Yokerhood · Aleksei Matiushkin

Below is the summary table for the predefined globals in ruby.

<table class="table table-bordered code"> <tbody> <tr> <td><a href="#bang" class="btn">$!</a></td> <td><a href="#plus" class="btn">$+</a></td> <td><a href="#minus-w" class="btn">$-W</a></td> <td><a href="#minus-v-small" class="btn">$-v</a></td> <td><a href="#digit" class="btn">$2</a></td> <td><a href="#digit" class="btn">$8</a></td> <td><a href="#greater" class="btn">$></a></td> </tr> <tr> <td><a href="#double-quotes" class="btn">$"</a></td> <td><a href="#comma" class="btn">$,</a></td> <td><a href="#minus-a-small" class="btn">$-a</a></td> <td><a href="#minus-w-small" class="btn">$-w</a></td> <td><a href="#digit" class="btn">$3</a></td> <td><a href="#digit" class="btn">$9</a></td> <td><a href="#qmark" class="btn">$?</a></td> </tr> <tr> <td><a href="#dollar" class="btn">$$</a></td> <td><a href="#minus-zero" class="btn">$-0</a></td> <td><a href="#minus-d-small" class="btn">$-d</a></td> <td><a href="#dot" class="btn">$.</a></td> <td><a href="#digit" class="btn">$4</a></td> <td><a href="#colon" class="btn">$:</a></td> <td><a href="#at" class="btn">$ @ </tr> <tr> <td><a href="#ampersand" class="btn">$&</a></td> <td><a href="#minus-f" class="btn">$-F</a></td> <td><a href="#minus-i-small" class="btn">$-i</a></td> <td><a href="#slash" class="btn">$/</a></td> <td><a href="#digit" class="btn">$5</a></td> <td><a href="#semicolon" class="btn">$;</a></td> <td><a href="#backslash" class="btn">$</a></td> </tr> <tr> <td><a href="#end-quote" class="btn">$'</a></td> <td><a href="#minus-i" class="btn">$-I</a></td> <td><a href="#minus-l-small" class="btn">$-l</a></td> <td><a href="#digit" class="btn">$0</a></td> <td><a href="#digit" class="btn">$6</a></td> <td><a href="#less" class="btn">$<</a></td> <td><a href="#underscore" class="btn">$ </a></td> </tr> <tr> <td><a href="#splat" class="btn">$ </a></td> <td><a href="#minus-k" class="btn">$-K</a></td> <td><a href="#minus-p-small" class="btn">$-p</a></td> <td><a href="#digit" class="btn">$1</a></td> <td><a href="#digit" class="btn">$7</a></td> <td><a href="#tilde" class="btn">$ ~~</a></td> <td><a href="#backtick" class="btn">$~~

Variable Description $! Exception === $! unless $!.nil? read-only thread-local The last exception, that was thrown and rescued in the current context. Locals to the rescue clause. ruby > 0 / 0 rescue $! # ⇒ > begin > 0 / 0 > rescue > $! > end # ⇒ > 0 / 0 # ZeroDivisionError: divided by 0 # from (pry):67:in `/' > $! # ⇒ nil $" Array === $" read-only Array of strings, containing absolute paths to loaded files. Files, loaded within both Kernel’s load, require, require_relative directives and platform-specific DL/Fiddle, are shown in the list. ruby > $" # ⇒ [ # [ 0] "enumerator.so", # [ 1] "/…/lib/ruby/2.0.0/x86_64-linux/enc/encdb.so", # [ 2] "/…/lib/ruby/2.0.0/x86_64-linux/enc/trans/transdb.so", # [ 3] "/…/lib/ruby/site_ruby/2.0.0/rubygems/defaults.rb", # [ 4] "/…/lib/ruby/2.0.0/x86_64-linux/rbconfig.rb", # … # [227] "/…/lib/ruby/2.0.0/dl.rb" # ] $$ Fixnum === $$ read-only Current