Support for the Ruby 2.4 series has ended. See here for reference.
The Ruby Standard Library is a vast collection of classes and modules that you can require in your code for additional features.
Below is an overview of libraries and extensions followed by a brief description.
Calculates a set of unique abbreviations for a given set of strings
Support for encoding and decoding binary data using a Base64 representation
Provides methods to measure and report the time used to execute code
Support for the Common Gateway Interface protocol
Provides Trigonometric and Transcendental functions for complex numbers
ConditionVariable
Augments the Mutex class
Provides an interface to read and write CSV files and data
Debugging functionality for Ruby
Provides three abilities to delegate method calls to an object
Distributed object system for Ruby
Module
for defining custom exceptions with specific messages
Require 'English.rb' to reference global variables with less cryptic names
An easy to use but powerful templating system for Ruby
Several file utility methods for copying, moving, removing, etc
This module supports top-down traversal of a set of file paths
Provides delegation of specified methods to a designated object
Parse command line options similar to the GNU C getopt_long()
Provides methods to manipulate IPv4 and IPv6 IP addresses
Interactive Ruby command-line tool for REPL (Read Eval Print Loop)
Provides a simple logging utility for outputting messages
Deprecated library that extends math operations
Module
used to generate a Makefile for C extensions
Represents a mathematical matrix.
Provides an object or module to use safely by more than one thread
Mixin to extend objects to be handled like a Mutex
Support for the File
Transfer Protocol
HTTP client api for Ruby
Ruby client api for Internet Message Access Protocol
Ruby client library for POP3
Simple Mail Transfer Protocol client library for Ruby
Provides a mechanism for publish/subscribe pattern in Ruby
An easy-to-use wrapper for Net::HTTP, Net::HTTPS and Net::FTP
Provides access to stdin, stdout and stderr when running other programs
Ruby-oriented class for command-line option analysis
Provides a PrettyPrinter for Ruby objects
Implements a pretty printing algorithm for readable structure
Prime numbers and factorization library
Runs the Ruby Profiler__
Provides a way to profile your Ruby application
Implements a file based persistence mechanism based on a Hash
Queue
Synchronized communication between threads
A LALR(1) parser generator written in Ruby.
Information of your configure and build of Ruby
Produces HTML and command-line documentation for Ruby
Replace Socket DNS with Resolv
Thread-aware DNS resolver library in Ruby
An XML toolkit for Ruby
The Linda distributed computing paradigm in Ruby
Family of libraries that support various formats of XML “feeds”
Package management framework for Ruby
A Ruby implementation of the C function scanf(3)
Interface for secure random number generator
Provides a class to deal with collections of unordered, unique values
An idiomatic Ruby interface for common UNIX shell commands
Manipulates strings with word parsing rules of UNIX Bourne shell
Implementation of the Singleton pattern for Ruby
A module that provides a two-phase lock with a counter
A utility class for managing temporary files
Watches for termination of multiple threads
Time
Extends the Time
class with methods for parsing and conversion
Auto-terminate potentially long-running operations in Ruby
Extends the Dir
class to manage the OS temporary file path
Outputs a source level execution trace of a Ruby program
Topological sorting using Tarjan's algorithm
Utilities to replace common UNIX commands
A Ruby module providing support for Uniform Resource Identifiers
Allows a referenced object to be garbage-collected
An HTTP server toolkit for Ruby
Remote Procedure Call over HTTP support for Ruby
Ruby client library for the Psych YAML implementation
Provides arbitrary-precision floating point decimal arithmetic
Provides coverage measurement for Ruby
A subclass of Object
includes Comparable
module for handling dates
Subclass of Date to handling dates, hours, minutes, seconds, offsets
Provides a wrapper for the UNIX-style Database Manager Library
Provides a framework for message digest libraries
Provides access to information typically stored in UNIX /etc directory
Loads constants defined in the OS fcntl.h C header file
A libffi wrapper for Ruby
Ruby extension for the GNU dbm (gdbm) library
IO
Extensions for Ruby IO
class, including wait and ::console
Implements Javascript Object
Notation for Ruby
Ruby extension for Network Kanji Filter
Extends ObjectSpace
module to add methods for internal statistics
Provides SSL, TLS and general purpose cryptography for Ruby
Representation of the name of a file or directory on the filesystem
A YAML parser and emitter for Ruby
Creates and manages pseudo terminals
Provides an interface for GNU Readline and Edit Line (libedit)
Ripper
Provides an interface for parsing Ruby programs into S-expressions
Provides a simple file-based key-value store with String
keys and values
Access underlying OS socket implementations
Pseudo I/O on String
objects
Provides lexical scanning operations on a String
Ruby interface for the POSIX system logging facility
Provides an interface for OLE Automation in Ruby
Ruby interface for the zlib compression/decompression library