MetaInspector is a gem for web scraping purposes.
You give it an URL, and it lets you easily get its title, links, images, charset, description, keywords, meta tags...
See it in action!
You can try MetaInspector live at this little demo: https://metainspectordemo.herokuapp.com
Installation
Install the gem from RubyGems:
gem install metainspector
If you're using it on a Rails application, just add it to your Gemfile and run bundle install
gem 'metainspector'
This gem is tested on Ruby versions 2.0.0, 2.1.8 and 2.2.4.
Usage
Initialize a MetaInspector instance for an URL, like this:
page = MetaInspector.new('http://sitevalidator.com')
If you don't include the scheme on the URL, http:// will be used by default:
page = MetaInspector.new('sitevalidator.com')
You can also include the html which will be used as the document to scrape:
page = MetaInspector.new("http://sitevalidator.com",
:document => "<html>...</html>")
Accessing response
You can check the status and headers from the response like this:
page.response.status # 200
page.response.headers # { "server"=>"nginx", "content-type"=>"text/html; charset=utf-8",
# "cache-control"=>"must-revalidate, private, max-age=0", ... }
Accessing scraped data
URL
page.url # URL of the page
page.tracked? # returns true if the url contains known tracking parameters
page.untracked_url # returns the url with the known tracking parameters removed
page.untrack! # removes the known tracking parameters from the url
page.scheme # Scheme of the page (http, https)
page.host # Hostname of the page (like, sitevalidator.com, without the scheme)
page.root_url # Root url (scheme + host, like http://sitevalidator.com/)
Head links
page.head_links # an array of hashes of all head/links
page.stylesheets # an array of hashes of all head/links where rel='stylesheet'
page.canonicals # an array of hashes of all head/links where rel='canonical'
page.feed # Get rss or atom links in meta data fields as array
Texts
page.title # title of the page from the head section, as string
page.best_title # best title of the page, from a selection of candidates
page.description # returns the meta description, or the first long paragraph if no meta description is found
Links
page.links.raw # every link found, unprocessed
page.links.all # every link found on the page as an absolute URL
page.links.http # every HTTP link found
page.links.non_http # every non-HTTP link found
page.links.internal # every internal link found on the page as an absolute URL
page.links.external # every external link found on the page as an absolute URL
Images
page.images # enumerable collection, with every img found on the page as an absolute URL
page.images.with_size # a sorted array (by descending area) of [image_url, width, height]
page.images.best # Most relevant image, if defined with the og:image or twitter:image metatags. Fallback to the first page.images array element
page.images.favicon # absolute URL to the favicon
Meta tags
When it comes to meta tags, you have several options:
page.meta_tags # Gives you all the meta tags by type:
# (meta name, meta http-equiv, meta property and meta charset)
# As meta tags can be repeated (in the case of 'og:image', for example),
# the values returned will be arrays
#
# For example:
#
# {
'name' => {
'keywords' => ['one, two, three'],
'description' => ['the description'],
'author' => ['Joe Sample'],
'robots' => ['index,follow'],
'revisit' => ['15 days'],
'dc.date.issued' => ['2011-09-15']
},
'http-equiv' => {
'content-type' => ['text/html; charset=UTF-8'],
'content-style-type' => ['text/css']
},
'property' => {
'og:title' => ['An OG title'],
'og:type' => ['website'],
'og:url' => ['http://example.com/meta-tags'],
'og:image' => ['http://example.com/rock.jpg',
'http://example.com/rock2.jpg',
'http://example.com/rock3.jpg'],
'og:image:width' => ['300'],
'og:image:height' => ['300', '1000']
},
'charset' => ['UTF-8']
}
As this method returns a hash, you can also take only the key that you need, like in:
