How to Use XMLStarlet Toolkit (with Examples)

The XMLStarlet Toolkit is a versatile command-line utility designed to simplify interactions with XML documents. Whether you need to query, edit, validate, or transform XML data, XMLStarlet offers various subcommands to streamline your workflow. It is an invaluable tool for developers and system administrators who work extensively with XML. Below, we explore multiple use cases of XMLStarlet with detailed examples to illustrate its functionality.

Use case 1: Display General Help, Including the List of Subcommands

Code:

xml --help

Motivation:

When starting with a new command-line tool, understanding the available subcommands and options is crucial. The --help flag provides a comprehensive overview of what XMLStarlet can do, which is essential for efficient navigation and use of the tool.

Explanation:

• xml: This initiates the XMLStarlet command.
• --help: This option displays the general help message, listing all the available subcommands and basic usage instructions.

Example Output:

Usage: xml [options] <command> <cmd-options>
Available commands are:
    ed     -- Edit/Update XML document(s)
    sel    -- Select data or query XML document(s) (XPATH, etc)
    val    -- Validate XML document(s) against DTD/XSD schema(s)
    ...
For more information about each command, use: xml <command> --help

Use case 2: Execute a Subcommand with Input from a File or URI, Printing to stdout

Code:

xml sel -t -v "/root/node" path/to/input.xml

Motivation:

Often, you need to extract specific data from an XML file to use in scripts or reports. This command allows you to query data from an XML file directly, making it easier to automate tasks that require XML data.

Explanation:

• xml: Starts the XMLStarlet command.
• sel: Selects data from the XML file.
• -t: Specifies the action type, in this case, text output.
• -v "/root/node": Specifies the XPath expression to select the node data.
• path/to/input.xml: Path to the XML file being queried.

Example Output:

NodeValue

Use case 3: Execute a Subcommand Using stdin and stdout

Code:

cat path/to/input.xml | xml sel -t -v "/root/node"

Motivation:

Piping data between commands is a common practice to enhance processing efficiency in shell scripting. This example demonstrates how stdin can be utilized to pass input to the XMLStarlet command, thereby integrating XML data processing seamlessly into larger scripts.

Explanation:

• cat path/to/input.xml: Outputs the contents of the specified XML file.
• |: Pipes the output from the cat command to the next command.
• xml sel -t -v "/root/node": Extracts data using the selector (as previously explained).

Example Output:

NodeValue

Use case 4: Execute a Subcommand with Input from a File or URI and Output to a File

Code:

xml sel -t -v "/root/node" path/to/input.xml > path/to/output.txt

Motivation:

Redirecting output to a file is beneficial for logging purposes or when the queried data needs to be preserved for further analysis or processed by other tools. This command ensures that you can store data efficiently for future use.

Explanation:

• xml sel -t -v "/root/node": Same as in the previous examples, this queries data from the XML file.
• path/to/input.xml: Specifies the input XML file for the query.
• >: Redirects the output to another location, in this case, a file.
• path/to/output.txt: The destination file for the output.

Example Output:

# content of path/to/output.txt
NodeValue

Use case 5: Display Help for a Specific Subcommand

Code:

xml sel --help

Motivation:

Understanding how to use a specific subcommand is vital for leveraging its full capabilities. This command provides detailed information on using the sel (select) subcommand, including its options and examples.

Explanation:

• xml: Initializes the XMLStarlet command.
• sel: Specifies that help is needed for the ‘select’ subcommand.
• --help: Displays help documentation for the sel subcommand.

Example Output:

Usage: xml sel [options]...
Options are:
   -t  Choose a template for XML
   -v  Value-of XPath
   ...

Use case 6: Display Version

Code:

xml --version

Motivation:

Knowing the version of a tool is essential for compatibility and troubleshooting. This command helps ensure you are using a version of XMLStarlet that meets the requirements of your project or system.

Explanation:

• xml: Represents the XMLStarlet command.
• --version: Outputs the current version of XMLStarlet installed on your system.

Example Output:

XMLStarlet Toolkit: 1.6.1

Conclusion:

The XMLStarlet Toolkit is an indispensable command-line utility for efficiently managing and processing XML documents. By providing a variety of commands and options, it enables users to perform complex XML manipulations with ease. Each use case highlighted above showcases the flexibility and power of XMLStarlet, from querying and editing XML files to checking their validity against schemas, making it a must-have tool for XML-centric workflows.