BasicSpecification
is an abstract class which implements some common code used by both Specification and StubSpecification.
Raised when there are conflicting gem specs loaded
Raised by the DependencyInstaller when a specific gem cannot be found
Represents an error communicating via HTTP.
The SourceList
represents the sources rubygems has been configured to use. A source may be created from an array of sources:
Gem::SourceList.from %w[https://rubygems.example https://internal.example]
Or by adding them:
sources = Gem::SourceList.new sources << 'https://rubygems.example'
The most common way to get a SourceList
is Gem.sources
.
Raised by Encoding
and String
methods when the string being transcoded contains a byte invalid for the either the source or target encoding.
Numeric
is the class from which all higher-level numeric classes should inherit.
Numeric
allows instantiation of heap-allocated objects. Other core numeric classes such as Integer
are implemented as immediates, which means that each Integer
is a single immutable object which is always passed by value.
a = 1 1.object_id == a.object_id #=> true
There can only ever be one instance of the integer 1
, for example. Ruby ensures this by preventing instantiation. If duplication is attempted, the same instance is returned.
Integer.new(1) #=> NoMethodError: undefined method `new' for Integer:Class 1.dup #=> 1 1.object_id == 1.dup.object_id #=> true
For this reason, Numeric
should be used when defining other numeric classes.
Classes which inherit from Numeric
must implement coerce
, which returns a two-member Array
containing an object that has been coerced into an instance of the new class and self
(see coerce
).
Inheriting classes should also implement arithmetic operator methods (+
, -
, *
and /
) and the <=>
operator (see Comparable
). These methods may rely on coerce
to ensure interoperability with instances of other numeric classes.
class Tally < Numeric def initialize(string) @string = string end def to_s @string end def to_i @string.size end def coerce(other) [self.class.new('|' * other.to_i), self] end def <=>(other) to_i <=> other.to_i end def +(other) self.class.new('|' * (to_i + other.to_i)) end def -(other) self.class.new('|' * (to_i - other.to_i)) end def *(other) self.class.new('|' * (to_i * other.to_i)) end def /(other) self.class.new('|' * (to_i / other.to_i)) end end tally = Tally.new('||') puts tally * 2 #=> "||||" puts tally > 1 #=> true
First, what’s elsewhere. Class Numeric:
Inherits from class Object.
Includes module Comparable.
Here, class Numeric provides methods for:
finite?
Returns true unless self
is infinite or not a number.
infinite?
Returns -1, nil
or +1, depending on whether self
is -Infinity<tt>, finite, or <tt>+Infinity
.
integer?
Returns whether self
is an integer.
negative?
Returns whether self
is negative.
nonzero?
Returns whether self
is not zero.
positive?
Returns whether self
is positive.
real?
Returns whether self
is a real value.
zero?
Returns whether self
is zero.
Returns:
-1 if self
is less than the given value.
0 if self
is equal to the given value.
1 if self
is greater than the given value.
nil
if self
and the given value are not comparable.
eql?
Returns whether self
and the given value have the same value and type.
-@
Returns the value of self
, negated.
abs2
Returns the square of self
.
ceil
Returns the smallest number greater than or equal to self
, to a given precision.
coerce
Returns array [coerced_self, coerced_other]
for the given other value.
denominator
Returns the denominator (always positive) of the Rational
representation of self
.
div
Returns the value of self
divided by the given value and converted to an integer.
divmod
Returns array [quotient, modulus]
resulting from dividing self
the given divisor.
floor
Returns the largest number less than or equal to self
, to a given precision.
polar
Returns the array [self.abs, self.arg]
.
quo
Returns the value of self
divided by the given value.
real
Returns the real part of self
.
rect
(aliased as rectangular
)Returns the array [self, 0]
.
remainder
Returns self-arg*(self/arg).truncate
for the given arg
.
round
Returns the value of self
rounded to the nearest value for the given a precision.
truncate
Returns self
truncated (toward zero) to a given precision.
Class Exception
and its subclasses are used to communicate between Kernel#raise
and rescue
statements in begin ... end
blocks.
An Exception
object carries information about an exception:
Its type (the exception’s class).
An optional descriptive message.
Optional backtrace information.
Some built-in subclasses of Exception
have additional methods: e.g., NameError#name
.
Two Ruby statements have default exception classes:
raise
: defaults to RuntimeError
.
rescue
: defaults to StandardError
.