page.meta_tags['property'] # Returns:
# {
# 'og:title' => ['An OG title'],
# 'og:type' => ['website'],
# 'og:url' => ['http://example.com/meta-tags'],
# 'og:image' => ['http://example.com/rock.jpg',
# 'http://example.com/rock2.jpg',
# 'http://example.com/rock3.jpg'],
# 'og:image:width' => ['300'],
# 'og:image:height' => ['300', '1000']
# }
In most cases you will only be interested in the first occurrence of a meta tag, so you can use the singular form of that method:
page.meta_tag['name'] # Returns:
# {
# 'keywords' => 'one, two, three',
# 'description' => 'the description',
# 'author' => 'Joe Sample',
# 'robots' => 'index,follow',
# 'revisit' => '15 days',
# 'dc.date.issued' => '2011-09-15'
# }
Or, as this is also a hash:
page.meta_tag['name']['keywords'] # Returns 'one, two, three'
And finally, you can use the shorter meta
method that will merge the different keys so you have
a simpler hash:
page.meta # Returns:
#
# {
# 'keywords' => 'one, two, three',
# 'description' => 'the description',
# 'author' => 'Joe Sample',
# 'robots' => 'index,follow',
# 'revisit' => '15 days',
# 'dc.date.issued' => '2011-09-15',
# 'content-type' => 'text/html; charset=UTF-8',
# 'content-style-type' => 'text/css',
# 'og:title' => 'An OG title',
# 'og:type' => 'website',
# 'og:url' => 'http://example.com/meta-tags',
# 'og:image' => 'http://example.com/rock.jpg',
# 'og:image:width' => '300',
# 'og:image:height' => '300',
# 'charset' => 'UTF-8'
# }
This way, you can get most meta tags just like that:
page.meta['author'] # Returns "Joe Sample"
Please be aware that all keys are converted to downcase, so it's 'dc.date.issued'
and not 'DC.date.issued'
.
Misc
page.charset # UTF-8
page.content_type # content-type returned by the server when the url was requested
Other representations
You can also access most of the scraped data as a hash:
page.to_hash # { "url" => "http://sitevalidator.com",
"title" => "MarkupValidator :: site-wide markup validation tool", ... }
The original document is accessible from:
page.to_s # A String with the contents of the HTML document
And the full scraped document is accessible from:
page.parsed # Nokogiri doc that you can use it to get any element from the page
Options
Timeout & Retries
You can specify 2 different timeouts when requesting a page:
connection_timeout
sets the maximum number of seconds to wait to get a connection to the page.read_timeout
sets the maximum number of seconds to wait to read the page, once connected.
Both timeouts default to 20 seconds each.
You can also specify the number of retries
, which defaults to 3.
For example, this will time out after 10 seconds waiting for a connection, or after 5 seconds waiting to read its contents, and will retry 4 times:
page = MetaInspector.new('www.google', :connection_timeout => 10, :read_timeout => 5, :retries => 4)
If MetaInspector fails to fetch the page after it has exhausted its retries,
it will raise Faraday::TimeoutError
, which you can rescue in your
application code.
begin
page = MetaInspector.new(url)
rescue Faraday::TimeoutError
enqueue_for_future_fetch_attempt(url)
render_simple(url)
else
render_rich(page)
end
Redirections
By default, MetaInspector will follow redirects (up to a limit of 10).
If you want to disallow redirects, you can do it like this:
page = MetaInspector.new('facebook.com', :allow_redirections => false)
Headers
By default, the following headers are set:
{
'User-Agent' => "MetaInspector/#{MetaInspector::VERSION} (+https://github.com/jaimeiniesta/metainspector)",
'Accept-Encoding' => 'identity'
}
The Accept-Encoding
is set to identity
to avoid exceptions being raised on servers that return malformed compressed responses, as explained here.
If you want to override the default headers then use the headers
option:
# Set the User-Agent header
page = MetaInspector.new('example.com', :headers => {'User-Agent' => 'My custom User-Agent'})
Disabling SSL verification (or any other Faraday options)
Faraday can be passed options via :faraday_options
.
