Using the XMLStarlet Toolkit: Query, edit, check, convert and transform XML documents (with examples)

XMLStarlet is a command-line tool that allows you to manipulate XML documents with ease. It provides a variety of subcommands to query, edit, check, convert, and transform XML files.

In this article, we will explore the different use cases of the XML command, including displaying general help, executing subcommands with input from files or URIs, executing subcommands using standard input/output, outputting to a file, and displaying the version of the XMLStarlet Toolkit.

Use case 1: Display general help

To display the general help, including the list of subcommands, you can use the following command:

xml --help

Motivation: You want to get an overview of the available subcommands and their usage.

Explanation: The --help option is used to display the general help menu. It lists all the available subcommands and provides a brief description of each.

Example output:

XMLStarlet Toolkit: Query, edit, check, convert and transform XML documents.
This command also has documentation about its subcommands, e.g. `xml validate`.
More information: <http://xmlstar.sourceforge.net/docs.php>.

Usage: xml [--version] [--help] <command> [<options>]

  Possible commands (some of the subcommands might not be available):
    c14n       canonicalization
    edit       Edit/Update XML document(s)
    el         Select element(s)
    fo         XSL-FO formatting object generation
    ls         List nodes
    pyx        convert XML to PYX format (based on ESIS - ISO 8879)
    sel        Select data value(s)
    sel1       Select data value(s) (only 1st occurrence is printed)
    tr         Translate, i.e. perform a find/replace on XML data values
    val        Validate (well-balanced) XML document
    ver        Display XML document(s) version
    x2d        Convert XML document to Diff format
    x2p        Convert XML document to Perl hash
    x2s        Convert XML document to XML Schema
    x2t        Apply XSLT stylesheet
    xd         Display XML document
    elid       Visit an element based on its Id

  Run `xml <command> --help' for help on a specific command.

Use case 2: Execute a subcommand with input from a file or URI, printing to stdout

To execute a subcommand with input from a file or URI and print the result to the standard output (stdout), you can use the following command:

xml subcommand options path/to/input.xml|URI

Motivation: You want to perform a specific operation on an XML document and view the result.

Explanation: Replace subcommand with the desired subcommand, options with the appropriate options for the subcommand, and path/to/input.xml|URI with the path to the input XML file or URI.

Example command:

xml sel -t -v "/root/element" sample.xml

In this example, sel is the subcommand used to select an element from the XML document specified by sample.xml. The -t option specifies that the output should be treated as a template string, and the -v option is used to print the value of the selected element.

Example output:

element value

Use case 3: Execute a subcommand using stdin and stdout

To execute a subcommand using standard input (stdin) and outputting the result to stdout, use the following command:

xml subcommand options

Motivation: You want to perform a specific operation on XML data provided through standard input.

Explanation: Replace subcommand with the desired subcommand and options with the appropriate options for the subcommand.

Example command:

echo "<root>data</root>" | xml sel -t -v "/"

In this example, the XML data <root>data</root> is provided to the sel subcommand through standard input. The -t option treats the output as a template string, and the -v option prints the selected value.

Example output:

data

Use case 4: Execute a subcommand with input from a file or URI and output to a file

To execute a subcommand with input from a file or URI and output the result to a file, use the following command:

xml subcommand options path/to/input.xml|URI > path/to/output

Motivation: You want to save the output of the XML operation to a file for further processing or analysis.

Explanation: Replace subcommand with the desired subcommand, options with the appropriate options for the subcommand, path/to/input.xml|URI with the path to the input XML file or URI, and path/to/output with the desired path for the output file.

Example command:

xml sel -t -v "/root/element" sample.xml > output.txt

In this example, the sel subcommand is used to select an element from the sample.xml file. The selected element’s value is then saved to the output.txt file.

Use case 5: Display help for a subcommand

To display help for a specific subcommand, use the following command:

xml subcommand --help

Motivation: You want detailed information about a specific subcommand and its usage.

Explanation: Replace subcommand with the desired subcommand for which you want to display help.

Example command:

xml sel --help

Example output:

Subcommand: sel

Summary: Select data value(s)

Usage: sel [-t] [-v value_expr] [-m match_expr] [file...]

Options:
     -t or --template        Treat input as a template

     -v or --value-of        Print value-of for xpath expr against each input node
     -c or --copy-of         Print copy-of for xpath expr against each input node
     -u or --unique          Print unique nodes of xpath expr for each input node
     -m or --match           Copy input to output if matching xpath expr
     -i or --if              If xpath evals to non-empty string, then do
     -e or --elem            Wrap with an element whose name is given by
     -n or --nl              Add newline at end when printing
     -1 or --once            Select only first node (if template option is used)
     -0 or --if0             If xpath evals to empty string, then do

     -B or --break-long      Break line if it's longer than given number of chars
     -C or --combo           Use ` to combine templates
     -F or --fix-nested-off  workaround for broken nested xsl:if support
     -H or --html            generate human-readable output
     -M or --match-name      Which part of the node to match against
     -N or --name            Name-prefix for hardly predictable namespace names
     -P or --prefix          Remove prefix
     -R or --reset           Reset counters
     -S or --indent-spaces   Number of spaces to use for each indentation level
     -T or --text            Show printable text nodes only
     -V or --value-of-nodes  Show children text nodes' value

     --without-comments     Skip comment nodes when copying the tree
     --without-ns-default   Do not output default namespace declarations
     --with-ns              Copy namespace nodes by default

XPath expression syntax:
     See 'xml sel --help' for more info on XPath expression syntax

Use case 6: Display the version of the XMLStarlet Toolkit

To display the version of the XMLStarlet Toolkit, use the following command:

xml --version

Motivation: You want to confirm which version of the XMLStarlet Toolkit you are using.

Explanation: The --version option displays the version number of the XMLStarlet Toolkit.

Example command:

xml --version

Example output:

XMLStarlet Toolkit version 1.6.1

Conclusion

XMLStarlet’s command-line tool offers great flexibility for manipulating, querying, and transforming XML documents. In this article, we explored different use cases, including displaying general help, executing subcommands with input from files or URIs, using standard input/output, outputting to a file, and displaying the version of the XMLStarlet Toolkit. By understanding these features, you can efficiently work with XML documents and automate XML-related tasks.