In Files

  • cgi.rb
  • cgi/session.rb
  • cgi/session/pstore.rb

CGI

CGI class. See documentation for the file cgi.rb for an overview of 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 behaviour 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 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.

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 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.

Get cookie values

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.

Get cookie objects

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"}

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

require "cgi"
cgi = CGI.new("html3")  # add HTML generation methods
cgi.out() do
  cgi.html() do
    cgi.head{ cgi.title{"TITLE"} } +
    cgi.body() do
      cgi.form() do
        cgi.textarea("get_text") +
        cgi.br +
        cgi.submit
      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

Public Class Methods

escape(string) click to toggle source

URL-encode a string.

url_encoded_string = CGI::escape("'Stop!' said Fred")
   # => "%27Stop%21%27+said+Fred"
 
               # File cgi.rb, line 341
def CGI::escape(string)
  string.gsub(/([^ a-zA-Z0-9_.-]+)/n) do
    '%' + $1.unpack('H2' * $1.size).join('%').upcase
  end.tr(' ', '+')
end
            
escapeElement(string, *elements) click to toggle source

Escape only the tags of certain HTML elements in string.

Takes an element or elements or array of elements. Each element is specified by the name of the element, without angle brackets. This matches both the start and the end tag of that element. The attribute list of the open tag will also be escaped (for instance, the double-quotes surrounding attribute values).

print CGI::escapeElement('<BR><A HREF="url"></A>', "A", "IMG")
  # "<BR>&lt;A HREF=&quot;url&quot;&gt;&lt;/A&gt"

print CGI::escapeElement('<BR><A HREF="url"></A>', ["A", "IMG"])
  # "<BR>&lt;A HREF=&quot;url&quot;&gt;&lt;/A&gt"
 
               # File cgi.rb, line 417
def CGI::escapeElement(string, *elements)
  elements = elements[0] if elements[0].kind_of?(Array)
  unless elements.empty?
    string.gsub(/<\/?(?:#{elements.join("|")})(?!\w)(?:.|\n)*?>/ni) do
      CGI::escapeHTML($&)
    end
  else
    string
  end
end
            
escapeHTML(string) click to toggle source

Escape special characters in HTML, namely &"<>

CGI::escapeHTML('Usage: foo "bar" <baz>')
   # => "Usage: foo &quot;bar&quot; &lt;baz&gt;"
 
               # File cgi.rb, line 361
def CGI::escapeHTML(string)
  string.gsub(/&/n, '&amp;').gsub(/\"/n, '&quot;').gsub(/>/n, '&gt;').gsub(/</n, '&lt;')
end
            
new(type = "query") click to toggle source

Creates a new CGI instance.

type specifies which version of HTML to load the HTML generation methods for. The following versions of HTML are supported:

html3

HTML 3.x

html4

HTML 4.0

html4Tr

HTML 4.0 Transitional

html4Fr

HTML 4.0 with Framesets

If not specified, no HTML generation methods will be loaded.

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.

 
               # File cgi.rb, line 2265
def initialize(type = "query")
  if defined?(MOD_RUBY) && !ENV.key?("GATEWAY_INTERFACE")
    Apache.request.setup_cgi_env
  end

  extend QueryExtension
  @multipart = false
  if defined?(CGI_PARAMS)
    warn "do not use CGI_PARAMS and CGI_COOKIES"
    @params = CGI_PARAMS.dup
    @cookies = CGI_COOKIES.dup
  else
    initialize_query()  # set @params, @cookies
  end
  @output_cookies = nil
  @output_hidden = nil

  case type
  when "html3"
    extend Html3
    element_init()
    extend HtmlExtension
  when "html4"
    extend Html4
    element_init()
    extend HtmlExtension
  when "html4Tr"
    extend Html4Tr
    element_init()
    extend HtmlExtension
  when "html4Fr"
    extend Html4Tr
    element_init()
    extend Html4Fr
    element_init()
    extend HtmlExtension
  end
end
            
parse(query) click to toggle source

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

params = CGI::parse("query_string")
  # {"name1" => ["value1", "value2", ...],
  #  "name2" => ["value1", "value2", ...], ... }
 
