= Pre-Defined Global Variables Some of the pre-defined global variables have synonyms that are available via module Engish. For each of those, the \English synonym is given. To use the module: require 'English' == Exceptions === $! (\Exception) Contains the Exception object set by Kernel#raise: begin raise RuntimeError.new('Boo!') rescue RuntimeError p $! end Output: # English - $ERROR_INFO === $@ (Backtrace) Same as $!.backtrace; returns an array of backtrace positions: begin raise RuntimeError.new('Boo!') rescue RuntimeError pp $@.take(4) end Output: ["(irb):338:in `'", "/snap/ruby/317/lib/ruby/3.2.0/irb/workspace.rb:119:in `eval'", "/snap/ruby/317/lib/ruby/3.2.0/irb/workspace.rb:119:in `evaluate'", "/snap/ruby/317/lib/ruby/3.2.0/irb/context.rb:502:in `evaluate'"] English - $ERROR_POSITION. == Pattern Matching These global variables store information about the most recent successful match in the current scope. For details and examples, see {Regexp Global Variables}[rdoc-ref:Regexp@Global+Variables]. === $~ (\MatchData) MatchData object created from the match; thread-local and frame-local. English - $LAST_MATCH_INFO. === $& (Matched Substring) The matched string. English - $MATCH. === $` (Pre-Match Substring) The string to the left of the match. English - $PREMATCH. === $' (Post-Match Substring) The string to the right of the match. English - $POSTMATCH. === $+ (Last Matched Group) The last group matched. English - $LAST_PAREN_MATCH. === $1, $2, \Etc. (Matched Group) For $_n_ the _nth_ group of the match. No \English. == Separators === $/ (Input Record Separator) An input record separator, initially newline. English - $INPUT_RECORD_SEPARATOR, $RS. Aliased as $-0. === $; (Input Field Separator) An input field separator, initially +nil+. English - $FIELD_SEPARATOR, $FS. Aliased as $-F. === $\\ (Output Record Separator) An output record separator, initially +nil+. English - $OUTPUT_RECORD_SEPARATOR, $ORS. == Streams === $stdin (Standard Input) The current standard input stream; initially: $stdin # => #> === $stdout (Standard Output) The current standard output stream; initially: $stdout # => #> === $stderr (Standard Error) The current standard error stream; initially: $stderr # => #> === $< (\ARGF or $stdin) Points to stream ARGF if not empty, else to stream $stdin; read-only. English - $DEFAULT_INPUT. === $> (Default Standard Output) An output stream, initially $stdout. English - $DEFAULT_OUTPUT === $. (Input Position) The input position (line number) in the most recently read stream. English - $INPUT_LINE_NUMBER, $NR === $_ (Last Read Line) The line (string) from the most recently read stream. English - $LAST_READ_LINE. == Processes === $0 Initially, contains the name of the script being executed; may be reassigned. === $* (\ARGV) Points to ARGV. English - $ARGV. === $$ (Process ID) The process ID of the current process. Same as Process.pid. English - $PROCESS_ID, $PID. === $? (Child Status) Initially +nil+, otherwise the Process::Status object created for the most-recently exited child process; thread-local. English - $CHILD_STATUS. === $LOAD_PATH (Load Path) Contains the array of paths to be searched by Kernel#load and Kernel#require. Singleton method $LOAD_PATH.resolve_feature_path(feature) returns: - [:rb, _path_], where +path+ is the path to the Ruby file to be loaded for the given +feature+. - [:so+ _path_], where +path+ is the path to the shared object file to be loaded for the given +feature+. - +nil+ if there is no such +feature+ and +path+. Examples: $LOAD_PATH.resolve_feature_path('timeout') # => [:rb, "/snap/ruby/317/lib/ruby/3.2.0/timeout.rb"] $LOAD_PATH.resolve_feature_path('date_core') # => [:so, "/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/date_core.so"] $LOAD_PATH.resolve_feature_path('foo') # => nil Aliased as $: and $-I. === $LOADED_FEATURES Contains an array of the paths to the loaded files: $LOADED_FEATURES.take(10) # => ["enumerator.so", "thread.rb", "fiber.so", "rational.so", "complex.so", "ruby2_keywords.rb", "/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/enc/encdb.so", "/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/enc/trans/transdb.so", "/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/rbconfig.rb", "/snap/ruby/317/lib/ruby/3.2.0/rubygems/compatibility.rb"] Aliased as $". == Debugging === $FILENAME The value returned by method ARGF.filename. === $DEBUG Initially +true+ if command-line option -d or --debug is given, otherwise initially +false+; may be set to either value in the running program. When +true+, prints each raised exception to $stderr. Aliased as $-d. === $VERBOSE Initially +true+ if command-line option -v or -w is given, otherwise initially +false+; may be set to either value, or to +nil+, in the running program. When +true+, enables Ruby warnings. When +nil+, disables warnings, including those from Kernel#warn. Aliased as $-v and $-w. == Other Variables === $-a Whether command-line option -a was given; read-only. === $-i Contains the extension given with command-line option -i, or +nil+ if none. An alias of ARGF.inplace_mode. === $-l Whether command-line option -l was set; read-only. === $-p Whether command-line option -p was given; read-only. == Deprecated === $= === $, = Pre-Defined Global Constants = Streams === STDIN The standard input stream (the default value for $stdin): STDIN # => #> === STDOUT The standard output stream (the default value for $stdout): STDOUT # => #> === STDERR The standard error stream (the default value for $stderr): STDERR # => #> == Environment === ENV A hash of the contains current environment variables names and values: ENV.take(5) # => [["COLORTERM", "truecolor"], ["DBUS_SESSION_BUS_ADDRESS", "unix:path=/run/user/1000/bus"], ["DESKTOP_SESSION", "ubuntu"], ["DISPLAY", ":0"], ["GDMSESSION", "ubuntu"]] === ARGF The virtual concatenation of the files given on the command line, or from $stdin if no files were given, "-" is given, or after all files have been read. === ARGV An array of the given command-line arguments. === TOPLEVEL_BINDING The Binding of the top level scope: TOPLEVEL_BINDING # => # === RUBY_VERSION The Ruby version: RUBY_VERSION # => "3.2.2" === RUBY_RELEASE_DATE The release date string: RUBY_RELEASE_DATE # => "2023-03-30" === RUBY_PLATFORM The platform identifier: RUBY_PLATFORM # => "x86_64-linux" === RUBY_PATCHLEVEL The integer patch level for this Ruby: RUBY_PATCHLEVEL # => 53 For a development build the patch level will be -1. === RUBY_REVISION The git commit hash for this Ruby: RUBY_REVISION # => "e51014f9c05aa65cbf203442d37fef7c12390015" === RUBY_COPYRIGHT The copyright string: RUBY_COPYRIGHT # => "ruby - Copyright (C) 1993-2023 Yukihiro Matsumoto" === RUBY_ENGINE The name of the Ruby implementation: RUBY_ENGINE # => "ruby" === RUBY_ENGINE_VERSION The version of the Ruby implementation: RUBY_ENGINE_VERSION # => "3.2.2" === RUBY_DESCRIPTION The description of the Ruby implementation: RUBY_DESCRIPTION # => "ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]" == Embedded \Data === DATA Defined if and only if the program has this line: __END__ When defined, DATA is a File object containing the lines following the __END__, positioned at the first of those lines: p DATA DATA.each_line { |line| p line } __END__ Foo Bar Baz Output: # "Foo\n" "Bar\n" "Baz\n"