How to use the command xml select (with examples)

The xml select command is a tool that allows you to select and extract specific elements or values from XML documents using XPATHs. It is part of the XMLStarlet package, which is a set of command-line tools for processing XML data.

Use case 1: Select and print the value of sub-element from matching elements

Code:

xml select --template --match "XPATH1" --value-of "XPATH2" path/to/input.xml|URI

Motivation: This use case is useful when you want to extract specific information from XML documents. By providing the XPATH1 to match the elements and XPATH2 to select the sub-element’s value, you can easily extract the desired data.

Explanation:

• --template: specifies that a template should be used for output.
• --match "XPATH1": specifies the XPATH1 expression to match the elements.
• --value-of "XPATH2": specifies the XPATH2 expression to select the value of the sub-element.
• path/to/input.xml|URI: the path or URI of the input XML document.

Example output:

Value1
Value2

Use case 2: Match and print the value as text with new-lines

Code:

xml select --text --template --match "XPATH1" --value-of "XPATH2" --nl path/to/input.xml|URI

Motivation: This use case is useful when you want to extract multiple values and display them as plain text with new lines between each value. It provides a more readable output format for further processing.

Explanation:

• --text: specifies that the output should be in plain text format.
• --nl: specifies to add new lines between each value.
• Other arguments have the same meaning as in the previous use case.

Example output:

Value1
Value2

Use case 3: Count the elements of XPATH1

Code:

xml select --template --value-of "count(XPATH1)" path/to/input.xml|URI

Motivation: This use case is useful when you want to determine the count of elements matching an XPATH expression. It allows you to quickly analyze the structure and content of an XML document.

Explanation:

• --value-of "count(XPATH1)": specifies an XPATH expression that counts the elements matching XPATH1.

Example output:

2

Use case 4: Count all nodes in one or more XML documents

Code:

xml select --text --template --inp-name --output " " --value-of "count(node())" --nl path/to/input1.xml|URI path/to/input2.xml|URI

Motivation: This use case is useful when you want to count all nodes (elements, text nodes, comments, etc.) in one or more XML documents. It provides an overview of the document’s structure and complexity.

Explanation:

• --inp-name: specifies to include the name of the input file or URI in the output.
• --output " ": specifies the separator between the input name and the count value (a space in this example).
• --value-of "count(node())": counts all nodes in the XML documents.

Example output:

input1.xml 10
input2.xml 5

Use case 5: Display help for the select subcommand

Code:

xml select --help

Motivation: This use case is useful when you need to quickly refer to the command’s usage and available options. It provides a concise help message with information on how to use the select subcommand.

Explanation:

• --help: displays the help information for the select subcommand.

Example output:

Usage: xmlstarlet select <global-options> <XML-SELECT-ARGS>
...
...

Conclusion:

The xml select command is a versatile tool for extracting specific elements or values from XML documents using XPATH expressions. It provides several useful options for customizing the output format and performing various operations on XML data. By understanding its different use cases and options, you can effectively extract and manipulate XML data to meet your specific requirements.