Network and Web Libraries

---

Ruby provides two levels of access to network services. At a low level, you can access the basic socket support in the underlying operating system, which allows you to implement clients and servers for both connection-oriented and connectionless protocols. These are documented in the next section. Ruby also has libraries that provide higher-level access to specific application-level network protocols, such as FTP, HTTP, and so on. These are documented starting on page 482. Finally, the CGI libraries, documented beginning on page 497, provide server-side developers with a convenient interface for developing Web applications.

Socket-Level Access

Sockets are the endpoints of a bidirectional communications channel. Sockets may communicate within a process, between processes on the same machine, or between processes on different continents. Sockets may be implemented over a number of different channel types: Unix domain sockets, TCP, UDP, and so on. The socket library provides specific classes for handling the common transports as well as a generic interface for handling the rest. All functionality in the socket library is accessible through a single extension library. Access it using Sockets have their own vocabulary:

domain

The family of protocols that will be used as the transport mechanism. These values are constants such as PF_INET, PF_UNIX, PF_X25, and so on.

type

The type of communications between the two endpoints, typically SOCK_STREAM for connection-oriented protocols and SOCK_DGRAM for connectionless protocols.

protocol

Typically zero, this may be used to identify a variant of a protocol within a domain and type.

hostName

The identifier of a network interface:

• a string, which can be a host name, a dotted-quad address, or an IPV6 address in colon (and possibly dot) notation,
• the string ``<broadcast>'', which specifies an INADDR_BROADCAST address,
• a zero-length string, which specifies INADDR_ANY, or
• an Integer, interpreted as a binary address in host byte order.

port

(sometimes called service) Each server listens for clients calling on one or more ports. A port may be a Fixnum port number, a string containing a port number, or the name of a service.

Sockets are children of class IO. Once a socket has been successfully opened, the conventional I/O methods may be used. However, greater efficiency is sometimes obtained by using socket-specific methods. As with other I/O classes, socket I/O blocks by default. The hierarchy of the socket classes is shown in Figure 26.1 on page 471. For more information on the use of sockets, see your operating system documentation. You'll also find a comprehensive treatment in W. Richard Stevens, Unix Network Programming, Volumes 1 and 2 .

Index:

do_not_reverse_lookup do_not_reverse_lookup= lookup_order lookup_order= close_read close_write getpeername getsockname getsockopt recv send setsockopt shutdown

---

BasicSocket is an abstract base class for all other socket classes. This class and its subclasses often manipulate addresses using something called a struct sockaddr, which is effectively an opaque binary string.[In reality, it maps onto the underlying C-language struct sockaddr set of structures, documented in the man pages and in the books by Stevens.] Returns the value of the global reverse lookup flag. If set to true, queries on remote addresses will return the numeric address but not the host name. Sets the global reverse lookup flag. Returns the global address lookup order, one of: Sets the global address lookup order. Closes the readable connection on this socket. Closes the writable connection on this socket. Returns the struct sockaddr structure associated with the other end of this socket connection. Returns the struct sockaddr structure associated with aSession. Returns the value of the specified option. Receives up to len bytes from aSession. Sends aString over aSession. If specified, to is a struct sockaddr specifying the recipient address. flags are the sum or one or more of the MSG_ options (listed on page 478). Returns the number of characters sent. Sets a socket option. level is one of the socket-level options (listed on page 478). optname and optval are protocol specific---see your system documentation for details. Shuts down the receive (how == 0), or send (how == 1), or both (how == 2), parts of this socket.

Index:

getaddress addr peeraddr

---

Class IPSocket is a base class for sockets using IP as their transport. TCPSocket and UDPSocket are based on this class. Returns the dotted-quad IP address of hostName. Returns the domain, port, name, and IP address of aSession as a four-element array. The name will be returned as an address if the do_not_reverse_lookup flag is true. Returns the domain, port, name, and IP address of the peer.

Index:

gethostbyname new open recvfrom

---

Looks up hostName and returns its canonical name, an array containing any aliases, the address type (AF_INET), and the dotted-quad IP address. Opens a TCP connection to hostName on the port. Synonym for TCPSocket.new. Receives up to len bytes on the connection. flags is zero or more of the MSG_ options (listed on page 478). Returns a two-element array. The first element is the received data, the second is an array containing information about the peer.

