class CGI

Overview¶ ↑

The Common Gateway Interface (CGI) is a simple protocol for passing an HTTP request from a web server to a standalone program, and returning the output to the web browser. Basically, a CGI program is called with the parameters of the request passed in either in the environment (GET) or via $stdin (POST), and everything it prints to $stdout is returned to the client.

This file holds the CGI class. This class provides functionality for retrieving HTTP request parameters, managing cookies, and generating HTML output.

The file CGI::Session provides session management functionality; see that class for more details.

See www.w3.org/CGI/ for more information on the CGI protocol.

Introduction¶ ↑

CGI is a large class, providing several categories of methods, many of which are mixed in from other modules. Some of the documentation is in this class, some in the modules CGI::QueryExtension and CGI::HtmlExtension. See CGI::Cookie for specific information on handling cookies, and cgi/session.rb (CGI::Session) for information on sessions.

For queries, CGI provides methods to get at environmental variables, parameters, cookies, and multipart request data. For responses, CGI provides methods for writing output and generating HTML.

Read on for more details. Examples are provided at the bottom.

Queries¶ ↑

The CGI class dynamically mixes in parameter and cookie-parsing functionality, environmental variable access, and support for parsing multipart requests (including uploaded files) from the CGI::QueryExtension module.

Environmental Variables¶ ↑

The standard CGI environmental variables are available as read-only attributes of a CGI object. The following is a list of these variables:

AUTH_TYPE               HTTP_HOST          REMOTE_IDENT
CONTENT_LENGTH          HTTP_NEGOTIATE     REMOTE_USER
CONTENT_TYPE            HTTP_PRAGMA        REQUEST_METHOD
GATEWAY_INTERFACE       HTTP_REFERER       SCRIPT_NAME
HTTP_ACCEPT             HTTP_USER_AGENT    SERVER_NAME
HTTP_ACCEPT_CHARSET     PATH_INFO          SERVER_PORT
HTTP_ACCEPT_ENCODING    PATH_TRANSLATED    SERVER_PROTOCOL
HTTP_ACCEPT_LANGUAGE    QUERY_STRING       SERVER_SOFTWARE
HTTP_CACHE_CONTROL      REMOTE_ADDR
HTTP_FROM               REMOTE_HOST

For each of these variables, there is a corresponding attribute with the same name, except all lower case and without a preceding HTTP_. content_length and server_port are integers; the rest are strings.

Parameters¶ ↑

The method params() returns a hash of all parameters in the request as name/value-list pairs, where the value-list is an Array of one or more values. The CGI object itself also behaves as a hash of parameter names to values, but only returns a single value (as a String) for each parameter name.

For instance, suppose the request contains the parameter “favourite_colours” with the multiple values “blue” and “green”. The following behavior would occur:

cgi.params["favourite_colours"]  # => ["blue", "green"]
cgi["favourite_colours"]         # => "blue"

If a parameter does not exist, the former method will return an empty array, the latter an empty string. The simplest way to test for existence of a parameter is by the has_key? method.

Cookies¶ ↑

HTTP Cookies are automatically parsed from the request. They are available from the cookies() accessor, which returns a hash from cookie name to CGI::Cookie object.

Multipart requests¶ ↑

If a request’s method is POST and its content type is multipart/form-data, then it may contain uploaded files. These are stored by the QueryExtension module in the parameters of the request. The parameter name is the name attribute of the file input field, as usual. However, the value is not a string, but an IO object, either an IOString for small files, or a Tempfile for larger ones. This object also has the additional singleton methods:

local_path(): the path of the uploaded file on the local filesystem
original_filename(): the name of the file on the client computer
content_type(): the content type of the file

Responses¶ ↑

The CGI class provides methods for sending header and content output to the HTTP client, and mixes in methods for programmatic HTML generation from CGI::HtmlExtension and CGI::TagMaker modules. The precise version of HTML to use for HTML generation is specified at object creation time.

Writing output¶ ↑

The simplest way to send output to the HTTP client is using the out() method. This takes the HTTP headers as a hash parameter, and the body content via a block. The headers can be generated as a string using the http_header() method. The output stream can be written directly to using the print() method.