process ID. ruby > $" # ⇒ 8603 > Process.pid # ⇒ 8603 $& String === $& unless $&.nil? read-only thread-local The matched string from the previous successful pattern match. Locals to the pattern match scope. ruby > "foo bar baz".match /foo|bar|baz/ # ⇒ > $& # ⇒ "foo" > "foo bar baz".gsub /foo|bar|baz/, "ggg" # ⇒ "ggg ggg ggg" > $& # ⇒ "baz" > "foo bar baz".match /foobarbaz/ # ⇒ nil > $& # ⇒ nil $' String === $' unless $'.nil? read-only thread-local The rest of the string after the matched substring in the previous successful pattern match. Locals to the pattern match scope. ruby > "foo bar baz".match /foo|bar|baz/ # ⇒ > $' # ⇒ " bar baz" > "foo bar baz".gsub /foo|bar|baz/, 'ggg' # ⇒ "ggg ggg ggg" > $' # ⇒ "" > "foo bar baz".match /foobarbaz/ # ⇒ nil > $' # ⇒ nil $* Array === $* read-only The command line arguments passed to the currently executed ruby script. An alias for ARGV. ruby ~ pry --simple-prompt > $* # ⇒ [ # [0] "--simple-prompt" # ] > ARGV # ⇒ [ # [0] "--simple-prompt" # ] $+ String === $+ unless $+.nil? read-only thread-local The last captured match from the previous successful pattern match. Locals to the pattern match scope. Contains nil if there was no capture (even while match was successful.) ruby > "foo bar baz".match /(foo) (bar) baz/ # ⇒ > $+ # ⇒ "bar" > "foo bar baz".scan (/a(\S)/) { |m| puts m } # r # z # ⇒ "foo bar baz" > $+ # ⇒ "z" > "foo bar baz".match /foo bar baz/ # ⇒ > $+ # ⇒ nil $, String === $, unless $,.nil? read-write Separator for both Kernel#print and Array#join. Defaults to nil. ruby > print "foo", "bar", "baz" # foobarbaz⇒ nil > %w[foo bar baz].join # ⇒ "foobarbaz" > $,='%' # ⇒ "%" > print "foo", "bar", "baz" # foo%bar%baz⇒ nil > %w[foo bar baz].join # ⇒ "foo%bar%baz" $-0 $/ String === $-0 unless $-0.nil? String === $/ unless $/.nil? read-write Input record separator. Defaults to \n. May be set with the -0 command line parameter (as octal value.) ruby > $-0='%' # ⇒ "%" > gets f o o % # ⇒ "f\no\no\n%" ~ ruby -045 /…/bin/pry > gets f o o % # ⇒ "f\no\no\n%" > $-F $; String === $-F unless $-F.nil? String === $: unless $:.nil? read-write Default field separator for String#split. Defaults to nil. May be set with the -F command line parameter. ruby > $-F # ⇒ nil > "foo bar baz".split # ⇒ [ # [0] "foo", # [1] "bar", # [2] "baz" # ] > $-F='%' # ⇒ "%" > "foo bar baz".split # ⇒ [ # [0] "foo bar baz" # ] > "foo%bar%baz".split # ⇒ [ # [0] "foo", # [1] "bar", # [2] "baz" # ] > $-F == $; # ⇒ true $-I $: Array === $-I Array === $: read-only Array of include paths. Absolute paths to be searched by Kernel.load and/or Kernel.require. ruby > $-I # ⇒ [ # [ 0] "/…/gems/rubygems-bundler-1.1.0/lib", # [ 1] "/…/gems/bundler-1.2.3/lib", # [ 2] "/…/gems/coderay-1.0.8/lib", # [ 3] "/…/gems/slop-3.4.3/lib", # … # [14] "/…/lib/ruby/2.0.0/x86_64-linux" # ] > $-I == $: # ⇒ true $-K String === $-K unless $-K.nil? obsolete read-write Determines the encoding to be used whilst parsing .rb files. One should avoid using that variable since ruby-1.9. ruby > $-K # (pry):13: warning: variable $KCODE is no longer effective # ⇒ nil $-W Fixnum === $-W read-only Current verbosity level. Defaults to 1. May be set to 0 with the -W0 command line arg and to 2 with one of -w, -v, or --verbose switches. ruby > $-W # ⇒ 1 > exit ~ ruby -v /…/bin/pry # ruby 2.0.0dev (2012-12-01 trunk 38126) [x86_64-linux] # /…/gems/method_source-0.8.1/lib/method_source/code_helpers.rb:38: warning: assigned but unused variable - e2 # … # /…/gems/pry-0.9.11.4/lib/pry/pry_class.rb:446: warning: instance variable @critical_section not initialized > $-W # /…/gems/awesome_print-1.1.0/lib/awesome_print/inspector.rb:114: warning: instance variable @force_colors not initialized # ⇒ 2 > exit ~ ruby -W0 /…/bin/pry > $-W # ⇒ 0 > $-a ∈ [true, false] read-only Denotes whether the auto-split mode was enabled with -a command line argument. -a switch makes sense when used together with either -p or -n args. In auto-split mode, Ruby executes $F = $_.split at the beginning of each loop. ruby ~ cat > test-a-switch.rb 〈〈EOF # heredoc> # encoding: utf-8 # heredoc> puts "LINE=[#{\$_.strip}]" # heredoc> puts "\$F=#{\$F}" # heredoc> EOF ~ ruby -a -n test-a-switch.rb test-a-switch.rb # LINE=[# encoding: utf-8] # $F=["#", "encoding:", "utf-8"] # LINE=[puts "LINE=#{$_.strip}"] # $F=["puts", "\"LINE=\#{$_.strip},"] # LINE=[puts "$F=#{$F}"] # $F=["puts", "$F=\#{$F}\""] ~ ruby -n test-a-switch.rb test-a-switch.rb # LINE=# encoding: utf-8 # $F= # LINE=puts "LINE=#{$_.strip}" # $F= # LINE=puts "$F=#{$F}" # $F= $-d ∈ [true, false] read-only Denotes whether the debug mode was enabled with -d switch. ruby ~ cat > test-d-switch.rb 〈〈EOF # heredoc> puts "DEBUG MODE: #{\$-d}" # heredoc> EOF ~ ruby -d test-d-switch.rb # Exception `LoadError' at /…/lib/ruby/site_ruby/2.0.0/rubygems.rb:1264 - cannot load such file -- rubygems/defaults/operating_system # Exception `LoadError' at /…/lib/ruby/site_ruby/2.0.0/rubygems.rb:1273 - cannot load such file -- rubygems/defaults/ruby # DEBUG MODE: true $-i ∈ [true, false] read-only Value of the -i command line argument, if given. Defaults to nil. When provided, this argument enables inplace-edit mode; the parameter specifies an extension of backup file to be created. ruby ~ cat > test-i-switch.rb << EOF \$_.upcase! puts "i-switch: #{\$-i}" EOF ~ ruby -p -i.bak test-i-switch.rb test-i-switch.rb ~ cat test-i-switch.rb # i-switch: .bak # $_.UPCASE! # i-switch: .bak # PUTS "I-SWITCH: #{$-I}" $-l ∈ [true, false] read-only Denotes whether the automatic line-ending processing mode was enabled with -l switch. Automatic line-endings sets $\ to the value of $/, and (when used with either -p or -n args) chops every line read using chop!. ruby # Could not invent a meaningful example :-( $-p ∈ [true, false] read-only Denotes whether the “gets loop around” mode was enabled with -p switch. -p switch acts mostly like -n sibling with one exception: it prints the value of variable $_ at the each end of the loop. For some unknown reason there is no internal global to get aknowledged whether the -n command line switch was given. In case it were, Ruby is to assume the following loop around your script, which provides