example, as XML has been used to develop the popular RSS.

Basically, it’s one thing to check a page on a regular basis to see if anything has changed and a different thing to use XML and subscribe to it. The XML has been used to write a script that covers this task. The RSS took years to develop, but it’s the perfect example of automation using XML.

Tools and Utilities for XML in Linux/Unix

Given the full integration of XML in Linux and Unix, there are clearly quite a few tools to help process such files.

Editors and Validators

Originally designed as a text editor, Vim can also be used to edit XML files. Gedit is also suitable, especially since it’s also built to format XML files. Emacs works too, but it requires the nXML mode to edit XML documents.

Other useful editors and tools include:

• XSD / WSDL Visualizer
• EditiX
• Code Browser
• Kate
• Eclipse PHP

The xmllint command belongs to the xmllib2 package and is mainly used as a validator.

Those who use command prompts may also view XML files with the XMLStarlet command.

Command-Line Tools

Use sudo apt install xmlstarlet for Linux Mint, Debian or Ubuntu to install XMLStarlet. Run xmlstarlet –help, and you’ll see a list of all available commands.

The xmllint command is just as popular. Its general syntax is xmllint [options] xml_file_1 xml_file_2 and so on. You can use it for parsing and quick validation, prettifying XML, removing blank spaces, clearing DTD from output or validating XML, among others.

A different xmllint version is also available for Linux.

Programming and Scripting

Parsing is extremely common in programming and scripting and implies extracting specific data from XML files. Data can also be converted into different formats or validated, not to mention the option to search for something in particular.

XMLStarlet is rich in features and allows parsing XML files in no time. The xml.etree.ElementTree module in Python is also highly efficient at parsing, manipulating and using XML files.

Those who use Perl can rely on the XML::LibXML module, renowned for its flexible API.

Another approach includes Saxon-HE, which parses XML files through XQuery and XPath expressions. It’s a third-party piece of software, but XML isn’t software-dependent, so they’re compatible. It can be downloaded from its official website.

Even at large scale with complex XML files and data there are tools available like Flexter Converter that are very useful to handle big volumes of data very easily.

Final thoughts

XML stands as a fundamental asset within the Linux and Unix environments, providing a flexible and standardized method for managing data. Its role encompasses a wide range of functions, from encoding configuration files to facilitating system interoperability and automation. 

Moreover, XML’s user-friendly nature and widespread compatibility make it an invaluable tool for both beginners and seasoned professionals in the realm of system administration and programming.