Index:

new open close

---

Class SOCKSSocket supports connections based on the SOCKS protocol. Opens a SOCKS connection to port on hostName. Synonym for SOCKSSocket.new. Closes this SOCKS connection.

Index:

new open accept

---

A TCPServer accepts incoming TCP connections. Here is a Web server that listens on a given port and returns the time. Creates a new socket on the given interface (identified by hostName and port). If hostName is omitted, the server will listen on all interfaces on the current host (equivalent to an address of 0.0.0.0). Synonym for TCPServer.new. Waits for a connection on aSession, and returns a new TCPSocket connected to the caller. See the example on page 474.

Index:

new open bind connect recvfrom send

---

UDP sockets send and receive datagrams. In order to receive data, a socket must be bound to a particular port. You have two choices when sending data: you can connect to a remote UDP socket and thereafter send datagrams to that port, or you can specify a host and port for use with every packet you send. This example is a UDP server that prints the message it receives. It is called by both connectionless and connection-based clients. produces: Creates an endpoint for UDP communications, optionally specifying the address family. Synonym for UDPSocket.new. Associates the local end of the UDP connection with a given hostName and port. Must be used by servers to establish an accessible endpoint. Creates a connection to the given hostName and port. Subsequent UDPSocket#send requests that don't override the recipient will use this connection. Multiple connect requests may be issued on aSession: the most recent will be used by send. Receives up to len bytes from aSession. flags is zero or more of the MSG_ options (listed on page 478). The result is a two-element array containing the received data and information on the sender. See the example on page 475. The two-parameter form sends aString on an existing connection. The four-parameter form sends aString to port on hostName.

Index:

new open addr path peeraddr recvfrom

---

Class UNIXSocket supports interprocess communications using the Unix domain protocol. Although the underlying protocol supports both datagram and stream connections, the Ruby library provides only a stream-based connection. produces: Opens a new domain socket on path, which must be a pathname. Synonym for UNIXSocket.new. Returns the address family and path of this socket. Returns the path of this domain socket. Returns the address family and path of the server end of the connection. Receives up to len bytes from aSession. flags is zero or more of the MSG_ options (listed on page 478). The first element of the returned array is the received data, and the second contains (minimal) information on the sender.

Index:

new open accept

---

Class UNIXServer provides a simple Unix domain socket server. See UNIXSocket for example code. Creates a server on the given path. The corresponding file must not exist at the time of the call. Synonym for UNIXServer.new. Waits for a connection on the server socket and returns a new socket object for that connection. See the example for UNIXSocket on page 476.

Index:

for_fd getaddrinfo gethostbyaddr gethostbyname gethostname getnameinfo getservbyname new open pair socketpair accept bind connect listen recvfrom

---

Class Socket provides access to the underlying operating system socket implementation. It can be used to provide more operating system-specific functionality than the protocol-specific socket classes, but at the expense of greater complexity. In particular, the class handles addresses using struct sockaddr structures packed into Ruby strings, which can be a joy to manipulate. Class Socket defines constants for use throughout the socket library. Individual constants are available only on architectures that support the related facility.

Types:

SOCK_DGRAM, SOCK_PACKET, SOCK_RAW, SOCK_RDM, SOCK_SEQPACKET, SOCK_STREAM.

Protocol families:

PF_APPLETALK, PF_AX25, PF_INET6, PF_INET, PF_IPX, PF_UNIX, PF_UNSPEC.

Address families:

AF_APPLETALK, AF_AX25, AF_INET6, AF_INET, AF_IPX, AF_UNIX, AF_UNSPEC.

Lookup-order options:

LOOKUP_INET6, LOOKUP_INET, LOOKUP_UNSPEC.

Send/receive options:

MSG_DONTROUTE, MSG_OOB, MSG_PEEK.

Socket-level options:

SOL_ATALK, SOL_AX25, SOL_IPX, SOL_IP, SOL_SOCKET, SOL_TCP, SOL_UDP.

Socket options:

SO_BROADCAST, SO_DEBUG, SO_DONTROUTE, SO_ERROR, SO_KEEPALIVE, SO_LINGER, SO_NO_CHECK, SO_OOBINLINE, SO_PRIORITY, SO_RCVBUF, SO_REUSEADDR, SO_SNDBUF, SO_TYPE.

