Appendix A: Kernel methods list
- callcc: Generates a Continuation object, which it passes to the associated block.
- eval: Evaluates the Ruby expression(s) in string.
- lambda: Equivalent to Proc.new, except the resulting Proc objects check the number of parameters passed when called.
- proc: Equivalent to Proc.new.
- rand: If called without an argument, or if
max.to_i.abs == 0, rand returns a pseudo-random floating point number between 0.0 and 1.0, including 0.0 and excluding 1.0.
- srand: Seeds the system pseudo-random number generator, Random::DEFAULT, with
- warn: If warnings have been disabled (for example with the
-W0 flag), does nothing.
- autoload: Registers filename to be loaded (using Kernel::require) the first time that module (which may be a String or a symbol) is accessed.
- autoload?: Returns filename to be loaded if name is registered as
- load: Loads and executes the Ruby program in the file filename.
- require: Loads the given
true if successful and
false if the feature is already loaded.
- require_relative: Ruby tries to load the library named string relative to the requiring file’s path.
- gem (defined by RubyGems): Use
#gem to activate a specific version of gem_name.
- Array: Returns
arg as an Array.
- Complex: Returns
- Float: Returns arg converted to a float.
- Hash: Converts arg to a Hash by calling arg
- Integer: Converts arg to an Integer.
- Rational: Returns
arg as a Rational.
- String: Returns arg as a String.
- __callee__: Returns the called name of the current method as a Symbol.
- __dir__: Returns the canonicalized absolute path of the directory of the file from which this method is called.
- __method__: Returns the name at the definition of the current method as a Symbol.
- binding: Returns a
Binding object, describing the variable and method bindings at the point of call.
- block_given?: Returns
yield would execute a block in the current context.
- caller: Returns the current execution stack—an array containing strings in the form
file:line: in 'method'.
- caller_locations: Returns the current execution stack—an array containing backtrace location objects.
- global_variables: Returns an array of the names of global variables.
- local_variables: Returns the names of the current local variables.
- at_exit: Converts block to a
Proc object (and therefore binds it at the point of call) and registers it for execution when the program exits.
- exit: Initiates the termination of the Ruby script by raising the SystemExit exception.
- exit!: Exits the process immediately.
catch executes its block.
- throw: Transfers control to the end of the active
catch block waiting for tag.
- fail: With no arguments, raises the exception in
$! or raises a RuntimeError if
- raise: With no arguments, raises the exception in
$! or raises a RuntimeError if
- loop: Repeatedly executes the block.
- sleep: Suspends the current thread for duration seconds (which may be any number, including a
Float with fractional seconds).
IO and Strings
- gets: Returns (and assigns to
$_) the next line from the list of files in
$*), or from standard input if no files are present on the command line.
- format: Returns the string resulting from applying format_string to any additional arguments.
- p: For each object, directly writes obj.
inspect followed by a newline to the program’s standard output.
- print: Prints each object in turn to
- printf: Equivalent to: io.write(sprintf(string, obj, …)) or $stdout.write(sprintf(string, obj, …))
- putc: Equivalent to: $stdout.putc(int) Refer to the documentation for IO#putc for important information regarding multi-byte characters.
- puts: Equivalent to $stdout.puts(obj, …)
- readline: Equivalent to Kernel::gets, except
EOFError at end of file.
- readlines: Returns an array containing the lines returned by calling
Kernel.gets(*sep*) until the end of file.
- sprintf: Returns the string resulting from applying format_string to any additional arguments.
- pp Pretty-printing (more detailed version of
- open: Creates an IO object connected to the given stream, file, or subprocess.
- select: Calls select(2) system call.
- test: Uses the character
cmd to perform various tests on
file1 (first table below) or on
file2 (second table).
- set_trace_func: Establishes proc as the handler for tracing, or disables tracing if the parameter is
- trace_var: Controls tracing of assignments to global variables.
- untrace_var: Removes tracing for the specified command on the given global variable and returns
Processes and Commands
- `: Returns the standard output of running cmd in a subshell.
- exec: Replaces the current process by running the given external command.
- fork: Creates a subprocess.
- spawn: spawn executes specified command and return its pid.
- syscall: Calls the operating system function identified by num and returns the result of the function or raises SystemCallError if it failed.
- system: Executes command… in a subshell.
- trap: Specifies the handling of signals.