When an exception has been raised but not yet handled (in rescue
, ensure
, at_exit
and END
blocks), two global variables are set:
$!
contains the current exception.
$@
contains its backtrace.
To provide additional or alternate information, a program may create custom exception classes that derive from the built-in exception classes.
A good practice is for a library to create a single “generic” exception class (typically a subclass of StandardError
or RuntimeError
) and have its other exception classes derive from that class. This allows the user to rescue the generic exception, thus catching all exceptions the library may raise even if future versions of the library add new exception subclasses.
For example:
class MyLibrary class Error < ::StandardError end class WidgetError < Error end class FrobError < Error end end
To handle both MyLibrary::WidgetError and MyLibrary::FrobError the library user can rescue MyLibrary::Error.
Exception
Classes The built-in subclasses of Exception
are:
fatal
Raised when a signal is received.
begin Process.kill('HUP',Process.pid) sleep # wait for receiver to handle signal sent by Process.kill rescue SignalException => e puts "received Exception #{e}" end
produces:
received Exception SIGHUP
BasicSocket
is the super class for all the Socket
classes.
BasicObject
is the parent class of all classes in Ruby. It’s an explicit blank class.
BasicObject
can be used for creating object hierarchies independent of Ruby’s object hierarchy, proxy objects like the Delegator
class, or other uses where namespace pollution from Ruby’s methods and classes must be avoided.
To avoid polluting BasicObject
for other users an appropriately named subclass of BasicObject
should be created instead of directly modifying BasicObject:
class MyObjectSystem < BasicObject end
BasicObject
does not include Kernel
(for methods like puts
) and BasicObject
is outside of the namespace of the standard library so common classes will not be found without using a full class path.
A variety of strategies can be used to provide useful portions of the standard library to subclasses of BasicObject
. A subclass could include Kernel
to obtain puts
, exit
, etc. A custom Kernel-like module could be created and included or delegation can be used via method_missing
:
class MyObjectSystem < BasicObject DELEGATE = [:puts, :p] def method_missing(name, *args, &block) return super unless DELEGATE.include? name ::Kernel.send(name, *args, &block) end def respond_to_missing?(name, include_private = false) DELEGATE.include?(name) or super end end
Access to classes and modules from the Ruby standard library can be obtained in a BasicObject
subclass by referencing the desired constant from the root like ::File
or ::Enumerator
. Like method_missing
, const_missing can be used to delegate constant lookup to Object
:
class MyObjectSystem < BasicObject def self.const_missing(name) ::Object.const_get(name) end end
These are the methods defined for BasicObject:
::new
Returns a new BasicObject instance.
Returns the boolean negation of self
: true
or false
.
Returns whether self
and the given object are not equal.
Returns whether self
and the given object are equivalent.
Returns the integer object identifier for self
.
Calls the method identified by the given symbol.
equal?
Returns whether self
and the given object are the same object.
instance_eval
Evaluates the given string or block in the context of self
.
instance_exec
Executes the given block in the context of self
, passing the given arguments.
method_missing
Method
called when an undefined method is called on self
.
singleton_method_added
Method
called when a singleton method is added to self
.
singleton_method_removed
Method
called when a singleton method is added removed from self
.
singleton_method_undefined
Method
called when a singleton method is undefined in self
.
Document-class: TracePoint
A class that provides the functionality of Kernel#set_trace_func
in a nice Object-Oriented API.
We can use TracePoint
to gather information specifically for exceptions:
trace = TracePoint.new(:raise) do |tp| p [tp.lineno, tp.event, tp.raised_exception] end #=> #<TracePoint:disabled> trace.enable #=> false 0 / 0 #=> [5, :raise, #<ZeroDivisionError: divided by 0>]
If you don’t specify the type of events you want to listen for, TracePoint
will include all available events.
Note do not depend on current event set, as this list is subject to change. Instead, it is recommended you specify the type of events you want to use.
To filter what is traced, you can pass any of the following as events
:
:line
execute an expression or statement on a new line
:class
start a class or module definition
:end
finish a class or module definition
:call
call a Ruby method
:return
return from a Ruby method
:c_call
call a C-language routine
:c_return
return from a C-language routine
:raise
raise an exception
:b_call
event hook at block entry
:b_return
event hook at block ending
:a_call
event hook at all calls (call
, b_call
, and c_call
)
:a_return
event hook at all returns (return
, b_return
, and c_return
)
:thread_begin
event hook at thread beginning
:thread_end
event hook at thread ending
:fiber_switch
event hook at fiber switch
:script_compiled
new Ruby code compiled (with eval
, load
or require
)
The objspace library extends the ObjectSpace
module and adds several methods to get internal statistic information about object/memory management.
