class Object

Object is the default root of all Ruby objects. Object inherits from BasicObject which allows creating alternate object hierarchies. Methods on Object are available to all classes unless explicitly overridden.

Object mixes in the Kernel module, making the built-in kernel functions globally accessible. Although the instance methods of Object are defined by the Kernel module, we have chosen to document them here for clarity.

When referencing constants in classes inheriting from Object you do not need to use the full namespace. For example, referencing File inside YourClass will find the top-level File class.

In the descriptions of Object’s methods, the parameter symbol refers to a symbol, which is either a quoted string or a Symbol (such as :name).

What’s Here

First, what’s elsewhere. Class Object:

Inherits from class BasicObject.
Includes module Kernel.

Here, class Object provides methods for:

Querying

!~: Returns true if self does not match the given object, otherwise false.
<=>: Returns 0 if self and the given object object are the same object, or if self == object; otherwise returns nil.
#===: Implements case equality, effectively the same as calling ==.
eql?: Implements hash equality, effectively the same as calling ==.
kind_of? (aliased as is_a?): Returns whether given argument is an ancestor of the singleton class of self.
instance_of?: Returns whether self is an instance of the given class.
instance_variable_defined?: Returns whether the given instance variable is defined in self.
method: Returns the Method object for the given method in self.
methods: Returns an array of symbol names of public and protected methods in self.
nil?: Returns false. (Only nil responds true to method nil?.)
#object_id: Returns an integer corresponding to self that is unique for the current process
private_methods: Returns an array of the symbol names of the private methods in self.
protected_methods: Returns an array of the symbol names of the protected methods in self.
public_method: Returns the Method object for the given public method in self.
public_methods: Returns an array of the symbol names of the public methods in self.
respond_to?: Returns whether self responds to the given method.
singleton_class: Returns the singleton class of self.
singleton_method: Returns the Method object for the given singleton method in self.
singleton_methods: Returns an array of the symbol names of the singleton methods in self.
define_singleton_method: Defines a singleton method in self for the given symbol method-name and block or proc.
extend: Includes the given modules in the singleton class of self.
public_send: Calls the given public method in self with the given argument.
#send: Calls the given method in self with the given argument.

Instance Variables

instance_variable_get: Returns the value of the given instance variable in self, or nil if the instance variable is not set.
instance_variable_set: Sets the value of the given instance variable in self to the given object.
instance_variables: Returns an array of the symbol names of the instance variables in self.
remove_instance_variable: Removes the named instance variable from self.

Other

clone: Returns a shallow copy of self, including singleton class and frozen state.
define_singleton_method: Defines a singleton method in self for the given symbol method-name and block or proc.
display: Prints self to the given IO stream or $stdout.
dup: Returns a shallow unfrozen copy of self.
enum_for (aliased as to_enum): Returns an Enumerator for self using the using the given method, arguments, and block.
extend: Includes the given modules in the singleton class of self.
freeze: Prevents further modifications to self.
hash: Returns the integer hash value for self.
inspect: Returns a human-readable string representation of self.
itself: Returns self.
method_missing: Method called when an undefined method is called on self.
public_send: Calls the given public method in self with the given argument.
#send: Calls the given method in self with the given argument.
to_s: Returns a string representation of self.

Constants

ARGF

ARGF is a stream designed for use in scripts that process files given as command-line arguments or passed in via STDIN.

See ARGF (the class) for more details.

ARGV

ARGV contains the command line arguments used to run ruby.

A library like OptionParser can be used to process command-line arguments.

BigDecimal::BASE

Base value used in internal calculations. On a 32 bit system, BASE is 10000, indicating that calculation is done in groups of 4 digits. (If it were larger, BASE**2 wouldn’t fit in 32 bits, so you couldn’t guarantee that two groups could always be multiplied together without overflow.)

BigDecimal::EXCEPTION_ALL

Determines whether overflow, underflow or zero divide result in an exception being thrown. See BigDecimal.mode.

BigDecimal::EXCEPTION_INFINITY

Determines what happens when the result of a computation is infinity. See BigDecimal.mode.

BigDecimal::EXCEPTION_NaN

Determines what happens when the result of a computation is not a number (NaN). See BigDecimal.mode.

BigDecimal::EXCEPTION_OVERFLOW

Determines what happens when the result of a computation is an overflow (a result too large to be represented). See BigDecimal.mode.

