Module: OpenURI::OpenRead

open provides ‘open’ for ::URI::HTTP and ::URI::FTP.

open takes optional 3 arguments as:

OpenURI::OpenRead#open([mode [, perm]] [, options]) [{|io| ... }]

open returns an IO-like object if block is not given. Otherwise it yields the IO object and return the value of the block. The IO object is extended with Meta.

mode and perm are the same as Kernel.open.

However, mode must be read mode because open doesn’t support write mode (yet). Also perm is ignored because it is meaningful only for file creation.

options must be a hash.

Each option with a string key specifies an extra header field for HTTP. I.e., it is ignored for FTP without HTTP proxy.

The hash may include other options, where keys are symbols:

:proxy

Synopsis:

:proxy => "http://proxy.foo.com:8000/"
:proxy => URI.parse("http://proxy.foo.com:8000/")
:proxy => true
:proxy => false
:proxy => nil

If :proxy option is specified, the value should be String, URI, boolean or nil.

When String or URI is given, it is treated as proxy URI.

When true is given or the option itself is not specified, environment variable ‘scheme_proxy’ is examined. ‘scheme’ is replaced by ‘http’, ‘https’ or ‘ftp’.

When false or nil is given, the environment variables are ignored and connection will be made to a server directly.

:proxy_http_basic_authentication

Synopsis:

:proxy_http_basic_authentication =>
  ["http://proxy.foo.com:8000/", "proxy-user", "proxy-password"]
:proxy_http_basic_authentication =>
  [URI.parse("http://proxy.foo.com:8000/"),
   "proxy-user", "proxy-password"]

If :proxy option is specified, the value should be an Array with 3 elements. It should contain a proxy URI, a proxy user name and a proxy password. The proxy URI should be a String, an URI or nil. The proxy user name and password should be a String.

If nil is given for the proxy URI, this option is just ignored.

If :proxy and :proxy_http_basic_authentication is specified, ArgumentError is raised.

:http_basic_authentication

Synopsis:

:http_basic_authentication=>[user, password]

If :http_basic_authentication is specified, the value should be an array which contains 2 strings: username and password. It is used for HTTP Basic authentication defined by RFC 2617.

:content_length_proc

Synopsis:

:content_length_proc => lambda {|content_length| ... }

If :content_length_proc option is specified, the option value procedure is called before actual transfer is started. It takes one argument, which is expected content length in bytes.

If two or more transfers are performed by HTTP redirection, the procedure is called only once for the last transfer.

When expected content length is unknown, the procedure is called with nil. This happens when the HTTP response has no Content-Length header.

:progress_proc

Synopsis:

:progress_proc => lambda {|size| ...}

If :progress_proc option is specified, the proc is called with one argument each time when ‘open’ gets content fragment from network. The argument size is the accumulated transferred size in bytes.

If two or more transfer is done by HTTP redirection, the procedure is called only one for a last transfer.

:progress_proc and :content_length_proc are intended to be used for progress bar. For example, it can be implemented as follows using Ruby/ProgressBar.

pbar = nil
open("http://...",
  :content_length_proc => lambda {|t|
    if t && 0 < t
      pbar = ProgressBar.new("...", t)
      pbar.file_transfer_mode
    end
  },
  :progress_proc => lambda {|s|
    pbar.set s if pbar
  }) {|f| ... }

:read_timeout

Synopsis:

:read_timeout=>nil     (no timeout)
:read_timeout=>10      (10 second)

:read_timeout option specifies a timeout of read for http connections.

:open_timeout

Synopsis:

:open_timeout=>nil     (no timeout)
:open_timeout=>10      (10 second)

:open_timeout option specifies a timeout of open for http connections.

:ssl_ca_cert

Synopsis:

:ssl_ca_cert=>filename or an Array of filenames

:ssl_ca_cert is used to specify CA certificate for SSL. If it is given, default certificates are not used.

:ssl_verify_mode

Synopsis:

:ssl_verify_mode=>mode

:ssl_verify_mode is used to specify openssl verify mode.

:ssl_min_version

Synopsis:

:ssl_min_version=>:TLS1_2

:ssl_min_version option specifies the minimum allowed SSL/TLS protocol version. See also OpenSSL::SSL::SSLContext#min_version=.

:ssl_max_version

Synopsis:

:ssl_max_version=>:TLS1_2

:ssl_max_version option specifies the maximum allowed SSL/TLS protocol version. See also OpenSSL::SSL::SSLContext#max_version=.

:ftp_active_mode

Synopsis:

:ftp_active_mode=>bool

:ftp_active_mode => true is used to make ftp active mode. Ruby 1.9 uses passive mode by default. Note that the active mode is default in Ruby 1.8 or prior.

:redirect

Synopsis:

:redirect=>bool

:redirect is true by default. :redirect => false is used to disable all HTTP redirects.

OpenURI::HTTPRedirect exception raised on redirection. Using true also means that redirections between http and ftp are permitted.

:max_redirects

Synopsis:

:max_redirects=>int

Number of HTTP redirects allowed before OpenURI::TooManyRedirects is raised. The default is 64.

:request_specific_fields

Synopsis:

:request_specific_fields => {}
:request_specific_fields => lambda {|url| ...}

:request_specific_fields option allows specifying custom header fields that are sent with the HTTP request. It can be passed as a Hash or a Proc that gets evaluated on each request and returns a Hash of header fields.

If a Hash is provided, it specifies the headers only for the initial request and these headers will not be sent on redirects.

If a Proc is provided, it will be executed for each request including redirects, allowing dynamic header customization based on the request URL. It is important that the Proc returns a Hash. And this Hash specifies the headers to be sent with the request.

For Example with Hash

URI.open("http://...",
         request_specific_fields: {"Authorization" => "token dummy"}) {|f| ... }

For Example with Proc:

URI.open("http://...",
         request_specific_fields: lambda { |uri|
           if uri.host == "example.com"
             {"Authorization" => "token dummy"}
           else
             {}
           end
         }) {|f| ... }