an iteration over filename arguments somewhat like sed -n and awk do. ruby while gets … end An example of usage follows: ruby ~ echo "foo bar baz" | ruby -p -e '$_.tr! "o-z", "O-Z"' # ⇒ fOO baR baZ $-v $-w ∈ [true, false] read-only Denotes whether the verbose mode was enabled with either -v or -w switch. ruby ~ cat > test-v-switch.rb 〈〈EOF # heredoc> puts "VERBOSE MODE: #{\$-v}" # heredoc> EOF ~ ruby -v test-v-switch.rb # ruby 2.0.0dev (2012-12-01 trunk 38126) [x86_64-linux] # VERBOSE MODE: true ~ $. Fixnum === $. read-only Number of the last line read from the current input file ARGF. ARGF is a stream designed to use in scripts that process files given as command-line arguments or passed in via STDIN. ruby ARGV.replace ["file1"] # file1 ≡ 'a\nb\nc\nd' ARGF.readlines # Returns the contents of file1 as an Array $. # ⇒ 4 $0…$9 String === $0 unless $0.nil? String === $1 unless $1.nil? String === $2 unless $2.nil? String === $3 unless $3.nil? String === $4 unless $4.nil? String === $5 unless $5.nil? String === $6 unless $6.nil? String === $7 unless $7.nil? String === $8 unless $8.nil? String === $9 unless $9.nil? read-only The N-th capture of the previous successful pattern match. Defaults to nil if the match failed or if N is greater than an amount of captured groups. ruby > "foo bar baz".match(/(foo) (bar)/) # ⇒ > $1 # ⇒ "foo" > $2 # ⇒ "bar" > $3 # ⇒ nil $< ARGF === $< read-only Read‐only alias for ARGF. ruby > $<.class # ⇒ ARGF.class < Object $= ∈ [true, false] obsolete ruby > $= # (pry):23: warning: variable $= is no longer effective # ⇒ false $> IO === $> read-write Standard output stream. ruby > $> = File.new('/tmp/foo', 'w') # ⇒ # -rw-r--r-- 1 am users 0 Feb 27 12:41 /tmp/foo > puts "bar baz" # ⇒ nil > exit ~ cat /tmp/foo # bar baz $? Process::Status === $? unless $?.nil? read-only Exit status of the last terminated process within current context. ruby > `ls FooBarBaz` # ls: невозможно получить доступ к FooBarBaz: Нет такого файла или каталога # ⇒ "" > $? # ⇒ $@ Array === $@ unless $@.nil? read-only thread-local Shorthand to $!.backtrace Locals to the rescue clause. ruby > 0 / 0 rescue $@ # ⇒ [ # [ 0] "(pry):7:in `/'", # [ 1] "(pry):7:in `__pry__'", # … # [23] "/…/bin/ruby_noexec_wrapper:14:in `'" # ] $\ String === $\ unless $\.nil? read-write Appended to Kernel.print output. Defaults to nil, or to $/ if the -l switch was given. ruby > $\='%' # ⇒ "%" > print 'foo', 'bar', 'baz' # ⇒ %foobarbaz%=> nil $_ String === $_ unless $_.nil? read-only thread-local Last String read from IO by one of Kernel.gets, Kernel.readline or siblings. Widely used with -p and -n switches. ruby > gets foo # ⇒ "foo\n" > $_ # ⇒ "foo\n" $ </code> String === $ unless $ .nil? </td> <td> read-only thread-local The rest of the string before the matched substring in the previous successful pattern match. Locals to the pattern match scope. > "foo bar baz".match /bar|baz/ # ⇒ <MatchData "bar"> > $` # ⇒ "foo " > "foo bar baz".gsub /foo|bar|baz/, 'ggg' # ⇒ "ggg ggg ggg" > $` # ⇒ "foo bar " > "foo bar baz".match /foobarbaz/ # ⇒ nil > $` # ⇒ nil </td> </tr> <tr> <td