BigDecimal::EXCEPTION_UNDERFLOW

Determines what happens when the result of a computation is an underflow (a result too small to be represented). See BigDecimal.mode.

BigDecimal::EXCEPTION_ZERODIVIDE

Determines what happens when a division by zero is performed. See BigDecimal.mode.

BigDecimal::INFINITY

Special value constants

BigDecimal::NAN

BigDecimal::ROUND_CEILING

Round towards +Infinity. See BigDecimal.mode.

BigDecimal::ROUND_DOWN

Indicates that values should be rounded towards zero. See BigDecimal.mode.

BigDecimal::ROUND_FLOOR

Round towards -Infinity. See BigDecimal.mode.

BigDecimal::ROUND_HALF_DOWN

Indicates that digits >= 6 should be rounded up, others rounded down. See BigDecimal.mode.

BigDecimal::ROUND_HALF_EVEN

Round towards the even neighbor. See BigDecimal.mode.

BigDecimal::ROUND_HALF_UP

Indicates that digits >= 5 should be rounded up, others rounded down. See BigDecimal.mode.

BigDecimal::ROUND_MODE

Determines what happens when a result must be rounded in order to fit in the appropriate number of significant digits. See BigDecimal.mode.

BigDecimal::ROUND_UP

Indicates that values should be rounded away from zero. See BigDecimal.mode.

BigDecimal::SIGN_NEGATIVE_FINITE

Indicates that a value is negative and finite. See BigDecimal.sign.

BigDecimal::SIGN_NEGATIVE_INFINITE

Indicates that a value is negative and infinite. See BigDecimal.sign.

BigDecimal::SIGN_NEGATIVE_ZERO

Indicates that a value is -0. See BigDecimal.sign.

BigDecimal::SIGN_NaN

Indicates that a value is not a number. See BigDecimal.sign.

BigDecimal::SIGN_POSITIVE_FINITE

Indicates that a value is positive and finite. See BigDecimal.sign.

BigDecimal::SIGN_POSITIVE_INFINITE

Indicates that a value is positive and infinite. See BigDecimal.sign.

BigDecimal::SIGN_POSITIVE_ZERO

Indicates that a value is +0. See BigDecimal.sign.

BigDecimal::VERSION

The version of bigdecimal library

CROSS_COMPILING

CSV::DEFAULT_OPTIONS

Default values for method options.

CSV::VERSION

The version of the installed library.

Complex::I

Equivalent to Complex.rect(0, 1):

Complex::I # => (0+1i)

DATA

DATA is a File that contains the data section of the executed file. To create a data section use __END__:

$ cat t.rb
puts DATA.gets
__END__
hello world!

$ ruby t.rb
hello world!

DBM::NEWDB

Indicates that dbm_open() should open the database in read/write mode, create it if it does not already exist, and delete all contents if it does already exist.

DBM::READER

Indicates that dbm_open() should open the database in read-only mode

DBM::VERSION

Identifies ndbm library version.

Examples:

“ndbm (4.3BSD)”
“Berkeley DB 4.8.30: (April 9, 2010)”
“Berkeley DB (unknown)” (4.4BSD, maybe)
“GDBM version 1.8.3. 10/15/2002 (built Jul 1 2011 12:32:45)”
“QDBM 1.8.78”

DBM::WRCREAT

Indicates that dbm_open() should open the database in read/write mode, and create it if it does not already exist

DBM::WRITER

Indicates that dbm_open() should open the database in read/write mode

Date::ABBR_DAYNAMES

An array of strings of abbreviated day names in English. The first is “Sun”.

Date::ABBR_MONTHNAMES

An array of strings of abbreviated month names in English. The first element is nil.

Date::DAYNAMES

An array of strings of the full names of days of the week in English. The first is “Sunday”.

Date::ENGLAND

The Julian day number of the day of calendar reform for England and her colonies.

Date::GREGORIAN

The Julian day number of the day of calendar reform for the proleptic Gregorian calendar.

Date::ITALY

The Julian day number of the day of calendar reform for Italy and some catholic countries.

Date::JULIAN

The Julian day number of the day of calendar reform for the proleptic Julian calendar.

Date::MONTHNAMES

An array of strings of full month names in English. The first element is nil.

Digest::REQUIRE_MUTEX

A mutex for Digest().