Generating HTML¶ ↑

Each HTML element has a corresponding method for generating that element as a String. The name of this method is the same as that of the element, all lowercase. The attributes of the element are passed in as a hash, and the body as a no-argument block that evaluates to a String. The HTML generation module knows which elements are always empty, and silently drops any passed-in body. It also knows which elements require matching closing tags and which don’t. However, it does not know what attributes are legal for which elements.

There are also some additional HTML generation methods mixed in from the CGI::HtmlExtension module. These include individual methods for the different types of form inputs, and methods for elements that commonly take particular attributes where the attributes can be directly specified as arguments, rather than via a hash.

Utility HTML escape and other methods like a function.¶ ↑

There are some utility tool defined in cgi/util.rb . And when include, you can use utility methods like a function.

Examples of use¶ ↑

Get form values¶ ↑

require "cgi"
cgi = CGI.new
value = cgi['field_name']   # <== value string for 'field_name'
  # if not 'field_name' included, then return "".
fields = cgi.keys            # <== array of field names

# returns true if form has 'field_name'
cgi.has_key?('field_name')
cgi.has_key?('field_name')
cgi.include?('field_name')

CAUTION! cgi['field_name'] returned an Array with the old cgi.rb(included in Ruby 1.6)

Get form values as hash¶ ↑

require "cgi"
cgi = CGI.new
params = cgi.params

cgi.params is a hash.

cgi.params['new_field_name'] = ["value"]  # add new param
cgi.params['field_name'] = ["new_value"]  # change value
cgi.params.delete('field_name')           # delete param
cgi.params.clear                          # delete all params

Save form values to file¶ ↑

require "pstore"
db = PStore.new("query.db")
db.transaction do
  db["params"] = cgi.params
end

Restore form values from file¶ ↑

require "pstore"
db = PStore.new("query.db")
db.transaction do
  cgi.params = db["params"]
end

Get multipart form values¶ ↑

require "cgi"
cgi = CGI.new
value = cgi['field_name']   # <== value string for 'field_name'
value.read                  # <== body of value
value.local_path            # <== path to local file of value
value.original_filename     # <== original filename of value
value.content_type          # <== content_type of value

and value has StringIO or Tempfile class methods.

require "cgi"
cgi = CGI.new
values = cgi.cookies['name']  # <== array of 'name'
  # if not 'name' included, then return [].
names = cgi.cookies.keys      # <== array of cookie names

and cgi.cookies is a hash.

require "cgi"
cgi = CGI.new
for name, cookie in cgi.cookies
  cookie.expires = Time.now + 30
end
cgi.out("cookie" => cgi.cookies) {"string"}

cgi.cookies # { "name1" => cookie1, "name2" => cookie2, ... }

require "cgi"
cgi = CGI.new
cgi.cookies['name'].expires = Time.now + 30
cgi.out("cookie" => cgi.cookies['name']) {"string"}

require "cgi"
cgi = CGI.new("html4")  # add HTML generation methods
cgi.out do
  cgi.html do
    cgi.head do
      cgi.title { "TITLE" }
    end +
    cgi.body do
      cgi.form("ACTION" => "uri") do
        cgi.p do
          cgi.textarea("get_text") +
          cgi.br +
          cgi.submit
        end
      end +
      cgi.pre do
        CGI.escapeHTML(
          "params: #{cgi.params.inspect}\n" +
          "cookies: #{cgi.cookies.inspect}\n" +
          ENV.collect do |key, value|
            "#{key} --> #{value}\n"
          end.join("")
        )
      end
    end
  end
end

# add HTML generation methods
CGI.new("html3")    # html3.2
CGI.new("html4")    # html4.01 (Strict)
CGI.new("html4Tr")  # html4.01 Transitional
CGI.new("html4Fr")  # html4.01 Frameset
CGI.new("html5")    # html5

Some utility methods¶ ↑

require 'cgi/util'
CGI.escapeHTML('Usage: foo "bar" <baz>')

Some utility methods like a function¶ ↑

require 'cgi/util'
include CGI::Util
escapeHTML('Usage: foo "bar" <baz>')
h('Usage: foo "bar" <baz>') # alias

Constants

CR: String for carriage return
EOL: Standard internet newline sequence
HTTP_STATUS: HTTP status codes.
LF: String for linefeed
MAX_MULTIPART_COUNT: Maximum number of request parameters when multipart
NEEDS_BINMODE: Whether processing will be required in binary vs text
PATH_SEPARATOR: Path separators in different environments.
VERSION

Attributes

accept_charset [R]

Return the accept character set for this CGI instance.