You need to require 'objspace'
to use this extension module.
Generally, you *SHOULD NOT* use this library if you do not know about the MRI implementation. Mainly, this library is for (memory) profiler developers and MRI developers who need to know about MRI memory usage.
The ObjectSpace
module contains a number of routines that interact with the garbage collection facility and allow you to traverse all living objects with an iterator.
ObjectSpace
also provides support for object finalizers, procs that will be called when a specific object is about to be destroyed by garbage collection. See the documentation for ObjectSpace.define_finalizer
for important information on how to use this method correctly.
a = "A" b = "B" ObjectSpace.define_finalizer(a, proc {|id| puts "Finalizer one on #{id}" }) ObjectSpace.define_finalizer(b, proc {|id| puts "Finalizer two on #{id}" }) a = nil b = nil
produces:
Finalizer two on 537763470 Finalizer one on 537763480
OpenSSL
provides SSL
, TLS and general purpose cryptography. It wraps the OpenSSL library.
All examples assume you have loaded OpenSSL
with:
require 'openssl'
These examples build atop each other. For example the key created in the next is used in throughout these examples.
This example creates a 2048 bit RSA keypair and writes it to the current directory.
key = OpenSSL::PKey::RSA.new 2048 open 'private_key.pem', 'w' do |io| io.write key.to_pem end open 'public_key.pem', 'w' do |io| io.write key.public_key.to_pem end
Keys saved to disk without encryption are not secure as anyone who gets ahold of the key may use it unless it is encrypted. In order to securely export a key you may export it with a pass phrase.
cipher = OpenSSL::Cipher.new 'aes-256-cbc' pass_phrase = 'my secure pass phrase goes here' key_secure = key.export cipher, pass_phrase open 'private.secure.pem', 'w' do |io| io.write key_secure end
OpenSSL::Cipher.ciphers
returns a list of available ciphers.
A key can also be loaded from a file.
key2 = OpenSSL::PKey.read File.read 'private_key.pem' key2.public? # => true key2.private? # => true
or
key3 = OpenSSL::PKey.read File.read 'public_key.pem' key3.public? # => true key3.private? # => false
OpenSSL
will prompt you for your pass phrase when loading an encrypted key. If you will not be able to type in the pass phrase you may provide it when loading the key:
key4_pem = File.read 'private.secure.pem' pass_phrase = 'my secure pass phrase goes here' key4 = OpenSSL::PKey.read key4_pem, pass_phrase
RSA provides encryption and decryption using the public and private keys. You can use a variety of padding methods depending upon the intended use of encrypted data.
Asymmetric public/private key encryption is slow and victim to attack in cases where it is used without padding or directly to encrypt larger chunks of data. Typical use cases for RSA encryption involve “wrapping” a symmetric key with the public key of the recipient who would “unwrap” that symmetric key again using their private key. The following illustrates a simplified example of such a key transport scheme. It shouldn’t be used in practice, though, standardized protocols should always be preferred.
wrapped_key = key.public_encrypt key
A symmetric key encrypted with the public key can only be decrypted with the corresponding private key of the recipient.
original_key = key.private_decrypt wrapped_key
By default PKCS#1 padding will be used, but it is also possible to use other forms of padding, see PKey::RSA
for further details.
Using “private_encrypt” to encrypt some data with the private key is equivalent to applying a digital signature to the data. A verifying party may validate the signature by comparing the result of decrypting the signature with “public_decrypt” to the original data. However, OpenSSL::PKey
already has methods “sign” and “verify” that handle digital signatures in a standardized way - “private_encrypt” and “public_decrypt” shouldn’t be used in practice.
To sign a document, a cryptographically secure hash of the document is computed first, which is then signed using the private key.
signature = key.sign 'SHA256', document
To validate the signature, again a hash of the document is computed and the signature is decrypted using the public key. The result is then compared to the hash just computed, if they are equal the signature was valid.
if key.verify 'SHA256', signature, document puts 'Valid' else puts 'Invalid' end
If supported by the underlying OpenSSL
version used, Password-based Encryption should use the features of PKCS5
. If not supported or if required by legacy applications, the older, less secure methods specified in RFC 2898 are also supported (see below).