ENV

ENV is a Hash-like accessor for environment variables.

See ENV (the class) for more details.

Encoding::Converter::AFTER_OUTPUT

Stop converting after some output is complete but before all of the input was consumed. See primitive_convert for an example.

Encoding::Converter::CRLF_NEWLINE_DECORATOR

Decorator for converting LF to CRLF

Encoding::Converter::CR_NEWLINE_DECORATOR

Decorator for converting LF to CR

Encoding::Converter::INVALID_MASK

Mask for invalid byte sequences

Encoding::Converter::INVALID_REPLACE

Replace invalid byte sequences

Encoding::Converter::PARTIAL_INPUT

Indicates the source may be part of a larger string. See primitive_convert for an example.

Encoding::Converter::UNDEF_HEX_CHARREF

Replace byte sequences that are undefined in the destination encoding with an XML hexadecimal character reference. This is valid for XML conversion.

Encoding::Converter::UNDEF_MASK

Mask for a valid character in the source encoding but no related character(s) in destination encoding.

Encoding::Converter::UNDEF_REPLACE

Replace byte sequences that are undefined in the destination encoding.

Encoding::Converter::UNIVERSAL_NEWLINE_DECORATOR

Decorator for converting CRLF and CR to LF

Encoding::Converter::XML_ATTR_CONTENT_DECORATOR

Escape as XML AttValue

Encoding::Converter::XML_ATTR_QUOTE_DECORATOR

Escape as XML AttValue

Encoding::Converter::XML_TEXT_DECORATOR

Escape as XML CharData

Float::DIG

The minimum number of significant decimal digits in a double-precision floating point.

Usually defaults to 15.

Float::EPSILON

The difference between 1 and the smallest double-precision floating point number greater than 1.

Usually defaults to 2.2204460492503131e-16.

Float::INFINITY

An expression representing positive infinity.

Float::MANT_DIG

The number of base digits for the double data type.

Usually defaults to 53.

Float::MAX

The largest possible integer in a double-precision floating point number.

Usually defaults to 1.7976931348623157e+308.

Float::MAX_10_EXP

The largest positive exponent in a double-precision floating point where 10 raised to this power minus 1.

Usually defaults to 308.

Float::MAX_EXP

The largest possible exponent value in a double-precision floating point.

Usually defaults to 1024.

Float::MIN

The smallest positive normalized number in a double-precision floating point.

Usually defaults to 2.2250738585072014e-308.

If the platform supports denormalized numbers, there are numbers between zero and Float::MIN. 0.0.next_float returns the smallest positive floating point number including denormalized numbers.

Float::MIN_10_EXP

The smallest negative exponent in a double-precision floating point where 10 raised to this power minus 1.

Usually defaults to -307.

Float::MIN_EXP

The smallest possible exponent value in a double-precision floating point.

Usually defaults to -1021.

Float::NAN

An expression representing a value which is “not a number”.

Float::RADIX

The base of the floating point, or number of unique digits used to represent the number.

Usually defaults to 2 on most systems, which would represent a base-10 decimal.

IO::APPEND

IO::BINARY

IO::CREAT

IO::DIRECT

IO::DSYNC

IO::EAGAINWaitReadable::Errno

IO::EAGAINWaitWritable::Errno

IO::EINPROGRESSWaitReadable::Errno

IO::EINPROGRESSWaitWritable::Errno

IO::EXCL

IO::FNM_CASEFOLD

IO::FNM_DOTMATCH

IO::FNM_EXTGLOB

IO::FNM_NOESCAPE

IO::FNM_PATHNAME

IO::FNM_SHORTNAME

IO::FNM_SYSCASE

IO::LOCK_EX

IO::LOCK_NB

IO::LOCK_SH

IO::LOCK_UN

IO::NOATIME

IO::NOCTTY

IO::NOFOLLOW

IO::NONBLOCK

IO::NULL

IO::PRIORITY

Priority event mask for IO#wait.

IO::RDONLY

IO::RDWR

IO::READABLE

Readable event mask for IO#wait.

IO::RSYNC

IO::SEEK_CUR

Set I/O position from the current position

IO::SEEK_DATA

Set I/O position to the next location containing data

IO::SEEK_END

Set I/O position from the end

IO::SEEK_HOLE

Set I/O position to the next hole

IO::SEEK_SET

Set I/O position from the beginning

IO::SHARE_DELETE

IO::SYNC

IO::TMPFILE

IO::TRUNC

IO::WRITABLE

Writable event mask for IO#wait.

