Ruby Pocket Reference

Global Constants

Table 5 describes all of Ruby’s global constants.

Table 5. Global constants

Constant	Description
ARGF	I/O-like stream that allows access to a virtual concatenation of all files provided on the command line, or standard input if no files are provided. Synonym for $<.
ARGV	Array that contains all the command-line arguments passed to a program. Synonym for $*.
DATA	An input stream for reading the lines of code following the _ _END_ _ directive. Not defined if _ _END_ _ is not present in code.
ENV	A hash-like object containing the program’s environment variables; can be treated as a hash.
FALSE	Synonym for false; false is preferred.
NIL	Synonym for nil; nil is preferred.
PLATFORM	Synonym for RUBY_PLATFORM. Deprecated.
RELEASE_DATE	Synonym for RUBY_RELEASE_DATE. Deprecated.
RUBY_PLATFORM	A string indicating the platform of the Ruby interpreter; e.g., “powerpc-darwin8.9.0.”
RUBY_RELEASE_DATE	A string indicating the release date of the Ruby interpreter; e.g., “2007-03-13.”
RUBY_VERSION	The Ruby version; e.g., “1.8.6.”
STDERR	Standard error output stream with default value of $stderr.
STDIN	Standard input stream with default value of $stdin.
STDOUT	Standard output stream with default value of $stdout.
TOPLEVEL_BINDING	A Binding object at Ruby’s top level.
TRUE	Synonym for true; true is preferred.
VERSION	Synonym for RUBY_VERSION. Deprecated.