QOS options:

SOPRI_BACKGROUND, SOPRI_INTERACTIVE, SOPRI_NORMAL.

Multicast options:

IP_ADD_MEMBERSHIP, IP_DEFAULT_MULTICAST_LOOP, IP_DEFAULT_MULTICAST_TTL, IP_MAX_MEMBERSHIPS, IP_MULTICAST_IF, IP_MULTICAST_LOOP, IP_MULTICAST_TTL.

TCP options:

TCP_MAXSEG, TCP_NODELAY.

getaddrinfo error codes:

EAI_ADDRFAMILY, EAI_AGAIN, EAI_BADFLAGS, EAI_BADHINTS, EAI_FAIL, EAI_FAMILY, EAI_MAX, EAI_MEMORY, EAI_NODATA, EAI_NONAME, EAI_PROTOCOL, EAI_SERVICE, EAI_SOCKTYPE, EAI_SYSTEM.

ai_flags values:

AI_ALL, AI_CANONNAME, AI_MASK, AI_NUMERICHOST, AI_PASSIVE, AI_V4MAPPED_CFG.

Wraps an already open file descriptor into a socket object. Returns an array of arrays describing the given host and port (optionally qualified as shown). Each subarray contains the address family, port number, host name, host IP address, protocol family, socket type, and protocol. produces: Returns the host name, address family, and sockaddr component for the given address. Returns a four-element array containing the canonical host name, a subarray of host aliases, the address family, and the address portion of the sockaddr structure. Returns the name of the current host. Looks up the given address, which may be either a string containing a sockaddr or a three- or four-element array. If sockaddr is an array, it should contain the string address family, the port (or nil), and the host name or IP address. If a fourth element is present and not nil, it will be used as the host name. Returns a canonical hostname (or address) and port number as an array. Returns the port corresponding to the given service and protocol. Creates a socket using the given parameters. Synonym for Socket.new. Returns a pair of connected, anonymous sockets of the given domain, type, and protocol. Synonym for Socket.pair. Accepts an incoming connection returning an array containing a new Socket object and a string holding the struct sockaddr information about the caller. Binds to the given struct sockaddr, contained in a string. Connects to the given struct sockaddr, contained in a string. Listens for connections, using the specified aFixnum as the backlog. Receives up to len bytes from aSession. flags is zero or more of the MSG_ options. The first element of the result is the data received. The second element contains protocol-specific information on the sender.

Higher-Level Access

Ruby provides a set of classes to facilitate writing clients for:

• File Transfer Protocol (FTP)
• HyperText Transfer Protocol (HTTP)
• Post Office Protocol (POP)
• Simple Mail Transfer Protocol (SMTP)
• Telnet

HTTP, POP, and SMTP are layered on top of a helper class, lib/net/protocol. Although we don't document the Protocol class here, you should probably study it if you are considering writing your own network client.

Index:

new open Server commands close closed? connect debug_mode debug_mode= dir getbinaryfile gettextfile lastresp list login ls mtime passive passive= putbinaryfile puttextfile resume resume= retrbinary retrlines return_code storbinary storlines welcome

