Ruby - Predefined Constants

The following table lists all the Ruby's Predefined Constants −

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

Sr.No.	Constant Name & Description
1	TRUE Synonym for true.
2	FALSE Synonym for false.
3	NIL Synonym for nil.
4	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 $<.
5	ARGV An array containing the command-line arguments passed to the program. A synonym for $*.
6	DATA An input stream for reading the lines of code following the __END__ directive. Not defined if __END__ isn't present in code.
7	ENV A hash-like object containing the program's environment variables. ENV can be handled as a hash.
8	RUBY_PLATFORM A string indicating the platform of the Ruby interpreter.
9	RUBY_RELEASE_DATE A string indicating the release date of the Ruby interpreter
10	RUBY_VERSION A string indicating the version of the Ruby interpreter.
11	STDERR Standard error output stream. Default value of $stderr.
12	STDIN Standard input stream. Default value of $stdin.
13	STDOUT Standard output stream. Default value of $stdout.
14	TOPLEVEL_BINDING A binding object at Ruby's top level.