class="tooltipable"> <a id="tilde"></a> <code class="btn btn-large disabled">$ </code> MatchData === $ unless $ .nil? </td> <td> read-only thread-local The <code>MatchData</code> from the previous successful pattern match. > "abc12def34ghijklmno567pqrs".gsub (/\d+/) { |m| p $~ } # ⇒ <MatchData "12"> # ⇒ <MatchData "34"> # ⇒ <MatchData "567"> </td> </tr> </tbody> </table> </div> Credits to Jim Neath and runpaint , some examples came from these posts. ← Ruby Blocks: Do-end vs. Braces Ruby Shorthand to Yield Within Blocks → Uses Now CV Projects © 2026 Aleksei Matiushkin · Keyboard shortcuts g h Go home g b Go to the blog g p Go to projects g m Go to the maze j / k Move through the current list n / p Next / previous post or project / Focus search t Cycle theme ? 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Variable	Description
`$!` Exception === $! unless $!.nil?	read-only thread-local *The last exception, that was thrown and rescued* in the current context.** Locals to the `rescue` clause. ruby > 0 / 0 rescue $! # ⇒ > begin > 0 / 0 > rescue > $! > end # ⇒ > 0 / 0 # ZeroDivisionError: divided by 0 # from (pry):67:in `/' > $! # ⇒ nil
`$"` Array === $"	read-only Array of strings, containing absolute paths to loaded files. Files, loaded within both `Kernel’s` `load`, `require`, `require_relative` directives *and* platform-specific DL/Fiddle, are shown in the list. ruby > $" # ⇒ [ # [ 0] "enumerator.so", # [ 1] "/…/lib/ruby/2.0.0/x86_64-linux/enc/encdb.so", # [ 2] "/…/lib/ruby/2.0.0/x86_64-linux/enc/trans/transdb.so", # [ 3] "/…/lib/ruby/site_ruby/2.0.0/rubygems/defaults.rb", # [ 4] "/…/lib/ruby/2.0.0/x86_64-linux/rbconfig.rb", # … # [227] "/…/lib/ruby/2.0.0/dl.rb" # ]
`$$` Fixnum === $$	read-only Current process ID. ruby > $" # ⇒ 8603 > Process.pid # ⇒ 8603
`$&` String === $& unless $&.nil?	read-only thread-local The matched string from the previous successful pattern match. Locals to the pattern match scope. ruby > "foo bar baz".match /foo\|bar\|baz/ # ⇒ > $& # ⇒ "foo" > "foo bar baz".gsub /foo\|bar\|baz/, "ggg" # ⇒ "ggg ggg ggg" > $& # ⇒ "baz" > "foo bar baz".match /foobarbaz/ # ⇒ nil > $& # ⇒ nil
`$'` String === $' unless $'.nil?	read-only thread-local *The rest of the string after the matched* substring in the previous successful pattern match.** Locals to the pattern match scope. ruby > "foo bar baz".match /foo\|bar\|baz/ # ⇒ > $' # ⇒ " bar baz" > "foo bar baz".gsub /foo\|bar\|baz/, 'ggg' # ⇒ "ggg ggg ggg" > $' # ⇒ "" > "foo bar baz".match /foobarbaz/ # ⇒ nil > $' # ⇒ nil
`$` Array === $	read-only The command line arguments passed to the currently executed ruby script. An alias for `ARGV`. ruby ~ pry --simple-prompt > $* # ⇒ [ # [0] "--simple-prompt" # ] > ARGV # ⇒ [ # [0] "--simple-prompt" # ]
`$+` String === $+ unless $+.nil?	read-only thread-local *The last captured* match from the previous successful pattern match.** Locals to the pattern match scope. Contains `nil` if there was no capture (even while match was successful.) ruby > "foo bar baz".match /(foo) (bar) baz/ # ⇒ > $+ # ⇒ "bar" > "foo bar baz".scan (/a(\S)/) { \|m\| puts m } # r # z # ⇒ "foo bar baz" > $+ # ⇒ "z" > "foo bar baz".match /foo bar baz/ # ⇒ > $+ # ⇒ nil