---

The net/ftp library implements a File Transfer Protocol (FTP) client. Creates and returns a new FTP object. If the host parameter is not nil, a connection is made to that host. Additionally, if the user parameter is not nil, the given user name, password, and (optionally) account are used to log in. See the description of FTP#login on page 484. A synonym for FTP.new, but with a mandatory host parameter. Issues the corresponding server command and returns the result. Closes the current connection. Returns true if the current connection is closed. Establishes an FTP connection to host, optionally overriding the default port. If the environment variable SOCKS_SERVER is set, sets up the connection through a SOCKS proxy. Raises an exception (typically Errno::ECONNREFUSED) if the connection cannot be established. Returns the current debug mode. If the debug mode is true, all traffic to and from the server is written to $stdout. Synonym for FTP#list. Retrieves remotefile in binary mode, storing the result in localfile. If callback or an associated block is supplied, calls it, passing in the retrieved data in blocksize chunks. Retrieves remotefile in ASCII (text) mode, storing the result in localfile. If callback or an associated block is supplied, calls it, passing in the retrieved data one line at a time. Returns the host's last response. Fetches a directory listing of files matching the given pattern(s). If a block is associated with the call, invokes it with each line of the result. Otherwise, returns the result as an array of strings. Logs into the remote host. aSession must have been previously connected. If user is the string ``anonymous'' and the password is nil, a password of user@host is synthesized. If the acct parameter is not nil, an FTP ACCT command is sent following the successful login. Raises an exception on error (typically Net::FTPPermError). Synonym for FTP#list. Returns the last-modified time of remoteFile, interpreting the server's response as a GMT time if local is false, or as a local time otherwise. Returns the state of the passive flag. Puts the connection into passive mode if true. Transfers localfile to the server in binary mode, storing the result in remotefile. If callback or an associated block is supplied, calls it, passing in the transmitted data in blocksize chunks. Transfers localfile to the server in ASCII (text) mode, storing the result in remotefile. If callback or an associated block is supplied, calls it, passing in the transmitted data one line at a time. Returns the status of the resume flag (see FTP#resume=). Default is false. Sets the status of the resume flag. When resume is true, partially received files will resume where they left off, instead of starting from the beginning again. This is done by sending a REST command (RESTart incomplete transfer) to the server. Puts the connection into binary (image) mode, issues the given command, and fetches the data returned, passing it to the associated block in chunks of blocksize characters. Note that cmd is a server command (such as ``RETR myfile''). Puts the connection into ASCII (text) mode, issues the given command, and passes the resulting data, one line at a time, to the associated block. If no block is given, prints the lines. Note that cmd is a server command (such as ``RETR myfile''). Returns the return code from the last operation. Puts the connection into binary (image) mode, issues the given server-side command (such as ``STOR myfile''), and sends the contents of the file named fileName to the server. If the optional block is given, or if the callBack parameter is a Proc, also passes it the data, in chunks of blocksize characters. Puts the connection into ASCII (text) mode, issues the given server-side command (such as ``STOR myfile''), and sends the contents of the file named fileName to the server, one line at a time. If the optional block is given, or if the callBack parameter is a Proc, also passes it the lines. Returns the host's welcome message.

Index:

new port start get head post start

---

produces: The net/http library provides a simple client to fetch headers and Web page contents using the HTTP protocol. The get, post, and head requests raise exceptions on any error, including some HTTP status responses that would normally be considered recoverable. There are two ways of handling these.

1. Each method has a corresponding version get2, post2, or head2 that does not raise an exception. These versions are documented in the source.
2. Recoverable errors raise a Net::ProtoRetriableError exception. This exception contains a data attribute containing the response returned by the server.

The code below illustrates the handling of an HTTP status 301, a redirect. It uses Tomoyuki Kosimizu's URI package, available in the RAA. Creates and returns a new HTTP object. No connection is made until HTTP#start is called. Returns the default HTTP port (80). Equivalent to Net::HTTP.new(host, port).start. Retrieves headers and content from the specified path on the host specified when aSession was created. If specified, the headers parameter is a Hash containing additional header names and values to be sent with the request. The method returns a two-element array. The first element is an HTTPResponse object (documented in the next section). The second element is the page's content. The page's content is also passed to the << method of the dest parameter, or to the block if specified. This result is built network block by network block, not line by line. An exception is raised if an error is encountered. Multiple get calls may be made on aSession. Unless Protocol#finish is explicitly called, the connection will use the HTTP/1.1 keep-alive protocol, and will not close between requests. Retrieves headers from the specified path on the host specified when aSession was created. If specified, the headers parameter is a hash containing additional header names and values to be sent with the request. The method returns a hash of received headers. An exception is raised if an error is encountered. Multiple head calls may be made on aSession. Sends data to path using an HTTP POST request. headers is a hash containing additional headers. Assigns the result to data or to the block, as for Net_HTTP#get. Returns a two-element array containing an HTTPResponse object and the reply body. Establishes a connection to the host associated with aSession. (start is actually a method in Net::Protocol, but its use is required in HTTP objects.) In the block form, closes the session at the end of the block.

