Kernel

RubyGems adds the gem method to allow activation of specific gem versions and overrides the require method on Kernel to make gems appear as if they live on the $LOAD_PATH. See the documentation of these methods for further detail.

The Kernel module is included by class Object, so its methods are available in every Ruby object.

The Kernel instance methods are documented in class Object while the module methods are documented here. These methods are called without a receiver and thus can be called in functional form:

sprintf "%.1f", 1.234 #=> "1.2"

What’s Here

Module Kernel provides methods that are useful for:

• Converting

• Querying

• Exiting

• Exceptions

• IO

• Procs

• Tracing

• Subprocesses

• Loading

• Yielding

• Random Values

• Other

Converting

• #Array

  Returns an Array based on the given argument.

• #Complex

  Returns a Complex based on the given arguments.

• #Float

  Returns a Float based on the given arguments.

• #Hash

  Returns a Hash based on the given argument.

• #Integer

  Returns an Integer based on the given arguments.

• #Rational

  Returns a Rational based on the given arguments.

• #String

  Returns a String based on the given argument.

Querying

• #__callee__

  Returns the called name of the current method as a symbol.

• #__dir__

  Returns the path to the directory from which the current method is called.

• #__method__

  Returns the name of the current method as a symbol.

• autoload?

  Returns the file to be loaded when the given module is referenced.

• binding

  Returns a Binding for the context at the point of call.

• block_given?

  Returns true if a block was passed to the calling method.

• caller

  Returns the current execution stack as an array of strings.

• caller_locations

  Returns the current execution stack as an array of Thread::Backtrace::Location objects.

• class

  Returns the class of self.

• frozen?

  Returns whether self is frozen.

• global_variables

  Returns an array of global variables as symbols.

• local_variables

  Returns an array of local variables as symbols.

• test

  Performs specified tests on the given single file or pair of files.

Exiting

• abort

  Exits the current process after printing the given arguments.

• at_exit

  Executes the given block when the process exits.

• exit

  Exits the current process after calling any registered at_exit handlers.

• exit!

  Exits the current process without calling any registered at_exit handlers.

Exceptions

• catch

  Executes the given block, possibly catching a thrown object.

• raise (aliased as fail)

  Raises an exception based on the given arguments.

• throw

  Returns from the active catch block waiting for the given tag.

IO

• gets

  Returns and assigns to $_ the next line from the current input.

• open

  Creates an IO object connected to the given stream, file, or subprocess.

• p

  Prints the given objects’ inspect output to the standard output.

• pp

  Prints the given objects in pretty form.

• print

  Prints the given objects to standard output without a newline.

• printf

  Prints the string resulting from applying the given format string to any additional arguments.

• putc

  Equivalent to <tt.$stdout.putc(object)</tt> for the given object.

• puts

  Equivalent to $stdout.puts(*objects) for the given objects.

• readline

  Similar to gets, but raises an exception at the end of file.

• readlines

  Returns an array of the remaining lines from the current input.

• select

  Same as IO.select.

Procs

• lambda

  Returns a lambda proc for the given block.

• proc

  Returns a new Proc; equivalent to Proc.new.

Tracing

• set_trace_func

  Sets the given proc as the handler for tracing, or disables tracing if given nil.

• trace_var

  Starts tracing assignments to the given global variable.

• untrace_var

  Disables tracing of assignments to the given global variable.

Subprocesses

• #cmd

  Returns the standard output of running cmd in a subshell.

• exec

  Replaces current process with a new process.

• fork

  Forks the current process into two processes.

• spawn

  Executes the given command and returns its pid without waiting for completion.

• system

  Executes the given command in a subshell.

Loading

• autoload

  Registers the given file to be loaded when the given constant is first referenced.

• load

  Loads the given Ruby file.

• require

  Loads the given Ruby file unless it has already been loaded.

• require_relative

  Loads the Ruby file path relative to the calling file, unless it has already been loaded.

Yielding

• tap

  Yields self to the given block; returns self.

• then (aliased as yield_self)

  Yields self to the block and returns the result of the block.

Random Values

• rand

  Returns a pseudo-random floating point number strictly between 0.0 and 1.0.

• srand

  Seeds the pseudo-random number generator with the given number.

Other

• eval

  Evaluates the given string as Ruby code.

• loop

  Repeatedly executes the given block.

• sleep

  Suspends the current thread for the given number of seconds.

• sprintf (aliased as format)

  Returns the string resulting from applying the given format string to any additional arguments.

• syscall

  Runs an operating system call.

• trap

  Specifies the handling of system signals.

• warn

  Issue a warning based on the given messages and options.