`$,` String === $, unless $,.nil?	read-write Separator for both `Kernel#print` and `Array#join`. Defaults to nil. ruby > print "foo", "bar", "baz" # foobarbaz⇒ nil > %w[foo bar baz].join # ⇒ "foobarbaz" > $,='%' # ⇒ "%" > print "foo", "bar", "baz" # foo%bar%baz⇒ nil > %w[foo bar baz].join # ⇒ "foo%bar%baz"
`$-0` `$/` String === $-0 unless $-0.nil? String === $/ unless $/.nil?	read-write Input record separator. Defaults to `\n`. May be set with the `-0` command line parameter (as octal value.) ruby > $-0='%' # ⇒ "%" > gets f o o % # ⇒ "f\no\no\n%" ~ ruby -045 /…/bin/pry > gets f o o % # ⇒ "f\no\no\n%" >
`$-F` `$;` String === $-F unless $-F.nil? String === $: unless $:.nil?	read-write Default field separator for `String#split`. Defaults to `nil`. May be set with the `-F` command line parameter. ruby > $-F # ⇒ nil > "foo bar baz".split # ⇒ [ # [0] "foo", # [1] "bar", # [2] "baz" # ] > $-F='%' # ⇒ "%" > "foo bar baz".split # ⇒ [ # [0] "foo bar baz" # ] > "foo%bar%baz".split # ⇒ [ # [0] "foo", # [1] "bar", # [2] "baz" # ] > $-F == $; # ⇒ true
`$-I` `$:` Array === $-I Array === $:	read-only Array of include paths. Absolute paths to be searched by `Kernel.load` and/or `Kernel.require`. ruby > $-I # ⇒ [ # [ 0] "/…/gems/rubygems-bundler-1.1.0/lib", # [ 1] "/…/gems/bundler-1.2.3/lib", # [ 2] "/…/gems/coderay-1.0.8/lib", # [ 3] "/…/gems/slop-3.4.3/lib", # … # [14] "/…/lib/ruby/2.0.0/x86_64-linux" # ] > $-I == $: # ⇒ true
`$-K` String === $-K unless $-K.nil?	obsolete read-write Determines the encoding to be used whilst parsing `.rb` files. One should avoid using that variable since `ruby-1.9`. ruby > $-K # (pry):13: warning: variable $KCODE is no longer effective # ⇒ nil
`$-W` Fixnum === $-W	read-only Current verbosity level. Defaults to `1`. May be set to `0` with the `-W0` command line arg and to `2` with one of `-w`, `-v`, or `--verbose` switches. ruby > $-W # ⇒ 1 > exit ~ ruby -v /…/bin/pry # ruby 2.0.0dev (2012-12-01 trunk 38126) [x86_64-linux] # /…/gems/method_source-0.8.1/lib/method_source/code_helpers.rb:38: warning: assigned but unused variable - e2 # … # /…/gems/pry-0.9.11.4/lib/pry/pry_class.rb:446: warning: instance variable @critical_section not initialized > $-W # /…/gems/awesome_print-1.1.0/lib/awesome_print/inspector.rb:114: warning: instance variable @force_colors not initialized # ⇒ 2 > exit ~ ruby -W0 /…/bin/pry > $-W # ⇒ 0 >
`$-a` ∈ [true, false]	read-only Denotes whether the auto-split mode was enabled with `-a` command line argument. `-a` switch makes sense when used together with either `-p` or `-n` args. In auto-split mode, Ruby executes `$F = $_.split` at the beginning of each loop. ruby ~ cat > test-a-switch.rb 〈〈EOF # heredoc> # encoding: utf-8 # heredoc> puts "LINE=[#{\$_.strip}]" # heredoc> puts "\$F=#{\$F}" # heredoc> EOF ~ ruby -a -n test-a-switch.rb test-a-switch.rb # LINE=[# encoding: utf-8] # $F=["#", "encoding:", "utf-8"] # LINE=[puts "LINE=#{$_.strip}"] # $F=["puts", "\"LINE=\#{$_.strip},"] # LINE=[puts "$F=#{$F}"] # $F=["puts", "$F=\#{$F}\""] ~ ruby -n test-a-switch.rb test-a-switch.rb # LINE=# encoding: utf-8 # $F= # LINE=puts "LINE=#{$_.strip}" # $F= # LINE=puts "$F=#{$F}" # $F=
