$!

The last exception object raised. The exception object can also be accessed using => in rescue clause.

$@

The stack backtrace for the last exception raised. The stack backtrace information can retrieved by Exception#backtrace method of the last exception.

$/

The input record separator (newline by default). gets, readline, etc., take their input record separator as optional argument.

$\

The output record separator (nil by default).

$,

The output separator between the arguments to print and Array#join (nil by default). You can specify separator explicitly to Array#join.

$;

The default separator for split (nil by default). You can specify separator explicitly for String#split.

$.

The number of the last line read from the current input file. Equivalent to ARGF.lineno.

$<

Synonym for ARGF.

$>

Synonym for $defout.

$0

The name of the current Ruby program being executed.

$$

The process pid of the current Ruby program being executed.

$?

The exit status of the last process terminated.

$:

Synonym for $LOAD_PATH.

$DEBUG

True if the -d or –debug command-line option is specified.

$defout

The destination output for print and printf ($stdout by default).

$F

The variable that receives the output from split when -a is specified. This variable is set if the -a command-line option is specified along with the -p or -n option.

$FILENAME

The name of the file currently being read from ARGF. Equivalent to ARGF.filename.

$LOAD_PATH

An array holding the directories to be searched when loading files with the load and require methods.

$SAFE

The security level

0 → No checks are performed on externally supplied (tainted) data. (default)

1 → Potentially dangerous operations using tainted data are forbidden.

2 → Potentially dangerous operations on processes and files are forbidden.

3 → All newly created objects are considered tainted.

4 → Modification of global data is forbidden.

$stdin

Standard input (STDIN by default).

$stdout

Standard output (STDOUT by default).

$stderr

Standard error (STDERR by default).

$VERBOSE

True if the -v, -w, or –verbose command-line option is specified.

$- x

The value of interpreter option -x (x=0, a, d, F, i, K, l, p, v). These options are listed below

$-0

The value of interpreter option -x and alias of $/.

$-a

The value of interpreter option -x and true if option -a is set. Read-only.

$-d

The value of interpreter option -x and alias of $DEBUG

$-F

The value of interpreter option -x and alias of $;.

$-i

The value of interpreter option -x and in in-place-edit mode, holds the extension, otherwise nil. Can enable or disable in-place-edit mode.

$-I

The value of interpreter option -x and alias of $:.

$-l

The value of interpreter option -x and true if option -lis set. Read-only.

$-p

The value of interpreter option -x and true if option -pis set. Read-only.

$_

The local variable, last string read by gets or readline in the current scope.

$~

The local variable, MatchData relating to the last match. Regex#match method returns the last match information.

$ n ($1, $2, $3…)

The string matched in the nth group of the last pattern match. Equivalent to m[n], where m is a MatchData object.

$&

The string matched in the last pattern match. Equivalent to m[0], where m is a MatchData object.

$`

The string preceding the match in the last pattern match. Equivalent to m.pre_match, where m is a MatchData object.

$’

The string following the match in the last pattern match. Equivalent to m.post_match, where m is a MatchData object.

$+

The string corresponding to the last successfully matched group in the last pattern match.