How to Use the 'xml format' Command (with Examples)

The ‘xml format’ command is an invaluable tool for developers, data analysts, and anyone working with XML or HTML documents. It is designed to reformat XML and HTML documents, making them easier to read and edit. The tool offers several options for customization, ranging from indenting using tabs or spaces, recovering data from malformed documents, and removing specific parts of the XML structure like the DOCTYPE declaration or XML declaration. This article will delve into various use cases of the ‘xml format’ command, illustrating how to leverage its features effectively.

Use Case 1: Format an XML Document, Indenting with Tabs

Code:

xml format --indent-tab path/to/input.xml|URI > path/to/output.xml

Motivation: When dealing with XML files, readability is crucial. Developers often encounter XML documents with inconsistent or non-existent indentation, making the document difficult to read and manage. This command reformats the entire document by indenting elements using tabs, enhancing readability.

Explanation:

• xml format: The command used to format XML documents.
• --indent-tab: This flag specifies that tabs should be used for indenting the XML elements.
• path/to/input.xml|URI: The path to the input XML file or a URI from which the XML can be fetched.
• > path/to/output.xml: Redirects the cleaned and formatted output to the specified XML file.

Example Output: Before formatting, an XML document might appear as a single, continuous, and complex line. After using the command, elements will be neatly indented with tabs, sectioning the content into a more manageable and readable structure.

Use Case 2: Format an HTML Document, Indenting with 4 Spaces

Code:

xml format --html --indent-spaces 4 path/to/input.html|URI > path/to/output.html

Motivation: HTML documents, much like XML documents, can suffer from poor structure and readability issues. Indenting with a precise number of spaces helps maintain a standard coding style across projects, often aligning with organizational guidelines.

Explanation:

• xml format: Initiates the formatting process.
• --html: Indicates that the input document is an HTML file rather than XML.
• --indent-spaces 4: Specifies that the document should be indented using 4 spaces for each level of hierarchy.
• path/to/input.html|URI: The path to the input HTML file or a URI.
• > path/to/output.html: Saves the formatted output to the specified file.

Example Output: Originally cluttered HTML will now appear with a clean, structured format, where each nested element is indented by 4 spaces, significantly enhancing the readability of the document.

Use Case 3: Recover Parsable Parts of a Malformed XML Document, Without Indenting

Code:

xml format --recover --noindent path/to/malformed.xml|URI > path/to/recovered.xml

Motivation: XML documents can sometimes be damaged or poorly formed, causing issues for parsers. This command can salvage as much recognizable data as possible, helping recover essential information from a corrupted file without additional formatting.

Explanation:

• xml format: Begins the formatting and recovery process.
• --recover: Attempts to recover and retain valid, parsable parts of a malformed XML document.
• --noindent: Ensures that no additional indentation is added, preserving the original format of the recovered parts as much as possible.
• path/to/malformed.xml|URI: Points to the broken XML document needing recovery.
• > path/to/recovered.xml: Directs the output to a new XML file with recovered content.

Example Output: A malformed XML file with broken or missing tags will be processed, with reparable parts extracted into a new file, though without any formatting applied to the recovered elements.

Use Case 4: Format an XML Document from stdin, Removing the DOCTYPE Declaration

Code:

cat path/to/input.xml | xml format --dropdtd > path/to/output.xml

Motivation: In some scenarios, such as legacy transformations or security concerns, it might be necessary to remove the DOCTYPE declaration from an XML. Processing from stdin allows quick handling without creating intermediate files.

Explanation:

• cat path/to/input.xml: Reads the input XML file and sends it to the standard input stream.
• | xml format: Pipes the input from stdin to the ‘xml format’ command.
• --dropdtd: Drops any DOCTYPE declaration from the document during formatting.
• > path/to/output.xml: Writes the reformatted document minus the DOCTYPE to an output file.

Example Output: An XML document with an unwanted DOCTYPE declaration will now be clean of this element, simplifying the document for specific applications that might restrict or not require them.

Use Case 5: Format an XML Document, Omitting the XML Declaration

Code:

xml format --omit-decl path/to/input.xml|URI > path/to/output.xml

Motivation: Omitting the XML declaration from documents can be necessary when embedding XML snippets within other documents that do not expect or support this header.

Explanation:

• xml format: The main command to format XML documents.
• --omit-decl: This option instructs the formatter to omit the standard <?xml version="1.0"?> declaration.
• path/to/input.xml|URI: Location of the input XML file or URL.
• > path/to/output.xml: Redirects the formatted XML without the declaration to the specified output.

Example Output: The XML document is reformatted with all standard elements, except for the typically included XML declaration, thus appearing ready for embedding.

Use Case 6: Display Help

Code:

xml format --help

Motivation: Understanding available commands and options is crucial for utilizing any command-line tool effectively. The help option provides a comprehensive overview of what can be achieved with ‘xml format’.

Explanation:

• xml format --help: Calls the help documentation for the command, listing all available flags with their descriptions.

Example Output: The terminal will display all options and explanations for the ‘xml format’ command, providing guidance on how to use each feature.

Conclusion:

The ‘xml format’ command is a robust utility for anyone managing XML or HTML documents. By employing different options and combinations, users can enhance document readability, recover data from malformed files, and prepare XML content for various uses. Whether for tab-indented readability, compliance with style guides, recovery from errors, or stripping out unwanted XML components, ‘xml format’ proves to be an indispensable tool in the XML manipulation toolkit.