TRUE

Synonym for true.

FALSE

Synonym for false.

NIL

Synonym for nil.

ARGF

An object providing access to virtual concatenation of files passed as command-line arguments or standard input if there are no command-line arguments. A synonym for $<.

ARGV

An array containing the command-line arguments passed to the program. A synonym for $*.

DATA

An input stream for reading the lines of code following the __END__ directive. Not defined if __END__ isn’t present in code.

ENV

A hash-like object containing the program’s environment variables. ENV can be handled as a hash.

RUBY_PLATFORM

A string indicating the platform of the Ruby interpreter.

RUBY_RELEASE_DATE

A string indicating the release date of the Ruby interpreter

RUBY_VERSION

A string indicating the version of the Ruby interpreter.

STDERR

Standard error output stream. Default value of $stderr.

STDIN

Standard input stream. Default value of $stdin.

STDOUT

Standard output stream. Default value of $stdout.

TOPLEVEL_BINDING

A binding object at Ruby’s top level.