Ruby in a Nutshell

Predefined Global Constants

TRUE, FALSE, and NIL are backward-compatible. It’s preferable to use true, false, and nil.

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, e.g., i686-linux.

RUBY_RELEASE_DATE

A string indicating the release date of the Ruby interpreter, e.g., 2001-09-19.

RUBY_VERSION

A string indicating the version of the Ruby interpreter, e.g., 1.6.5.

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.