Simple Tumblr backup client using tumblr_client and saving in YAML format, created as an example.

tumblr_client_quick_yaml_archive.rb

require 'tumblr_client'
require 'fileutils'
require 'yaml'

@client = Tumblr::Client.new({
  :consumer_key       => "FILL",
  :consumer_secret    => "THESE",
  :oauth_token        => "FIELDS",
  :oauth_token_secret => "IN"
})
  
# You can get the consumer key and secret needed above by registering an 
# application here:
#   https://www.tumblr.com/oauth/apps
# and the OAuth data by feeding the key and secret into the API console, here:
#   https://api.tumblr.com/console/

def archive_blog(blog, offset: 0, limit: 20, sleep_for: 0.5, path: nil, **params)
  params.merge! offset: offset, limit: limit
  path = File.join(Dir.home, "tumblr", blog) unless path

  while true
    page = @client.posts(blog, params)

    if page['posts'].any?
      puts "Fetched #{page['posts'].count} posts at offset #{params[:offset]}. Saving..."

      save(page, path)
    end
    
    if page['posts'].count == params[:limit]
      params[:offset] += params[:limit]
      sleep sleep_for
    else # If we got too small a block of posts, we're done:
      params[:offset] += page['posts'].count
      puts "There appear to be no further posts to fetch. Final post count: #{params[:offset]}"
      File.write File.join(path, "metadata.yml"), page['blog'].to_yaml
      return path
    end
  end
end

def save(page, path)
  timestamp = Time.at(page['posts'].last['timestamp'])
  filename  = File.join path, "#{timestamp.strftime('%Y%m%d_%H%M%S')}.yml"

  FileUtils.mkdir_p(path) unless Dir.exist?(path)
  File.write(filename, page.to_yaml)
end