IO::WRONLY

IPAddr::IN4MASK

32 bit mask for IPv4

IPAddr::IN6FORMAT

Format string for IPv6

IPAddr::IN6MASK

128 bit mask for IPv6

IPAddr::RE_IPV4ADDRLIKE

Regexp internally used for parsing IPv4 address.

IPAddr::RE_IPV6ADDRLIKE_COMPRESSED

Regexp internally used for parsing IPv6 address.

IPAddr::RE_IPV6ADDRLIKE_FULL

Regexp internally used for parsing IPv6 address.

JSON::FAST_STATE_PROTOTYPE

JSON::Infinity

JSON::JSON_LOADED

JSON::MinusInfinity

JSON::NaN

JSON::PRETTY_STATE_PROTOTYPE

JSON::SAFE_STATE_PROTOTYPE

JSON::VERSION

JSON::VERSION_ARRAY

JSON::VERSION_BUILD

JSON::VERSION_MAJOR

JSON::VERSION_MINOR

Logger::Formatter::Format

Logger::ProgName

Logger::SEV_LABEL

Severity label for logging (max 5 chars).

Logger::VERSION

Mutex_m::VERSION

NKF::ASCII

NKF::AUTO

NKF::BINARY

NKF::EUC

NKF::JIS

NKF::NKF_RELEASE_DATE

Release date of nkf

NKF::NKF_VERSION

Version of nkf

NKF::NOCONV

NKF::SJIS

NKF::UNKNOWN

NKF::UTF16

NKF::UTF32

NKF::UTF8

NKF::VERSION

Full version string of nkf

OptionParser::Acceptables::DecimalInteger

OptionParser::Acceptables::DecimalNumeric

OptionParser::Acceptables::OctalInteger

OptionParser::AmbiguousArgument::Reason

OptionParser::AmbiguousOption::Reason

OptionParser::ArgumentStyle

OptionParser::COMPSYS_HEADER

OptionParser::DecimalInteger

Decimal integer format, to be converted to Integer.

OptionParser::DecimalNumeric

Decimal integer/float number format, to be converted to Integer for integer format, Float for float format.

OptionParser::DefaultList

OptionParser::InvalidArgument::Reason

OptionParser::InvalidOption::Reason

OptionParser::MissingArgument::Reason

OptionParser::NO_ARGUMENT

OptionParser::NeedlessArgument::Reason

OptionParser::NoArgument

OptionParser::OPTIONAL_ARGUMENT

OptionParser::OctalInteger

Ruby/C like octal/hexadecimal/binary integer format, to be converted to Integer.

OptionParser::Officious

OptionParser::OptionalArgument

OptionParser::ParseError::Reason

Reason which caused the error.

OptionParser::REQUIRED_ARGUMENT

OptionParser::RequiredArgument

OptionParser::SPLAT_PROC

OptionParser::Version

An alias for compatibility

PM_ERROR_LEVEL_ARGUMENT

PM_ERROR_LEVEL_LOAD

PM_ERROR_LEVEL_SYNTAX

PM_WARNING_LEVEL_DEFAULT

PM_WARNING_LEVEL_VERBOSE

Process::CLOCK_BOOTTIME

see Process.clock_gettime

Process::CLOCK_BOOTTIME_ALARM

see Process.clock_gettime

Process::CLOCK_MONOTONIC

see Process.clock_gettime

Process::CLOCK_MONOTONIC_COARSE

see Process.clock_gettime

Process::CLOCK_MONOTONIC_RAW

see Process.clock_gettime

Process::CLOCK_PROCESS_CPUTIME_ID

see Process.clock_gettime

Process::CLOCK_REALTIME

see Process.clock_gettime

Process::CLOCK_REALTIME_ALARM

see Process.clock_gettime

Process::CLOCK_REALTIME_COARSE

see Process.clock_gettime

Process::CLOCK_THREAD_CPUTIME_ID

see Process.clock_gettime

Process::PRIO_PGRP

see Process.setpriority

Process::PRIO_PROCESS

see Process.setpriority

Process::PRIO_USER

see Process.setpriority

Process::RLIMIT_AS

Maximum size of the process’s virtual memory (address space) in bytes.