# -*- mode: rdoc; coding: utf-8; fill-column: 74; -*-

== Pre-defined variables

$!::   The exception information message set by 'raise'.
$@::   Array of backtrace of the last exception thrown.
$&::   The string matched by the last successful match.
$`::   The string to the left  of the last successful match.
$'::   The string to the right of the last successful match.
$+::   The highest group matched by the last successful match.
$1::   The Nth group of the last successful match. May be > 1.
$~::   The information about the last match in the current scope.
$=::   The flag for case insensitive, nil by default.
$/::   The input record separator, newline by default.
$\::   The output record separator for the print and IO#write. Default is nil.
$,::   The output field separator for the print and Array#join.
$;::   The default separator for String#split.
$.::   The current input line number of the last file that was read.
$<::   The virtual concatenation file of the files given on command line (or from $stdin if no files were given).
$>::   The default output for print, printf. $stdout by default.
$_::   The last input line of string by gets or readline.
$0::   Contains the name of the script being executed. May be assignable.
$*::   Command line arguments given for the script sans args.
$$::   The process number of the Ruby running this script.
$?::   The status of the last executed child process.  This value is
       thread-local.
$:::   Load path for scripts and binary modules by load or require.
$"::   The array contains the module names loaded by require.
$DEBUG::     The debug flag, which is set by the -d switch.  Enabling debug
             output prints each exception raised to $stderr (but not its
             backtrace).  Setting this to a true value enables debug output as
             if -d were given on the command line.  Setting this to a false
             value disables debug output.
$FILENAME::  Current input file from $<. Same as $<.filename.
$LOAD_PATH:: The alias to the $:.
$stderr::    The current standard error output.
$stdin::     The current standard input.
$stdout::    The current standard output.
$VERBOSE::   The verbose flag, which is set by the -w or -v switch.  Setting
             this to a true value enables warnings as if -w or -v were given
             on the command line.  Setting this to nil disables warnings,
             including from Kernel#warn.
$-0::  The alias to $/.
$-a::  True if option -a is set. Read-only variable.
$-d::  The alias of $DEBUG.  See $DEBUG above for further discusison.
$-F::  The alias to $;.
$-i::  In in-place-edit mode, this variable holds the extension, otherwise nil.
$-I::  The alias to $:.
$-l::  True if option -l is set. Read-only variable.
$-p::  True if option -p is set. Read-only variable.
$-v::  An alias of $VERBOSE.  See $VERBOSE above for further discussion.
$-w::  An alias of $VERBOSE.  See $VERBOSE above for further discussion.

== Pre-defined global constants

TRUE::              The typical true value.
FALSE::             The false itself.
NIL::               The nil itself.
STDIN::             The standard input. The default value for $stdin.
STDOUT::            The standard output. The default value for $stdout.
STDERR::            The standard error output. The default value for $stderr.
ENV::               The hash contains current environment variables.
ARGF::              The alias to the $<.
ARGV::              The alias to the $*.
DATA::              The file object of the script, pointing just after __END__.
RUBY_VERSION::      The ruby version string (VERSION was deprecated).
RUBY_RELEASE_DATE:: The release date string.
RUBY_PLATFORM::     The platform identifier.