`$-d` ∈ [true, false]	read-only Denotes whether the debug mode was enabled with `-d` switch. ruby ~ cat > test-d-switch.rb 〈〈EOF # heredoc> puts "DEBUG MODE: #{\$-d}" # heredoc> EOF ~ ruby -d test-d-switch.rb # Exception `LoadError' at /…/lib/ruby/site_ruby/2.0.0/rubygems.rb:1264 - cannot load such file -- rubygems/defaults/operating_system # Exception `LoadError' at /…/lib/ruby/site_ruby/2.0.0/rubygems.rb:1273 - cannot load such file -- rubygems/defaults/ruby # DEBUG MODE: true
`$-i` ∈ [true, false]	read-only Value of the `-i` command line argument, if given. Defaults to `nil`. When provided, this argument enables inplace-edit mode; the parameter specifies an extension of backup file to be created. ruby ~ cat > test-i-switch.rb << EOF \$_.upcase! puts "i-switch: #{\$-i}" EOF ~ ruby -p -i.bak test-i-switch.rb test-i-switch.rb ~ cat test-i-switch.rb # i-switch: .bak # $_.UPCASE! # i-switch: .bak # PUTS "I-SWITCH: #{$-I}"
`$-l` ∈ [true, false]	read-only Denotes whether the automatic line-ending processing mode was enabled with `-l` switch. Automatic line-endings sets `$\` to the value of `$/`, and (when used with either `-p` or `-n` args) chops every line read using `chop!`. ruby # Could not invent a meaningful example :-(
`$-p` ∈ [true, false]	read-only Denotes whether the “gets loop around” mode was enabled with `-p` switch. `-p` switch acts mostly like `-n` sibling with one exception: it prints the value of variable `$_` at the each end of the loop. For some unknown reason there is no internal global to get aknowledged whether the `-n` command line switch was given. In case it were, Ruby is to assume the following loop around your script, which provides an iteration over filename arguments somewhat like `sed -n` and `awk` do. ruby while gets … end `An example of usage follows:` ruby ~ echo "foo bar baz" \| ruby -p -e '$_.tr! "o-z", "O-Z"' # ⇒ fOO baR baZ
`$-v` `$-w` ∈ [true, false]	read-only Denotes whether the verbose mode was enabled with either `-v` or `-w` switch. ruby ~ cat > test-v-switch.rb 〈〈EOF # heredoc> puts "VERBOSE MODE: #{\$-v}" # heredoc> EOF ~ ruby -v test-v-switch.rb # ruby 2.0.0dev (2012-12-01 trunk 38126) [x86_64-linux] # VERBOSE MODE: true ~
`$.` Fixnum === $.	read-only Number of the last line read from the current input file `ARGF`. ARGF is a stream designed to use in scripts that process files given as command-line arguments or passed in via `STDIN`. ruby ARGV.replace ["file1"] # file1 ≡ 'a\nb\nc\nd' ARGF.readlines # Returns the contents of file1 as an Array $. # ⇒ 4
`$0…$9` String === $0 unless $0.nil? String === $1 unless $1.nil? String === $2 unless $2.nil? String === $3 unless $3.nil? String === $4 unless $4.nil? String === $5 unless $5.nil? String === $6 unless $6.nil? String === $7 unless $7.nil? String === $8 unless $8.nil? String === $9 unless $9.nil?	read-only The `N-th` capture of the previous successful pattern match. Defaults to `nil` if the match failed or if `N` is greater than an amount of captured groups. ruby > "foo bar baz".match(/(foo) (bar)/) # ⇒ > $1 # ⇒ "foo" > $2 # ⇒ "bar" > $3 # ⇒ nil
