How to use the command xmlstarlet (with examples)

XMLStarlet is a command-line XML/XSLT toolkit that allows you to perform various operations on XML documents. With XMLStarlet, you can format XML, select nodes using XPath, edit XML files, and more.

Use case 1: Format an XML document and print to stdout

Code:

xmlstarlet format path/to/file.xml

Motivation: Formatting an XML document can improve readability and make it easier to work with. By using the format command with XMLStarlet, you can reformat an XML document and print the formatted version to the standard output.

Explanation:

• xmlstarlet is the command itself.
• format is the subcommand used to format the XML document.
• path/to/file.xml is the path to the input XML file that you want to format.

Example output:

<?xml version="1.0"?>
<root>
  <element attribute="value">Text</element>
</root>

Use case 2: XML document can also be piped from stdin

Code:

cat path/to/file.xml | xmlstarlet format

Motivation: Piping the input XML document from stdin can be useful when you want to process XML data that doesn’t come from a file directly. This allows you to use XMLStarlet in combination with other commands to handle XML data in a more flexible way.

Explanation:

• cat path/to/file.xml reads the content of the XML file and sends it to the standard output.
• | is the pipe operator, which takes the output from the previous command and sends it as input to the next command.
• xmlstarlet format is the command that formats the XML data received from stdin.

Example output:

<?xml version="1.0"?>
<root>
  <element attribute="value">Text</element>
</root>

Use case 3: Print all nodes that match a given XPath

Code:

xmlstarlet select --template --copy-of xpath path/to/file.xml

Motivation: When working with large XML documents, it can be helpful to extract specific nodes that match a given XPath expression. XMLStarlet’s select command allows you to select nodes based on XPath and print them to the standard output.

Explanation:

• xmlstarlet select is the command used to select nodes from an XML document.
• --template option is used to specify that the selected nodes should be processed using an XSLT template.
• --copy-of xpath specifies the XPath expression to match the desired nodes.
• path/to/file.xml is the path to the input XML file.

Example output:

<element attribute="value">
  Text
</element>

Use case 4: Insert an attribute to all matching nodes, and print to stdout

Code:

xmlstarlet edit --insert xpath --type attr --name attribute_name --value attribute_value path/to/file.xml

Motivation: Sometimes, you may need to add attributes to specific nodes in an XML document. With XMLStarlet’s edit command, you can insert attributes to all nodes that match a given XPath expression and print the modified XML to the standard output without modifying the original file.

Explanation:

• xmlstarlet edit is the command used to modify an XML document.
• --insert xpath specifies the XPath expression to match the nodes where the attribute should be inserted.
• --type attr indicates that an attribute should be inserted.
• --name attribute_name specifies the name of the attribute to be inserted.
• --value attribute_value specifies the value of the attribute to be inserted.
• path/to/file.xml is the path to the input XML file.

Example output:

<root>
  <element attribute="value">Text</element>
</root>

Use case 5: Update the value of all matching nodes in place

Code:

xmlstarlet edit --inplace --update xpath --value new_value file.xml

Motivation: Sometimes, you may need to update the values of specific nodes in an XML document and persist the changes in the original file. XMLStarlet’s edit command with the --inplace option allows you to modify an XML document directly.

Explanation:

• xmlstarlet edit is the command used to modify an XML document.
• --inplace indicates that the modifications should be applied to the original file.
• --update xpath specifies the XPath expression to match the nodes to be updated.
• --value new_value specifies the new value to be set for the matching nodes.
• file.xml is the path to the input XML file.

Example output: The XML document in file.xml will be updated with the new value for the matching nodes.

Use case 6: Delete all matching nodes in place

Code:

xmlstarlet edit --inplace --delete xpath file.xml

Motivation: In certain scenarios, you may need to delete specific nodes from an XML document and persist the changes in the original file. With XMLStarlet’s edit command and the --delete option, you can remove nodes that match a given XPath expression directly from the XML file.

Explanation:

• xmlstarlet edit is the command used to modify an XML document.
• --inplace indicates that the modifications should be applied to the original file.
• --delete xpath specifies the XPath expression to match the nodes to be deleted.
• file.xml is the path to the input XML file.

Example output: The XML document in file.xml will be updated with the matching nodes removed.

Use case 7: Escape or unescape special XML characters in a given string

Code:

xmlstarlet [un]escape string

Motivation: XML documents require special characters to be escaped to ensure the document’s validity. XMLStarlet provides the [un]escape command, which allows you to escape or unescape special XML characters in a given string.

Explanation:

• xmlstarlet escape is the command to escape special XML characters.
• xmlstarlet unescape is the command to unescape special XML characters.
• string is the string that you want to escape or unescape.

Example output:

<root><element attribute="value">Text</element></root>

Use case 8: List a given directory as XML

Code:

xmlstarlet ls path/to/directory

Motivation: XMLStarlet’s ls command allows you to list the contents of a directory as XML. This can be useful when you want to generate an XML representation of a directory structure for further processing or analysis.

Explanation:

• xmlstarlet ls is the command to list a directory as XML.
• path/to/directory is the path to the directory you want to list. If no argument is provided, the current directory will be listed.

Example output:

<dir name=".">
  <file name="file1.txt"/>
  <file name="file2.txt"/>
  <dir name="subdir">
    <file name="file3.txt"/>
  </dir>
</dir>

Conclusion:

XMLStarlet is a powerful command-line XML/XSLT toolkit that provides various commands for working with XML documents. Whether you need to format XML, select nodes using XPath, edit XML files, or other XML-related tasks, XMLStarlet has got you covered. With the use cases demonstrated in this article, you can start leveraging XMLStarlet to manipulate and process XML data efficiently.