Index:

[ ] [ ]= code each key? message

---

Represents an HTTP response to a GET or POST request. Returns the header corresponding to the case-insensitive key. For example, a key of ``Content-type'' might return ``text/html''. Sets the header corresponding to the case-insensitive key. Returns the result code from the request (for example, ``404''). Iterates over all the header key-value pairs. Returns true only if a header with the given key exists. Returns the result message from the request (for example, ``Not found'').

Index:

new each finish mails start

---

produces: The net/pop library provides a simple client to fetch and delete mail on a Post Office Protocol (POP) server. The class Net::POP3 is used to access a POP server, returning a list of Net::POPMail objects, one per message stored on the server. These POPMail objects are then used to fetch and/or delete individual messages. The library also provides an alternative to the POP3 class that performs APOP authentication. Creates and returns a new POP3 object. No connection is made until POP3#start is called. Calls the associated block once for each e-mail stored on the server, passing in the corresponding POPMail object. Closes the pop connection. Some servers require that a connection is closed before they honor actions such as deleting mail. Returns false if the connection was never used. Returns an array of POPMail objects, where each object corresponds to an e-mail message stored on the server. Establishes a connection to the pop server, using the supplied username and password. Fetches a list of mail held on the server, which may be accessed using the POP3#mails and POP3#each methods. In block form, passes aSession to the block, and closes the connection using finish when the block terminates.

Index:

start

---

Establishes a connection to the APOP server.

Index:

all delete delete! header size top uidl

---

Fetches the corresponding e-mail from the server. With no argument or associated block, returns the e-mail as a string. With an argument but no block, appends the e-mail to dest by invoking dest << for each line in the e-mail. With an associated block, invokes the block once for each line in the e-mail. Deletes the e-mail from the server. Synonym for POPMail#delete. Returns the header lines for the corresponding e-mail message. Returns the size in bytes of the corresponding e-mail. Returns the header lines, plus lines message lines for the corresponding e-mail message. Returns the server-specific unique identifier for the corresponding e-mail.

Index:

new start ready sendmail start

---

The net/smtp library provides a simple client to send electronic mail using the Simple Mail Transfer Protocol (SMTP). Returns a new SMTP object connected to the given server and port. Equivalent to Net::SMTP.new(server, port).start(...). For an explanation of the remainder of the parameters, see the instance method Net_SMTP#start. Creates a new SMTP object. The domain parameter will be used in the initial HELO or EHLO transaction with the SMTP server. In the block form, the smtp object is passed into the block. When the block terminates, the session is closed. Equivalent to sendmail(from, to) { ...}. Sends header and body lines to the sendmail server. The from parameter is used as the sender's name in the MAIL FROM: command, and the to is either a string or an array of strings containing the recipients for the RCPT TO: command. The block is passed an adaptor object. Lines are sent to the server by calling the adaptor's write method. The terminating '.' and QUIT are sent automatically. Sends header and body lines to the sendmail server. The from parameter is used as the sender's name in the MAIL FROM: command, and to is either a string or an array of strings containing the recipients for the RCPT TO: command. Lines to be sent are fetched by invoking src .each. The terminating '.' and QUIT are sent automatically. Starts an SMTP session by connecting to the given domain (host). If acct and passwd are given, authentication will be attempted using the given authentication type (:plain or :cram_md5). If a block is supplied, it will be invoked with aSession as a parameter. The connection will be closed when the block terminates.

Index:

