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.

Constant NameDescription
TRUESynonym for true.
FALSESynonym for false.
NILSynonym for nil.
ARGFAn 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 $<.
ARGVAn array containing the command-line arguments passed to the program. A synonym for $*.
DATAAn input stream for reading the lines of code following the __END__ directive. Not defined if __END__ isn't present in code.
ENVA hash-like object containing the program's environment variables. ENV can be handled as a hash.
RUBY_PLATFORMA string indicating the platform of the Ruby interpreter.
RUBY_RELEASE_DATEA string indicating the release date of the Ruby interpreter
RUBY_VERSIONA string indicating the version of the Ruby interpreter.
STDERRStandard error output stream. Default value of $stderr.
STDINStandard input stream. Default value of $stdin.
STDOUTStandard output stream. Default value of $stdout.
TOPLEVEL_BINDINGA binding object at Ruby's top level.