PKCS5
supports PBKDF2 as it was specified in PKCS#5 v2.0. It still uses a password, a salt, and additionally a number of iterations that will slow the key derivation process down. The slower this is, the more work it requires being able to brute-force the resulting key.
The strategy is to first instantiate a Cipher
for encryption, and then to generate a random IV plus a key derived from the password using PBKDF2. PKCS #5 v2.0 recommends at least 8 bytes for the salt, the number of iterations largely depends on the hardware being used.
cipher = OpenSSL::Cipher.new 'aes-256-cbc' cipher.encrypt iv = cipher.random_iv pwd = 'some hopefully not to easily guessable password' salt = OpenSSL::Random.random_bytes 16 iter = 20000 key_len = cipher.key_len digest = OpenSSL::Digest.new('SHA256') key = OpenSSL::PKCS5.pbkdf2_hmac(pwd, salt, iter, key_len, digest) cipher.key = key Now encrypt the data: encrypted = cipher.update document encrypted << cipher.final
Use the same steps as before to derive the symmetric AES key, this time setting the Cipher
up for decryption.
cipher = OpenSSL::Cipher.new 'aes-256-cbc' cipher.decrypt cipher.iv = iv # the one generated with #random_iv pwd = 'some hopefully not to easily guessable password' salt = ... # the one generated above iter = 20000 key_len = cipher.key_len digest = OpenSSL::Digest.new('SHA256') key = OpenSSL::PKCS5.pbkdf2_hmac(pwd, salt, iter, key_len, digest) cipher.key = key Now decrypt the data: decrypted = cipher.update encrypted decrypted << cipher.final
PKCS #5 is a password-based encryption standard documented at RFC2898. It allows a short password or passphrase to be used to create a secure encryption key. If possible, PBKDF2 as described above should be used if the circumstances allow it.
PKCS #5 uses a Cipher
, a pass phrase and a salt to generate an encryption key.
pass_phrase = 'my secure pass phrase goes here' salt = '8 octets'
First set up the cipher for encryption
encryptor = OpenSSL::Cipher.new 'aes-256-cbc' encryptor.encrypt encryptor.pkcs5_keyivgen pass_phrase, salt
Then pass the data you want to encrypt through
encrypted = encryptor.update 'top secret document' encrypted << encryptor.final
Use a new Cipher
instance set up for decryption
decryptor = OpenSSL::Cipher.new 'aes-256-cbc' decryptor.decrypt decryptor.pkcs5_keyivgen pass_phrase, salt
Then pass the data you want to decrypt through
plain = decryptor.update encrypted plain << decryptor.final
X509
Certificates This example creates a self-signed certificate using an RSA key and a SHA1 signature.
key = OpenSSL::PKey::RSA.new 2048 name = OpenSSL::X509::Name.parse '/CN=nobody/DC=example' cert = OpenSSL::X509::Certificate.new cert.version = 2 cert.serial = 0 cert.not_before = Time.now cert.not_after = Time.now + 3600 cert.public_key = key.public_key cert.subject = name
You can add extensions to the certificate with OpenSSL::SSL::ExtensionFactory to indicate the purpose of the certificate.
extension_factory = OpenSSL::X509::ExtensionFactory.new nil, cert cert.add_extension \ extension_factory.create_extension('basicConstraints', 'CA:FALSE', true) cert.add_extension \ extension_factory.create_extension( 'keyUsage', 'keyEncipherment,dataEncipherment,digitalSignature') cert.add_extension \ extension_factory.create_extension('subjectKeyIdentifier', 'hash')
The list of supported extensions (and in some cases their possible values) can be derived from the “objects.h” file in the OpenSSL
source code.
To sign a certificate set the issuer and use OpenSSL::X509::Certificate#sign
with a digest algorithm. This creates a self-signed cert because we’re using the same name and key to sign the certificate as was used to create the certificate.
cert.issuer = name cert.sign key, OpenSSL::Digest.new('SHA1') open 'certificate.pem', 'w' do |io| io.write cert.to_pem end
Like a key, a cert can also be loaded from a file.
cert2 = OpenSSL::X509::Certificate.new File.read 'certificate.pem'
Certificate#verify will return true when a certificate was signed with the given public key.
raise 'certificate can not be verified' unless cert2.verify key
A certificate authority (CA) is a trusted third party that allows you to verify the ownership of unknown certificates. The CA issues key signatures that indicate it trusts the user of that key. A user encountering the key can verify the signature by using the CA’s public key.