               # File cgi.rb, line 896
def CGI::parse(query)
  params = Hash.new([].freeze)

  query.split(/[&;]/n).each do |pairs|
    key, value = pairs.split('=',2).collect{|v| CGI::unescape(v) }
    if params.has_key?(key)
      params[key].push(value)
    else
      params[key] = [value]
    end
  end

  params
end
            
pretty(string, shift = " ") click to toggle source

Prettify (indent) an HTML string.

string is the HTML string to indent. shift is the indentation unit to use; it defaults to two spaces.

print CGI::pretty("<HTML><BODY></BODY></HTML>")
  # <HTML>
  #   <BODY>
  #   </BODY>
  # </HTML>

print CGI::pretty("<HTML><BODY></BODY></HTML>", "\t")
  # <HTML>
  #         <BODY>
  #         </BODY>
  # </HTML>
 
               # File cgi.rb, line 1217
def CGI::pretty(string, shift = "  ")
  lines = string.gsub(/(?!\A)<(?:.|\n)*?>/n, "\n\\0").gsub(/<(?:.|\n)*?>(?!\n)/n, "\\0\n")
  end_pos = 0
  while end_pos = lines.index(/^<\/(\w+)/n, end_pos)
    element = $1.dup
    start_pos = lines.rindex(/^\s*<#{element}/ni, end_pos)
    lines[start_pos ... end_pos] = "__" + lines[start_pos ... end_pos].gsub(/\n(?!\z)/n, "\n" + shift) + "__"
  end
  lines.gsub(/^((?:#{Regexp::quote(shift)})*)__(?=<\/?\w)/n, '\1')
end
            
rfc1123_date(time) click to toggle source

Format a Time object as a String using the format specified by RFC 1123.

CGI::rfc1123_date(Time.now)
  # Sat, 01 Jan 2000 00:00:00 GMT
 
               # File cgi.rb, line 454
def CGI::rfc1123_date(time)
  t = time.clone.gmtime
  return format("%s, %.2d %s %.4d %.2d:%.2d:%.2d GMT",
              RFC822_DAYS[t.wday], t.day, RFC822_MONTHS[t.month-1], t.year,
              t.hour, t.min, t.sec)
end
            
unescape(string) click to toggle source

URL-decode a string.

string = CGI::unescape("%27Stop%21%27+said+Fred")
   # => "'Stop!' said Fred"
 
               # File cgi.rb, line 351
def CGI::unescape(string)
  string.tr('+', ' ').gsub(/((?:%[0-9a-fA-F]{2})+)/n) do
    [$1.delete('%')].pack('H*')
  end
end
            
unescapeElement(string, *elements) click to toggle source

Undo escaping such as that done by ::escapeElement

print CGI::unescapeElement(
        CGI::escapeHTML('<BR><A HREF="url"></A>'), "A", "IMG")
  # "&lt;BR&gt;<A HREF="url"></A>"

print CGI::unescapeElement(
        CGI::escapeHTML('<BR><A HREF="url"></A>'), ["A", "IMG"])
  # "&lt;BR&gt;<A HREF="url"></A>"
 
               # File cgi.rb, line 438
def CGI::unescapeElement(string, *elements)
  elements = elements[0] if elements[0].kind_of?(Array)
  unless elements.empty?
    string.gsub(/&lt;\/?(?:#{elements.join("|")})(?!\w)(?:.|\n)*?&gt;/ni) do
      CGI::unescapeHTML($&)
    end
  else
    string
  end
end
            
unescapeHTML(string) click to toggle source

Unescape a string that has been HTML-escaped

CGI::unescapeHTML("Usage: foo &quot;bar&quot; &lt;baz&gt;")
   # => "Usage: foo \"bar\" <baz>"
 
