XML Formatting Made Easy (with examples)
XML documents are widely used for storing and transferring data. However, working with raw XML can be challenging due to its lack of proper formatting and indentation. Luckily, xmlstar provides a powerful command, xml format, that makes formatting XML documents a breeze. In this article, we will explore several use cases of the xml format command and learn how it can simplify XML document formatting.
Use Case 1: Indentation with Tabs
xml format --indent-tab path/to/input.xml|URI > path/to/output.xml
Motivation: When working with XML documents, maintaining proper indentation greatly improves readability and makes it easier to navigate through the structure of the document. By using the --indent-tab option, the xml format command indents the XML document using tab characters.
Explanation:
--indent-tab: This option tells thexml formatcommand to use tab characters for indentation. By default, the command uses spaces for indentation.path/to/input.xml|URI: The path or URI of the input XML document.> path/to/output.xml: Redirects the formatted XML to the specified output file.
Example Output:
<?xml version="1.0"?>
<root>
<element1 attribute="value1">
<child1>data1</child1>
<child2>data2</child2>
</element1>
<element2 attribute="value2">data3</element2>
</root>
Use Case 2: Indentation with Spaces for HTML Documents
xml format --html --indent-spaces 4 path/to/input.html|URI > path/to/output.html
Motivation: While both XML and HTML are markup languages, the formatting conventions for HTML documents are slightly different. HTML documents are traditionally indented using spaces instead of tabs, and this helps maintain consistency with HTML development practices. The xml format command allows us to format HTML documents using spaces for indentation.
Explanation:
--html: This option informs thexml formatcommand that the input document is an HTML document. By default, it assumes XML documents.--indent-spaces 4: This option specifies that the document should be indented using 4 spaces for each level of nesting.path/to/input.html|URI: The path or URI of the input HTML document.> path/to/output.html: Redirects the formatted HTML to the specified output file.
Example Output:
<!DOCTYPE html>
<html>
<head>
<title>Example</title>
</head>
<body>
<h1>Welcome</h1>
<p>This is a sample HTML document.</p>
</body>
</html>
Use Case 3: Recovering Parsable Parts of a Malformed XML Document
xml format --recover --noindent path/to/malformed.xml|URI > path/to/recovered.xml
Motivation: XML documents can sometimes be malformed due to syntax errors, missing elements, or incorrect nesting. Parsing such malformed documents can be a challenge as most XML parsers require well-formed input. The xml format command provides a convenient way to recover parsable parts of a malformed XML document while ignoring the malformed sections.
Explanation:
--recover: This option instructs thexml formatcommand to attempt recovering parsable parts from a malformed XML document.--noindent: This option disables the indentation, making the recovered XML easier to analyze.path/to/malformed.xml|URI: The path or URI of the malformed XML document.> path/to/recovered.xml: Saves the recovered XML to the specified output file.
Example Output:
<root>
<element1 attribute="value1">
<child1>data1</child1>
<child2>data2</child2>
</element1>
<element2 attribute="value2">data3</element2>
</root>
Use Case 4: Removing the DOCTYPE Declaration
cat path\to\input.xml | xml format --dropdtd > path/to/output.xml
Motivation: A DOCTYPE declaration is used in XML documents to define the structure and rules associated with the document. In some cases, it might be necessary to remove the DOCTYPE declaration, especially when the document is being modified or used in a context where the declaration is not needed. The xml format command provides the --dropdtd option to exclude the DOCTYPE declaration from the output.
Explanation:
--dropdtd: This option instructs thexml formatcommand to remove the DOCTYPE declaration from the input XML document.cat path/to/input.xml: Utilizes thecatcommand to read the input XML document from standard input.> path/to/output.xml: Redirects the XML document without the DOCTYPE declaration to the specified output file.
Example Output:
<?xml version="1.0"?>
<root>
<element1 attribute="value1">
<child1>data1</child1>
<child2>data2</child2>
</element1>
<element2 attribute="value2">data3</element2>
</root>
Use Case 5: Omitting the XML Declaration
xml format --omit-decl path\to\input.xml|URI > path/to/output.xml
Motivation: The XML declaration, which begins with <?xml ?>, specifies the version and character encoding of an XML document. In some cases, it may be necessary to remove the XML declaration to conform to certain requirements or when merging XML documents. The xml format command provides the --omit-decl option to exclude the XML declaration from the output.
Explanation:
--omit-decl: This option tells thexml formatcommand to omit the XML declaration from the input XML document.path\to\input.xml|URI: The path or URI of the input XML document.> path/to/output.xml: Redirects the XML document without the XML declaration to the specified output file.
Example Output:
<root>
<element1 attribute="value1">
<child1>data1</child1>
<child2>data2</child2>
</element1>
<element2 attribute="value2">data3</element2>
</root>
Use Case 6: Displaying Help for the format subcommand
xml format --help
Motivation: The xml format command provides various options and parameters that can be customized based on specific requirements. In case you need a quick reference for the available options and their usage, you can use the --help option to display the help information.
Example Output:
Usage: xml format [OPTION]... [FILE|URI...]
Format an XML document.
Options:
--help Display this help message and exit
--version Output version information and exit
--debug Enable debug output
--indent-spaces COUNT Number of spaces per indentation level (default: 2)
--indent-tab Use tabs for indentation instead of spaces
--html Format the input as HTML
--recover Attempt to recover parsable parts from malformed documents
--noindent Do not perform any indentation (default is to indent)
--dropdtd Drop the DOCTYPE declaration
--omit-decl Omit the XML declaration
Conclusion
The xml format command provided by xmlstar is a valuable tool for formatting XML and HTML documents. Whether you need to indent XML using tabs, recover parsable parts of a malformed XML document, or customize the output by dropping the DOCTYPE declaration or XML declaration, the command provides several options to cater to your specific needs. By utilizing the command’s flexibility, you can transform messy XML documents into clean and well-formatted structures, greatly enhancing readability and facilitating further processing.