Public Class Methods

accept_charset ()

Source

# File lib/cgi/core.rb, line 759
def self.accept_charset
  @@accept_charset
end

Return the accept character set for all new CGI instances.

accept_charset= (accept_charset)

Source

# File lib/cgi/core.rb, line 764
def self.accept_charset=(accept_charset)
  @@accept_charset=accept_charset
end

Set the accept character set for all new CGI instances.

new(tag_maker) { block }

new(options_hash = {}) { block }

Source

# File lib/cgi/core.rb, line 850
def initialize(options = {}, &block) # :yields: name, value
  @accept_charset_error_block = block_given? ? block : nil
  @options={
    :accept_charset=>@@accept_charset,
    :max_multipart_length=>@@max_multipart_length
  }
  case options
  when Hash
    @options.merge!(options)
  when String
    @options[:tag_maker]=options
  end
  @accept_charset=@options[:accept_charset]
  @max_multipart_length=@options[:max_multipart_length]
  if defined?(MOD_RUBY) && !ENV.key?("GATEWAY_INTERFACE")
    Apache.request.setup_cgi_env
  end

  extend QueryExtension
  @multipart = false

  initialize_query()  # set @params, @cookies
  @output_cookies = nil
  @output_hidden = nil

  case @options[:tag_maker]
  when "html3"
    require_relative 'html'
    extend Html3
    extend HtmlExtension
  when "html4"
    require_relative 'html'
    extend Html4
    extend HtmlExtension
  when "html4Tr"
    require_relative 'html'
    extend Html4Tr
    extend HtmlExtension
  when "html4Fr"
    require_relative 'html'
    extend Html4Tr
    extend Html4Fr
    extend HtmlExtension
  when "html5"
    require_relative 'html'
    extend Html5
    extend HtmlExtension
  end
end

Create a new CGI instance.

tag_maker

This is the same as using the options_hash form with the value { :tag_maker => tag_maker } Note that it is recommended to use the options_hash form, since it also allows you specify the charset you will accept.

options_hash

A Hash that recognizes three options:

:accept_charset

specifies encoding of received query string. If omitted, @@accept_charset is used. If the encoding is not valid, a CGI::InvalidEncoding will be raised.

Example. Suppose @@accept_charset is “UTF-8”

when not specified:

cgi=CGI.new      # @accept_charset # => "UTF-8"

when specified as “EUC-JP”:

cgi=CGI.new(:accept_charset => "EUC-JP") # => "EUC-JP"

:tag_maker

String that specifies which version of the HTML generation methods to use. If not specified, no HTML generation methods will be loaded.

The following values are supported:

“html3”: HTML 3.x
“html4”: HTML 4.0
“html4Tr”: HTML 4.0 Transitional
“html4Fr”: HTML 4.0 with Framesets
“html5”: HTML 5

:max_multipart_length

Specifies maximum length of multipart data. Can be an Integer scalar or a lambda, that will be evaluated when the request is parsed. This allows more complex logic to be set when determining whether to accept multipart data (e.g. consult a registered users upload allowance)

Default is 128 * 1024 * 1024 bytes

cgi=CGI.new(:max_multipart_length => 268435456) # simple scalar

cgi=CGI.new(:max_multipart_length => -> {check_filesystem}) # lambda

block

If provided, the block is called when an invalid encoding is encountered. For example:

encoding_errors={}
cgi=CGI.new(:accept_charset=>"EUC-JP") do |name,value|
  encoding_errors[name] = value
end

Finally, if the CGI object is not created in a standard CGI call environment (that is, it can’t locate REQUEST_METHOD in its environment), then it will run in “offline” mode. In this mode, it reads its parameters from the command line or (failing that) from standard input. Otherwise, cookies and other parameters are parsed automatically from the standard CGI locations, which varies according to the REQUEST_METHOD.

parse (query)

Source

# File lib/cgi/core.rb, line 393
def self.parse(query)
  params = {}
  query.split(/[&;]/).each do |pairs|
    key, value = pairs.split('=',2).collect{|v| CGI.unescape(v) }

    next unless key

    params[key] ||= []
    params[key].push(value) if value
  end

  params.default=[].freeze
  params
end

Parse an HTTP query string into a hash of key=>value pairs.