new binmode binmode= cmd login print telnetmode telnetmode= waitfor write

---

Connect to a localhost, run the ``date'' command, and disconnect. Monitor output as it occurs. We associate a block with each of the library calls; this block is called whenever data becomes available from the host. produces: Get the time from an NTP server. produces: The net/telnet library provides a complete implementation of a telnet client and includes features that make it a convenient mechanism for interacting with non-telnet services. Although the class description that follows indicates that Net::Telnet is a subclass of class Socket, this is a lie. In reality, the class delegates to Socket. The net effect is the same: the methods of Socket and its parent, class IO, are available through Net::Telnet objects. The methods new, cmd, login, and waitfor take an optional block. If present, the block is passed output from the server as it is received by the routine. This can be used to provide realtime output, rather than waiting for (for example) a login to complete before displaying the server's response. Connects to a server. options is a Hash with zero or more of the following: Returns the current value of the Binmode flag. Sets the Binmode flag, returning the new value. Sends a string to the server and waits (using a timeout) for a string that matches a pattern to be returned by the server. If the parameter is not a Hash, it is sent as a string to the server, and the pattern to match and the timeout are the Prompt and Timeout options given when aSession was created. If options is a Hash, then options['String'] is sent to the server. options['Match'] may be used to override the class Prompt parameter, and options['Timeout'] the timeout. The method returns the complete server response. If options is a Hash, a username is taken from options['Name'] and a password from options['Password']; otherwise, options is assumed to be the username, and password the password. The method waits for the server to send the string matching the pattern /login[:[visible space]]*\z/ and sends the username. If a password is given, it then waits for the server to send /Password[:[visible space]]*\z/ and sends the password. The method returns the full server response. Sends aString to the server, honoring Telnetmode, Binarymode, and any additional modes negotiated with the server. Returns the current value of the Telnetmode flag. Sets the Telnetmode flag, returning the new value. Waits for the server to respond with a string that matches a string or pattern. If options is not a Hash, it is compared against the cumulative server output as that output is received using options. ===. It is likely that you will want to use a regular expression in this case. If options is a Hash, then options['Match'], options['Prompt'], or options['String'] provides the match. In the latter case, the string will be converted to a regular expression before being used. options may also include the keys ``Timeout'' and ``Waittime'' to override the class options of the same names. Writes aString to the server with no translation.

CGI Development

Index:

escape escapeElement escapeHTML new parse pretty rfc1123_date unescape unescapeElement unescapeHTML [ ] cookies has_key? header keys out params

---

(The output of this script is shown in Figure 26.2 on page 499.) The CGI class provides support for programs used as a Web server CGI (Common Gateway Interface) script. It contains several methods for accessing fields in a CGI form, manipulating ``cookies'' and the environment, and outputting formatted HTML. Since environment variables contain a lot of useful information for a CGI script, CGI makes accessing them very easy---environment variables are accessible as attributes of CGI objects. For instance, cgi.auth_type returns the value of ENV["AUTH_TYPE"]. To create the method name, the environment variable name is translated to all lowercase, and the ``HTTP_'' prefix is stripped off. Thus, HTTP_USER_AGENT would be available as the method user_agent. Cookies are represented using a separate object of class CGI::Cookie, containing the following accessors: You create a cookie object using CGI_Cookie.new, which takes as arguments the accessors listed above, or CGI_Cookie.parse, which takes an encoded string and returns a cookie object. Returns a URL-encoded string made from the given argument, where unsafe characters (not alphanumeric, ``_'', ``-'', or ``.'') are encoded using ``%xx'' escapes. Returns a string made from the given argument with certain HTML-special characters escaped. The HTML elements given in elements will be escaped; other HTML elements will not be affected. produces: Returns a string made from the given argument with HTML-special characters (such as ``&'',``"'',``<'',``>'') quoted using ``&'', ``"'', ``<'', ``>'', and so on. Returns a new CGI object. If HTML output is required, the desired standards level must be given in aString (otherwise, no output routines will be created). The level may be one of: Parses a query string and returns a hash of its key-value pairs. Formats the given anHTMLString in a nice, readable format, optionally prefixing each line with aLeaderString. Returns a string representing the given time according to RFC 1123 (for instance, Mon, 1 Jan 2001 00:00:00 GMT). Returns a string containing ``unsafe'' characters made from the given URL-encoded argument, where unsafe characters were encoded using ``%'' escapes. Returns a string with the selected escaped HTML elements expanded to the actual characters. Returns a string made from the given argument with HTML-special quoted characters expanded to the actual characters. Returns the values of the given field names from the CGI form in an Array. See the note on multipart forms on page 503. Returns a new Hash object containing key-value pairs of cookie keys and values. Returns true if the form contains a field named aString. Returns a string containing the given headers (in the MOD_RUBY environment, the resulting header is sent immediately instead). If a hash is given as an argument, then the key-value pairs will be used to generate headers. Returns an array of all existing field names for the form. Generates HTML output using the results of the block as the content. Headers are generated as with CGI#header. See the example at the start of this section. Returns a new Hash object containing key-value pairs of field names and values from the form.

