| Variable Name | Description |
| $! | 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. |