params = CGI.parse("query_string")
  # {"name1" => ["value1", "value2", ...],
  #  "name2" => ["value1", "value2", ...], ... }

Public Instance Methods

header

Alias for: http_header

http_header

Source

Also aliased as: header

out(content_type_string='text/html')

out(headers_hash)

Source

# File lib/cgi/core.rb, line 367
def out(options = "text/html") # :yield:

  options = { "type" => options } if options.kind_of?(String)
  content = yield
  options["length"] = content.bytesize.to_s
  output = stdoutput
  output.binmode if defined? output.binmode
  output.print http_header(options)
  output.print content unless "HEAD" == env_table['REQUEST_METHOD']
end

Print an HTTP header and body to $DEFAULT_OUTPUT ($>)

content_type_string: If a string is passed, it is assumed to be the content type.
headers_hash: This is a Hash of headers, similar to that used by http_header.
block: A block is required and should evaluate to the body of the response.

Content-Length is automatically calculated from the size of the String returned by the content block.

If ENV['REQUEST_METHOD'] == "HEAD", then only the header is output (the content block is still required, but it is ignored).

If the charset is “iso-2022-jp” or “euc-jp” or “shift_jis” then the content is converted to this charset, and the language is set to “ja”.

Example:

cgi = CGI.new
cgi.out{ "string" }
  # Content-Type: text/html
  # Content-Length: 6
  #
  # string

cgi.out("text/plain") { "string" }
  # Content-Type: text/plain
  # Content-Length: 6
  #
  # string

cgi.out("nph"        => true,
        "status"     => "OK",  # == "200 OK"
        "server"     => ENV['SERVER_SOFTWARE'],
        "connection" => "close",
        "type"       => "text/html",
        "charset"    => "iso-2022-jp",
          # Content-Type: text/html; charset=iso-2022-jp
        "language"   => "ja",
        "expires"    => Time.now + (3600 * 24 * 30),
        "cookie"     => [cookie1, cookie2],
        "my_header1" => "my_value",
        "my_header2" => "my_value") { "string" }
   # HTTP/1.1 200 OK
   # Date: Sun, 15 May 2011 17:35:54 GMT
   # Server: Apache 2.2.0
   # Connection: close
   # Content-Type: text/html; charset=iso-2022-jp
   # Content-Length: 6
   # Content-Language: ja
   # Expires: Tue, 14 Jun 2011 17:35:54 GMT
   # Set-Cookie: foo
   # Set-Cookie: bar
   # my_header1: my_value
   # my_header2: my_value
   #
   # string

print (*options)

Source

# File lib/cgi/core.rb, line 383
def print(*options)
  stdoutput.print(*options)
end

Print an argument or list of arguments to the default output stream

cgi = CGI.new
cgi.print    # default:  cgi.print == $DEFAULT_OUTPUT.print

Private Instance Methods

_no_crlf_check (str)

Source

# File lib/cgi/core.rb, line 191
def _no_crlf_check(str)
  if str
    str = str.to_s
    raise "A HTTP status or header field must not include CR and LF" if str =~ /[\r\n]/
    str
  else
    nil
  end
end

env_table ()

Source

# File lib/cgi/core.rb, line 59
def env_table
  ENV
end

Synonym for ENV.

stdinput ()

Source

# File lib/cgi/core.rb, line 64
def stdinput
  $stdin
end

Synonym for $stdin.

stdoutput ()

Source

# File lib/cgi/core.rb, line 69
def stdoutput
  $stdout
end

Synonym for $stdout.

class CGI

Overview¶ ↑

Introduction¶ ↑

Queries¶ ↑

Environmental Variables¶ ↑

Parameters¶ ↑

Cookies¶ ↑

Multipart requests¶ ↑

Responses¶ ↑

Writing output¶ ↑

Generating HTML¶ ↑

Utility HTML escape and other methods like a function.¶ ↑

Examples of use¶ ↑

Get form values¶ ↑

Get form values as hash¶ ↑

Save form values to file¶ ↑

Restore form values from file¶ ↑

Get multipart form values¶ ↑

Get cookie values¶ ↑

Get cookie objects¶ ↑

Print http header and html string to $DEFAULT_OUTPUT ($>)¶ ↑

Some utility methods¶ ↑

Some utility methods like a function¶ ↑