HTML Output Methods

In addition, CGI supports the following HTML output methods. Each of these methods is named after the corresponding HTML feature (or close to it). Those tags that require content (such as blockquote) take an optional block; the block should return a String that will be used as the content for the feature. These methods may take arguments as indicated, or as a hash with the given names as keys. \

---

a( url )
a( HREF => )
base( url )
base( HREF => )
blockquote( cite="" ) { aString }
blockquote( CITE => ) { aString }
caption( align=nil ) { aString }
caption( ALIGN => ) { aString }
checkbox( name=nil, value=nil, checked=nil )
checkbox( NAME, VALUE, CHECKED => )
checkbox_group( name=nil, [ items ]⁺ )
checkbox_group( NAME, VALUES => )

Items may be individual String names, or any of: an array of [ name, checked ], an array of [ value, name ], or an array of [ value, name, checked ]. The value for the hash key VALUES should be an array of these items.

file_field( name="", size=20, maxlength=nil )
file_field( NAME, SIZE, MAXLENGTH => )
form( method="post", action=nil, enctype="application/x-www-form-urlencoded" ) { aStr }
form( METHOD, ACTION, ENCTYPE => ) { aStr }
hidden( name="", value=nil )
hidden( NAME, VALUE => )
html( ) { aString }
html( PRETTY, DOCTYPE => ) { aString }
img_button( src="", name=nil, alt=nil )
img_button( SRC, NAME, ALT => )
img( src="", alt="", width=nil, height=nil )
img( SRC, ALT, WIDTH, HEIGHT => )
multipart_form( action=nil, enctype="multipart/form-data" ) { aString }
multipart_form( METHOD, ACTION, ENCTYPE => ) { aString }
password_field( name="", value=nil, size=40, maxlength=nil )
password_field( NAME, VALUE, SIZE, MAXLENGTH => )
popup_menu( name="", items )
popup_menu( NAME, SIZE, MULTIPLE, VALUES (array of items) => )

Items may be individual String names, or any of: an array of [ name, selected ], an array of [ value, name ], or an array of [ value, name, selected ]. The value for the hash key VALUES should be an array of these items.

radio_button( name="", value=nil, checked=nil )
radio_button( NAME, VALUE, CHECKED => )
radio_group( name="", items )
radio_group( NAME, VALUES (array of items) => )

Items may be individual String names, or any of: an array of [ name, selected ], an array of [ value, name ], or an array of [ value, name, selected ]. The value for the hash key VALUES should be an array of these items.

reset( value=nil, name=nil )
reset( VALUE, NAME => )
scrolling_list( alias for popup_menu )
scrolling_list( => )
submit( value=nil, name=nil )
submit( VALUE, NAME => )
text_field( name="", value=nil, size=40, maxlength=nil )
text_field( NAME, VALUE, SIZE, MAXLENGTH => )
textarea( name="", cols=70, rows=10 )
textarea( NAME, COLS, ROWS => ) \

---

In addition, all HTML tags are supported as methods, including title, head, body, br, pre, and so on. The block given to the method must return a String, which will be used as the content for that tag type. Not all tags require content: <P>, for example, does not. The available tags vary according to the supported HTML level---Table 26.1 on page 503 lists the complete set. For these methods, you can pass in a hash with attributes for the given tag. For instance, you might pass in 'BORDER'=>'5' to the table method to set the border width of the table.

Multipart Form Values

When dealing with a multipart form, the array returned by CGI#[] is composed of objects of class Tempfile, with the following dynamically added methods:

Index:

new [ ] [ ]= delete update

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A CGI::Session maintains a persistent state for web users in a CGI environment. Sessions may be memory-resident or may be stored on disk. See the discussion on page 146 for details. Returns a new session object for the CGI query. Options that may be given in aHash include: Returns the value for the given key. Sets the value for the given key. Calls the delete method of the underlying database manager. For FileStore, deletes the physical file containing the session. For MemoryStore, removes the session from memory. Calls the update method of the underlying database manager. For FileStore, writes the session data out to disk. Has no effect with MemoryStore.

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Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/)). Distribution of substantively modified versions of this document is prohibited without the explicit permission of the copyright holder. Distribution of the work or derivative of the work in any standard (paper) book form is prohibited unless prior permission is obtained from the copyright holder.