`$<` ARGF === $<	read-only Read‐only alias for ARGF. ruby > $<.class # ⇒ ARGF.class < Object
`$=` ∈ [true, false]	obsolete ruby > $= # (pry):23: warning: variable $= is no longer effective # ⇒ false
`$>` IO === $>	read-write Standard output stream. ruby > $> = File.new('/tmp/foo', 'w') # ⇒ # -rw-r--r-- 1 am users 0 Feb 27 12:41 /tmp/foo > puts "bar baz" # ⇒ nil > exit ~ cat /tmp/foo # bar baz
`$?` Process::Status === $? unless $?.nil?	read-only Exit status of the last terminated process within current context. ruby > `ls FooBarBaz` # ls: невозможно получить доступ к FooBarBaz: Нет такого файла или каталога # ⇒ "" > $? # ⇒
`$@` Array === $@ unless $@.nil?	read-only thread-local Shorthand to `$!.backtrace` Locals to the `rescue` clause. ruby > 0 / 0 rescue $@ # ⇒ [ # [ 0] "(pry):7:in `/'", # [ 1] "(pry):7:in `__pry__'", # … # [23] "/…/bin/ruby_noexec_wrapper:14:in ` '" # ]
`$\` String === $\ unless $\.nil?	read-write Appended to `Kernel.print` output. Defaults to `nil`, or to `$/` if the `-l` switch was given. ruby > $\='%' # ⇒ "%" > print 'foo', 'bar', 'baz' # ⇒ %foobarbaz%=> nil
`$_` String === $_ unless $_.nil?	read-only thread-local Last `String` read from `IO` by one of `Kernel.gets`, `Kernel.readline` or siblings. Widely used with `-p` and `-n` switches. ruby > gets foo # ⇒ "foo\n" > $_ # ⇒ "foo\n"
`$` </strong></code> <span class="code">String === $ `unless $` .nil?</span> </td> <td> <p><span class="label label-important">read-only</span> <span class="label label-info">thread-local</span> <strong>The rest of the string <em>before</em> the matched substring in the previous successful pattern match.</strong><br> Locals to the pattern match scope.</p> > "foo bar baz".match /bar\|baz/ # ⇒ <MatchData "bar"> > $` # ⇒ "foo " > "foo bar baz".gsub /foo\|bar\|baz/, 'ggg' # ⇒ "ggg ggg ggg" > $` # ⇒ "foo bar " > "foo bar baz".match /foobarbaz/ # ⇒ nil > $` # ⇒ nil </td> </tr> <tr> <td class="tooltipable"> <a id="tilde"></a> <code class="btn btn-large disabled"><strong>$ ~~</strong></code> <span class="code">MatchData === $~~ unless $ .nil?</span> </td> <td> <p><span class="label label-important">read-only</span> <span class="label label-info">thread-local</span> <strong>The <code>MatchData</code> from the previous successful pattern match.</strong><br></p> ~~`> "abc12def34ghijklmno567pqrs".gsub (/\d+/) { \|m\| p $~ } # ⇒ <MatchData "12"> # ⇒ <MatchData "34"> # ⇒ <MatchData "567">`~~ </td> </tr> </tbody> </table> </div> Credits to Jim Neath and runpaint , some examples came from these posts. ← Ruby Blocks: Do-end vs. Braces Ruby Shorthand to Yield Within Blocks → Uses Now CV Projects © 2026 Aleksei Matiushkin · Keyboard shortcuts `g` `h` Go home `g` `b` Go to the blog `g` `p` Go to projects `g` `m` Go to the maze `j` / `k` Move through the current list `n` / `p` Next / previous post or project `/` Focus search `t` Cycle theme `?` Toggle this dialog