Ruby/Language Basics/Global Constants

Constant            Description
ARGF                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. 
                    Synonym for $*.
DATA                Input stream for reading the lines of code following the _ _END_ _ directive. 
                    Not defined if _ _END_ _ is not present in code.
ENV                 Hash-like object containing the program"s environment variables; can be treated as a hash.
FALSE               Synonym for false.
NIL                 Synonym for nil; 
PLATFORM            Synonym for RUBY_PLATFORM. 
                    Deprecated.
RELEASE_DATE        Synonym for RUBY_RELEASE_DATE. Deprecated.
RUBY_PLATFORM   
RUBY_RELEASE_DATE   release date of the Ruby interpreter; e.g., "2006-08-25".
RUBY_VERSION        The Ruby version; e.g., "1.8.5".
STDERR              error output stream with default value of $stderr.
STDIN               input stream with default value of $stdin.
STDOUT              output stream with default value of $stdout.
TOPLEVEL_BINDING    Binding object at Ruby"s top level.
TRUE                Synonym for true; true is preferred.
VERSION             Synonym for RUBY_VERSION. Deprecated.