CA keys are valuable, so we encrypt and save it to disk and make sure it is not readable by other users.
ca_key = OpenSSL::PKey::RSA.new 2048 pass_phrase = 'my secure pass phrase goes here' cipher = OpenSSL::Cipher.new 'aes-256-cbc' open 'ca_key.pem', 'w', 0400 do |io| io.write ca_key.export(cipher, pass_phrase) end
A CA certificate is created the same way we created a certificate above, but with different extensions.
ca_name = OpenSSL::X509::Name.parse '/CN=ca/DC=example' ca_cert = OpenSSL::X509::Certificate.new ca_cert.serial = 0 ca_cert.version = 2 ca_cert.not_before = Time.now ca_cert.not_after = Time.now + 86400 ca_cert.public_key = ca_key.public_key ca_cert.subject = ca_name ca_cert.issuer = ca_name extension_factory = OpenSSL::X509::ExtensionFactory.new extension_factory.subject_certificate = ca_cert extension_factory.issuer_certificate = ca_cert ca_cert.add_extension \ extension_factory.create_extension('subjectKeyIdentifier', 'hash')
This extension indicates the CA’s key may be used as a CA.
ca_cert.add_extension \ extension_factory.create_extension('basicConstraints', 'CA:TRUE', true)
This extension indicates the CA’s key may be used to verify signatures on both certificates and certificate revocations.
ca_cert.add_extension \ extension_factory.create_extension( 'keyUsage', 'cRLSign,keyCertSign', true)
Root CA certificates are self-signed.
ca_cert.sign ca_key, OpenSSL::Digest.new('SHA1')
The CA certificate is saved to disk so it may be distributed to all the users of the keys this CA will sign.
open 'ca_cert.pem', 'w' do |io| io.write ca_cert.to_pem end
The CA signs keys through a Certificate Signing Request (CSR). The CSR contains the information necessary to identify the key.
csr = OpenSSL::X509::Request.new csr.version = 0 csr.subject = name csr.public_key = key.public_key csr.sign key, OpenSSL::Digest.new('SHA1')
A CSR is saved to disk and sent to the CA for signing.
open 'csr.pem', 'w' do |io| io.write csr.to_pem end
Upon receiving a CSR the CA will verify it before signing it. A minimal verification would be to check the CSR’s signature.
csr = OpenSSL::X509::Request.new File.read 'csr.pem' raise 'CSR can not be verified' unless csr.verify csr.public_key
After verification a certificate is created, marked for various usages, signed with the CA key and returned to the requester.
csr_cert = OpenSSL::X509::Certificate.new csr_cert.serial = 0 csr_cert.version = 2 csr_cert.not_before = Time.now csr_cert.not_after = Time.now + 600 csr_cert.subject = csr.subject csr_cert.public_key = csr.public_key csr_cert.issuer = ca_cert.subject extension_factory = OpenSSL::X509::ExtensionFactory.new extension_factory.subject_certificate = csr_cert extension_factory.issuer_certificate = ca_cert csr_cert.add_extension \ extension_factory.create_extension('basicConstraints', 'CA:FALSE') csr_cert.add_extension \ extension_factory.create_extension( 'keyUsage', 'keyEncipherment,dataEncipherment,digitalSignature') csr_cert.add_extension \ extension_factory.create_extension('subjectKeyIdentifier', 'hash') csr_cert.sign ca_key, OpenSSL::Digest.new('SHA1') open 'csr_cert.pem', 'w' do |io| io.write csr_cert.to_pem end
SSL
and TLS Connections Using our created key and certificate we can create an SSL
or TLS connection. An SSLContext is used to set up an SSL
session.
context = OpenSSL::SSL::SSLContext.new
SSL
Server An SSL
server requires the certificate and private key to communicate securely with its clients:
context.cert = cert context.key = key
Then create an SSLServer with a TCP server socket and the context. Use the SSLServer like an ordinary TCP server.
require 'socket' tcp_server = TCPServer.new 5000 ssl_server = OpenSSL::SSL::SSLServer.new tcp_server, context loop do ssl_connection = ssl_server.accept data = ssl_connection.gets response = "I got #{data.dump}" puts response ssl_connection.puts "I got #{data.dump}" ssl_connection.close end
SSL
client An SSL
client is created with a TCP socket and the context. SSLSocket#connect must be called to initiate the SSL
handshake and start encryption. A key and certificate are not required for the client socket.
