Top-level constants in Ruby

ARGF

An Io object that connects all the files specified in the argv into a file. If argv is empty, then it represents standard input. Synonyms $<

Argv

An array that contains all the parameters specified by the command line. Synonyms $*

DATA

Represents all text line flows after __end__, if no __end__, data is undefined

Env

An object that behaves like a hash object that can access the environment variables available in the Interpreter

Ruby_patchlevel

String indicating the patch number of the interpreter

Ruby_release_date

A string that indicates the date the Ruby interpreter was published

Ruby_version

Version number to indicate the Ruby language supported by the interpreter

STDERR

Standard error stream. is the default value for the $STDERR variable

Stdin

Standard input stream. is the default value for the $stdin variable

STDOUT

Standard output stream. is the default value for $stdout

Toplevel_binding

A binding object that represents the top-level scope of the binding

Top-level constants in Ruby