Read and Write XML file in Ruby (with example)

This tutorial covers how to read, validate, and write XML files in the Ruby language.

In Ruby, Nokogiri is a popular gem module library to read and write XML files.

First, Install the gem module in a project using the below command.

gem install nokogiri

How to parse XML files in Ruby

Let’s have a users.xml file that contains the following content.

<users>
  <user >
    <id>1</id>
    <name>john</name>
    <!-- name of employee -->
    <salary>5000</salary>
    <!-- salary of employee -->
  </user>
  <user >
    <id>2</id>
    <name>Eric</name>
    <salary>3000</salary>
  </user>
  <user>
    <id>3</id>
    <name>Mark</name>
    <salary>5100</salary>
  </user>
</users>

require 'nokogiri'

file = 'users.xml'

begin
  # read XML file
  xml_string = File.read(file)
  object = Nokogiri::XML(xml_string)

  puts object.to_xml(indent: 2)
rescue => e
  puts "Failed to read XML file: #{e.message}"
end

In this example

Import module, require Nokogiri
Read the xml using File.read(), read into a ruby variable as a string, xml_string.
Convert the XML content to Ruby Object using the Nokogiri::XML method
the object is of type Nokogiri::XML::Document, representing XML document.
Convert a document to XML with pretty print using to_xml(indent: 2)
You can handle exceptions using begin and rescue to handle file io failures and invalid XML format.

How to Write to XML file in Ruby

This example converts the ruby object into XML format and writes to it.

require 'nokogiri'

xml_string =
  user: [
    { id=> 1, name=> "john", salary=> 5000 },
    { id=> 2, name=> "Eric", salary=> 3000 },
    { id=> 3, name=> "Mark", salary=> 5100 },
  ],
};

xml_builder = Nokogiri::XML::Builder.new do |xml|
  xml_string.each do |root, items|
    xml.send(root) do
      items.each do |key, value|
        if value.is_a?(Hash)
          value.each { |k, v| xml.send(k, v) }
        else
          xml.send(key, value)
        end
      end
    end
  end
end

file = 'result.xml'

begin
  # Write XML content to the file
  File.write(file, xml_builder.to_xml(indent: 2))
  puts "XML file created."
rescue => e
  puts "Failed to write XML file: #{e.message}"
end

In this example,

import Nokogiri module
Declare an XML object that contains the ruby object
Nokogiri::XML::Builder.new create XMl builder
Using the builder, Convert Ruby Object to XML formatted data
Finally, Write to a file using File.write with the to_xml(indent: 2) option
It creates an XML file
begin and rescue used to handle errors in writing to XML files.

XML - Ruby

How to parse XML files in Ruby

How to Write to XML file in Ruby