Note that SSLSocket#close doesn’t close the underlying socket by default. Set
SSLSocket#sync_close to true if you want.
require 'socket' tcp_socket = TCPSocket.new 'localhost', 5000 ssl_client = OpenSSL::SSL::SSLSocket.new tcp_socket, context ssl_client.sync_close = true ssl_client.connect ssl_client.puts "hello server!" puts ssl_client.gets ssl_client.close # shutdown the TLS connection and close tcp_socket
An unverified SSL
connection does not provide much security. For enhanced security the client or server can verify the certificate of its peer.
The client can be modified to verify the server’s certificate against the certificate authority’s certificate:
context.ca_file = 'ca_cert.pem' context.verify_mode = OpenSSL::SSL::VERIFY_PEER require 'socket' tcp_socket = TCPSocket.new 'localhost', 5000 ssl_client = OpenSSL::SSL::SSLSocket.new tcp_socket, context ssl_client.connect ssl_client.puts "hello server!" puts ssl_client.gets
If the server certificate is invalid or context.ca_file
is not set when verifying peers an OpenSSL::SSL::SSLError
will be raised.
The Readline
module provides interface for GNU Readline
. This module defines a number of methods to facilitate completion and accesses input history from the Ruby interpreter. This module supported Edit Line(libedit) too. libedit is compatible with GNU Readline
.
Reads one inputted line with line edit by Readline.readline
method. At this time, the facilitatation completion and the key bind like Emacs can be operated like GNU Readline
.
require "readline" while buf = Readline.readline("> ", true) p buf end
The content that the user input can be recorded to the history. The history can be accessed by Readline::HISTORY
constant.
require "readline" while buf = Readline.readline("> ", true) p Readline::HISTORY.to_a print("-> ", buf, "\n") end
Documented by Kouji Takao <kouji dot takao at gmail dot com>.
The syslog package provides a Ruby interface to the POSIX system logging facility.
Syslog
messages are typically passed to a central logging daemon. The daemon may filter them; route them into different files (usually found under /var/log); place them in SQL databases; forward them to centralized logging servers via TCP or UDP; or even alert the system administrator via email, pager or text message.
Unlike application-level logging via Logger
or Log4r, syslog is designed to allow secure tamper-proof logging.
The syslog protocol is standardized in RFC 5424.
This module provides access to the zlib library. Zlib
is designed to be a portable, free, general-purpose, legally unencumbered – that is, not covered by any patents – lossless data-compression library for use on virtually any computer hardware and operating system.
The zlib compression library provides in-memory compression and decompression functions, including integrity checks of the uncompressed data.
The zlib compressed data format is described in RFC 1950, which is a wrapper around a deflate stream which is described in RFC 1951.
The library also supports reading and writing files in gzip (.gz) format with an interface similar to that of IO
. The gzip format is described in RFC 1952 which is also a wrapper around a deflate stream.
The zlib format was designed to be compact and fast for use in memory and on communications channels. The gzip format was designed for single-file compression on file systems, has a larger header than zlib to maintain directory information, and uses a different, slower check method than zlib.
See your system’s zlib.h for further information about zlib
Using the wrapper to compress strings with default parameters is quite simple:
require "zlib" data_to_compress = File.read("don_quixote.txt") puts "Input size: #{data_to_compress.size}" #=> Input size: 2347740 data_compressed = Zlib::Deflate.deflate(data_to_compress) puts "Compressed size: #{data_compressed.size}" #=> Compressed size: 887238 uncompressed_data = Zlib::Inflate.inflate(data_compressed) puts "Uncompressed data is: #{uncompressed_data}" #=> Uncompressed data is: The Project Gutenberg EBook of Don Quixote...
Class
tree (if you have GZIP_SUPPORT)
Include the English
library file in a Ruby script, and you can reference the global variables such as $_
using less cryptic names, listed below.
Without ‘English’:
$\ = ' -- ' "waterbuffalo" =~ /buff/ print $', $$, "\n"
With English:
require "English" $OUTPUT_FIELD_SEPARATOR = ' -- ' "waterbuffalo" =~ /buff/ print $POSTMATCH, $PID, "\n"
Below is a full list of descriptive aliases and their associated global variable:
$!
$@
$;
$;
$,
$,
$/
$/
$\
$\
$.
$.
$_
$>
$<
$$
$$
$?
$~
$=
$*
$&
$‘
$‘
$+