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This library allows for the identification of a file’s likely MIME content type. This is release 1.25, adding experimental caching and lazy loading functionality.
The caching and lazy loading features were initially implemented by Greg Brockman (gdb). As these features are experimental, they are disabled by default and must be enabled through the use of environment variables. The cache is invalidated on a per-version basis; the cache for version 1.25 will not be reused for version 1.26.
To use lazy loading, set the environment variable RUBY_MIME_TYPES_LAZY_LOAD to any value other than ‘false’. When using lazy loading, the initial startup of MIME::Types is around 12–25× faster than normal startup (on my system, normal startup is about 90 ms; lazy startup is about 4 ms). This isn’t generally useful, however, as the MIME::Types database has not been loaded. Lazy startup and load is just slightly faster—around 1 ms. The real advantage comes from using the cache.
To enable the cache, set the environment variable RUBY_MIME_TYPES_CACHE to a filename where MIME::Types will have read-write access. The first time a new version of MIME::Types is run using this file, it will be created, taking a little longer than normal. Subsequent loads using the same cache file will be approximately 3½× faster (25 ms) than normal loads. This can be combined with RUBY_MIME_TYPES_LAZY_LOAD, but this is not recommended in a multithreaded or multiprocess environment where all threads or processes will be using the same cache file.
As the caching interface is still experimental, the only values cached are the default MIME::Types database, not any custom MIME::Types added by users.
MIME types are used in MIME-compliant communications, as in e-mail or HTTP traffic, to indicate the type of content which is transmitted. MIME::Types provides the ability for detailed information about MIME entities (provided as a set of MIME::Type objects) to be determined and used programmatically. There are many types defined by RFCs and vendors, so the list is long but not complete; don’t hesitate to ask to add additional information. This library follows the IANA collection of MIME types (see below for reference).
MIME::Types for Ruby was originally based on MIME::Types for Perl by Mark Overmeer, copyright 2001 - 2009. As of version 1.15, the data format for the MIME::Type list has changed and the synchronization will no longer happen.
MIME::Types is built to conform to the MIME types of RFCs 2045 and 2231. It tracks the IANA registry (ftp) with some unofficial types added from the LTSW collection and added by the users of MIME::Types.
MIME types are used in MIME entities, as in email or HTTP traffic. It is useful at times to have information available about MIME types (or, inversely, about files). A MIME::Type stores the known information about one MIME type.
require 'mime/types' plaintext = MIME::Types['text/plain'] # returns [text/plain, text/plain] text = plaintext.first puts text.media_type # => 'text' puts text.sub_type # => 'plain' puts text.extensions.join(" ") # => 'txt asc c cc h hh cpp hpp dat hlp' puts text.encoding # => quoted-printable puts text.binary? # => false puts text.ascii? # => true puts text.obsolete? # => false puts text.registered? # => true puts text == 'text/plain' # => true puts MIME::Type.simplified('x-appl/x-zip') # => 'appl/zip' puts MIME::Types.any? { |type| type.content_type == 'text/plain' } # => true puts MIME::Types.all?(&:registered?) # => false
:include: Contributing.rdoc
:include: Licence.rdoc