               # File cgi.rb, line 369
def CGI::unescapeHTML(string)
  string.gsub(/&(amp|quot|gt|lt|\#[0-9]+|\#x[0-9A-Fa-f]+);/n) do
    match = $1.dup
    case match
    when 'amp'                 then '&'
    when 'quot'                then '"'
    when 'gt'                  then '>'
    when 'lt'                  then '<'
    when /\A#0*(\d+)\z/n       then
      if Integer($1) < 256
        Integer($1).chr
      else
        if Integer($1) < 65536 and ($KCODE[0] == ?u or $KCODE[0] == ?U)
          [Integer($1)].pack("U")
        else
          "&##{$1};"
        end
      end
    when /\A#x([0-9a-f]+)\z/ni then
      if $1.hex < 256
        $1.hex.chr
      else
        if $1.hex < 65536 and ($KCODE[0] == ?u or $KCODE[0] == ?U)
          [$1.hex].pack("U")
        else
          "&#x#{$1};"
        end
      end
    else
      "&#{match};"
    end
  end
end
            

Public Instance Methods

header(options = "text/html") click to toggle source

Create an HTTP header block as a string.

Includes the empty line that ends the header block.

options can be a string specifying the Content-Type (defaults to text/html), or a hash of header key/value pairs. The following header keys are recognized:

type

the Content-Type header. Defaults to “text/html”

charset

the charset of the body, appended to the Content-Type header.

nph

a boolean value. If true, prepend protocol string and status code, and date; and sets default values for “server” and “connection” if not explicitly set.

status

the HTTP status code, returned as the Status header. See the list of available status codes below.

server

the server software, returned as the Server header.

connection

the connection type, returned as the Connection header (for instance, “close”.

length

the length of the content that will be sent, returned as the Content-Length header.

language

the language of the content, returned as the Content-Language header.

expires

the time on which the current content expires, as a Time object, returned as the Expires header.

cookie

a cookie or cookies, returned as one or more Set-Cookie headers. The value can be the literal string of the cookie; a CGI::Cookie object; an Array of literal cookie strings or Cookie objects; or a hash all of whose values are literal cookie strings or Cookie objects. These cookies are in addition to the cookies held in the @output_cookies field.

Other header lines can also be set; they are appended as key: value.

header
  # Content-Type: text/html

header("text/plain")
  # Content-Type: text/plain

header("nph"        => true,
       "status"     => "OK",  # == "200 OK"
         # "status"     => "200 GOOD",
       "server"     => ENV['SERVER_SOFTWARE'],
       "connection" => "close",
       "type"       => "text/html",
       "charset"    => "iso-2022-jp",
         # Content-Type: text/html; charset=iso-2022-jp
       "length"     => 103,
       "language"   => "ja",
       "expires"    => Time.now + 30,
       "cookie"     => [cookie1, cookie2],
       "my_header1" => "my_value"
       "my_header2" => "my_value")

The status codes are:

"OK"                  --> "200 OK"
"PARTIAL_CONTENT"     --> "206 Partial Content"
"MULTIPLE_CHOICES"    --> "300 Multiple Choices"
"MOVED"               --> "301 Moved Permanently"
"REDIRECT"            --> "302 Found"
"NOT_MODIFIED"        --> "304 Not Modified"
"BAD_REQUEST"         --> "400 Bad Request"
"AUTH_REQUIRED"       --> "401 Authorization Required"
"FORBIDDEN"           --> "403 Forbidden"
"NOT_FOUND"           --> "404 Not Found"
"METHOD_NOT_ALLOWED"  --> "405 Method Not Allowed"
"NOT_ACCEPTABLE"      --> "406 Not Acceptable"
"LENGTH_REQUIRED"     --> "411 Length Required"
"PRECONDITION_FAILED" --> "412 Precondition Failed"
"SERVER_ERROR"        --> "500 Internal Server Error"
"NOT_IMPLEMENTED"     --> "501 Method Not Implemented"
"BAD_GATEWAY"         --> "502 Bad Gateway"
"VARIANT_ALSO_VARIES" --> "506 Variant Also Negotiates"

This method does not perform charset conversion.