This is useful in cases where we need to customize the way we request the page, like for example disabling SSL verification, like this:
MetaInspector.new('https://example.com')
# Faraday::SSLError: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed
MetaInspector.new('https://example.com', faraday_options: { ssl: { verify: false } })
# Now we can access the page
HTML Content Only
MetaInspector will try to parse all URLs by default. If you want to raise an exception when trying to parse a non-html URL (one that has a content-type different than text/html), you can state it like this:
page = MetaInspector.new('sitevalidator.com', :html_content_only => true)
This is useful when using MetaInspector on web spidering. Although on the initial URL you'll probably have an HTML URL, following links you may find yourself trying to parse non-html URLs.
page = MetaInspector.new('http://example.com/image.png')
page.content_type # "image/png"
page.description # will returned a garbled string
page = MetaInspector.new('http://example.com/image.png', :html_content_only => true)
page.content_type # "image/png"
page.description # raises an exception
URL Normalization
By default, URLs are normalized using the Addressable gem. For example:
# Normalization will add a default scheme and a trailing slash...
page = MetaInspector.new('sitevalidator.com')
page.url # http://sitevalidator.com/
# ...and it will also convert international characters
page = MetaInspector.new('http://www.詹姆斯.com')
page.url # http://www.xn--8ws00zhy3a.com/
While this is generally useful, it can be tricky sometimes.
You can disable URL normalization by passing the normalize_url: false
option.
Image downloading
When you ask for the largest image on the page with page.images.largest
, it will be determined by its height and width attributes on the HTML markup, and also by downloading a small portion of each image using the fastimage gem. This is really fast as it doesn't download the entire images, normally just the headers of the image files.
If you want to disable this, you can specify it like this:
page = MetaInspector.new('http://example.com', download_images: false)
Caching responses
MetaInspector can be configured to use Faraday::HttpCache to cache page responses. For that you should pass the faraday_http_cache
option with at least the :store
key, for example:
cache = ActiveSupport::Cache.lookup_store(:file_store, '/tmp/cache')
page = MetaInspector.new('http://example.com', faraday_http_cache: { store: cache })
Exception Handling
Web page scraping is tricky, you can expect to find different exceptions during the request of the page or the parsing of its contents. MetaInspector will encapsulate these exceptions on these main errors:
MetaInspector::TimeoutError
. When fetching a web page has taken too long.MetaInspector::RequestError
. When there has been an error on the request phase. Examples: page not found, SSL failure, invalid URI.MetaInspector::ParserError
. When there has been an error parsing the contents of the page. Example: trying to parse an image file.
Examples
You can find some sample scripts on the examples
folder, including a basic scraping and a spider that will follow external links using a queue. What follows is an example of use from irb:
$ irb
>> require 'metainspector'
=> true
>> page = MetaInspector.new('http://sitevalidator.com')
=> #<MetaInspector:0x11330c0 @url="http://sitevalidator.com">
>> page.title
=> "MarkupValidator :: site-wide markup validation tool"
>> page.meta['description']
=> "Site-wide markup validation tool. Validate the markup of your whole site with just one click."
>> page.meta['keywords']
=> "html, markup, validation, validator, tool, w3c, development, standards, free"
>> page.links.size
=> 15
>> page.links[4]
=> "/plans-and-pricing"
Contributing guidelines
You're more than welcome to fork this project and send pull requests. Just remember to:
- Create a topic branch for your changes.
- Add specs.
- Keep your fake responses as small as possible. For each change in
spec/fixtures
, a comment should be included explaining why it's needed. - Update
README.md
if needed (for example, when you're adding or changing a feature).
Thanks to all the contributors:
https://github.com/jaimeiniesta/metainspector/graphs/contributors
You can also come to chat with us on our Gitter room and Google group.
Related projects
- go-metainspector, a port of MetaInspector for Go.
- Node-MetaInspector, a port of MetaInspector for Node.
License
MetaInspector is released under the MIT license.