 
               # File cgi.rb, line 539
def header(options = "text/html")

  buf = ""

  case options
  when String
    options = { "type" => options }
  when Hash
    options = options.dup
  end

  unless options.has_key?("type")
    options["type"] = "text/html"
  end

  if options.has_key?("charset")
    options["type"] += "; charset=" + options.delete("charset")
  end

  options.delete("nph") if defined?(MOD_RUBY)
  if options.delete("nph") or
      (/IIS\/(\d+)/n.match(env_table['SERVER_SOFTWARE']) and $1.to_i < 5)
    buf += (env_table["SERVER_PROTOCOL"] or "HTTP/1.0")  + " " +
           (HTTP_STATUS[options["status"]] or options["status"] or "200 OK") +
           EOL +
           "Date: " + CGI::rfc1123_date(Time.now) + EOL

    unless options.has_key?("server")
      options["server"] = (env_table['SERVER_SOFTWARE'] or "")
    end

    unless options.has_key?("connection")
      options["connection"] = "close"
    end

    options.delete("status")
  end

  if options.has_key?("status")
    buf += "Status: " +
           (HTTP_STATUS[options["status"]] or options["status"]) + EOL
    options.delete("status")
  end

  if options.has_key?("server")
    buf += "Server: " + options.delete("server") + EOL
  end

  if options.has_key?("connection")
    buf += "Connection: " + options.delete("connection") + EOL
  end

  buf += "Content-Type: " + options.delete("type") + EOL

  if options.has_key?("length")
    buf += "Content-Length: " + options.delete("length").to_s + EOL
  end

  if options.has_key?("language")
    buf += "Content-Language: " + options.delete("language") + EOL
  end

  if options.has_key?("expires")
    buf += "Expires: " + CGI::rfc1123_date( options.delete("expires") ) + EOL
  end

  if options.has_key?("cookie")
    if options["cookie"].kind_of?(String) or
         options["cookie"].kind_of?(Cookie)
      buf += "Set-Cookie: " + options.delete("cookie").to_s + EOL
    elsif options["cookie"].kind_of?(Array)
      options.delete("cookie").each{|cookie|
        buf += "Set-Cookie: " + cookie.to_s + EOL
      }
    elsif options["cookie"].kind_of?(Hash)
      options.delete("cookie").each_value{|cookie|
        buf += "Set-Cookie: " + cookie.to_s + EOL
      }
    end
  end
  if @output_cookies
    for cookie in @output_cookies
      buf += "Set-Cookie: " + cookie.to_s + EOL
    end
  end

  options.each{|key, value|
    buf += key + ": " + value.to_s + EOL
  }

  if defined?(MOD_RUBY)
    table = Apache::request.headers_out
    buf.scan(/([^:]+): (.+)#{EOL}/n){ |name, value|
      warn sprintf("name:%s value:%s\n", name, value) if $DEBUG
      case name
      when 'Set-Cookie'
        table.add(name, value)
      when /^status$/ni
        Apache::request.status_line = value
        Apache::request.status = value.to_i
      when /^content-type$/ni
        Apache::request.content_type = value
      when /^content-encoding$/ni
        Apache::request.content_encoding = value
      when /^location$/ni
        if Apache::request.status == 200
          Apache::request.status = 302
        end
        Apache::request.headers_out[name] = value
      else
        Apache::request.headers_out[name] = value
      end
    }
    Apache::request.send_http_header
    ''
  else
    buf + EOL
  end

end
            
out(options = "text/html") click to toggle source

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

The header is provided by options, as for header(). The body of the document is that returned by the passed- in block. This block takes no arguments. It is required.

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" }

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

If ENV == “HEAD”, then only the header is outputted (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”.

 
               # File cgi.rb, line 703
def out(options = "text/html") # :yield:

  options = { "type" => options } if options.kind_of?(String)
  content = yield

  if options.has_key?("charset")
    require "nkf"
    case options["charset"]
    when /iso-2022-jp/ni
      content = NKF::nkf('-m0 -x -j', content)
      options["language"] = "ja" unless options.has_key?("language")
    when /euc-jp/ni
      content = NKF::nkf('-m0 -x -e', content)
      options["language"] = "ja" unless options.has_key?("language")
    when /shift_jis/ni
      content = NKF::nkf('-m0 -x -s', content)
      options["language"] = "ja" unless options.has_key?("language")
    end
  end

  options["length"] = content.length.to_s
  output = stdoutput
  output.binmode if defined? output.binmode
  output.print header(options)
  output.print content unless "HEAD" == env_table['REQUEST_METHOD']
end
            

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