[DOC] Globals doc (#8445)
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Burdette Lamar
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doc/globals.rdoc
480
doc/globals.rdoc
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# -*- mode: rdoc; coding: utf-8; fill-column: 74; -*-
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== Pre-Defined Global Variables
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== Pre-defined global variables
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Some of the pre-defined global variables have synonyms
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that are available via module Engish.
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For each of those, the \English synonym is given.
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$!:: The Exception object set by Kernel#raise.
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$@:: The same as <code>$!.backtrace</code>.
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$~:: The information about the last match in the current scope (thread-local and frame-local).
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$&:: The string matched by the last successful match.
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$`:: The string to the left of the last successful match.
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$':: The string to the right of the last successful match.
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$+:: The highest group matched by the last successful match.
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$1:: The Nth group of the last successful match. May be > 1.
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$=:: This variable is no longer effective. Deprecated.
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$/:: The input record separator, newline by default. Aliased to $-0.
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$\:: The output record separator for Kernel#print and IO#write. Default is +nil+.
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$,:: The output field separator for Kernel#print and Array#join. Non-nil $, will be deprecated.
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$;:: The default separator for String#split. Non-nil $; will be deprecated. Aliased to $-F.
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$.:: The current input line number of the last file that was read.
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$<:: The same as ARGF.
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$>:: The default output stream for Kernel#print and Kernel#printf. $stdout by default.
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$_:: The last input line of string by gets or readline.
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$0:: Contains the name of the script being executed. May be assignable.
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$*:: The same as ARGV.
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$$:: The process number of the Ruby running this script. Same as Process.pid.
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$?:: The status of the last executed child process (thread-local).
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$LOAD_PATH:: Load path for searching Ruby scripts and extension libraries used
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by Kernel#load and Kernel#require. Aliased to $: and $-I.
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Has a singleton method <code>$LOAD_PATH.resolve_feature_path(feature)</code>
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that returns [+:rb+ or +:so+, path], which resolves the feature to
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the path the original Kernel#require method would load.
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$LOADED_FEATURES:: The array contains the module names loaded by require.
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Aliased to $".
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$DEBUG:: The debug flag, which is set by the <tt>-d</tt> switch. Enabling debug
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output prints each exception raised to $stderr (but not its
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backtrace). Setting this to a true value enables debug output as
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if <tt>-d</tt> were given on the command line. Setting this to a false
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value disables debug output. Aliased to $-d.
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$FILENAME:: Current input filename from ARGF. Same as ARGF.filename.
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$stderr:: The current standard error output.
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$stdin:: The current standard input.
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$stdout:: The current standard output.
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$VERBOSE:: The verbose flag, which is set by the <tt>-w</tt> or <tt>-v</tt> switch.
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Setting this to a true value enables warnings as if <tt>-w</tt> or <tt>-v</tt> were given
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on the command line. Setting this to +nil+ disables warnings,
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including from Kernel#warn. Aliased to $-v and $-w.
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$-a:: True if option <tt>-a</tt> is set. Read-only variable.
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$-i:: In in-place-edit mode, this variable holds the extension, otherwise +nil+.
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$-l:: True if option <tt>-l</tt> is set. Read-only variable.
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$-p:: True if option <tt>-p</tt> is set. Read-only variable.
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To use the module:
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== Pre-defined global constants
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require 'English'
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STDIN:: The standard input. The default value for $stdin.
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STDOUT:: The standard output. The default value for $stdout.
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STDERR:: The standard error output. The default value for $stderr.
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ENV:: The hash contains current environment variables.
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ARGF:: The virtual concatenation of the files given on command line (or from $stdin if no files were given).
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ARGV:: An Array of command line arguments given for the script.
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DATA:: The file object of the script, pointing just after <code>__END__</code>.
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TOPLEVEL_BINDING:: The Binding of the top level scope.
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RUBY_VERSION:: The Ruby language version.
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RUBY_RELEASE_DATE:: The release date string.
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RUBY_PLATFORM:: The platform identifier.
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RUBY_PATCHLEVEL:: The patchlevel for this Ruby. If this is a development build of Ruby the patchlevel will be -1.
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RUBY_REVISION:: The GIT commit hash for this Ruby.
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RUBY_COPYRIGHT:: The copyright string for Ruby.
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RUBY_ENGINE:: The name of the Ruby implementation.
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RUBY_ENGINE_VERSION:: The version of the Ruby implementation.
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RUBY_DESCRIPTION:: The same as <tt>ruby --version</tt>, a String describing various aspects of the Ruby implementation.
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=== Exceptions
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==== <tt>$!</tt> (\Exception)
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Contains the Exception object set by Kernel#raise:
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begin
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raise RuntimeError.new('Boo!')
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rescue RuntimeError
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p $!
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end
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Output:
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#<RuntimeError: Boo!>
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English - <tt>$ERROR_INFO</tt>
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==== <tt>$@</tt> (Backtrace)
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Same as <tt>$!.backtrace</tt>;
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returns an array of backtrace positions:
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begin
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raise RuntimeError.new('Boo!')
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rescue RuntimeError
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pp $@.take(4)
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end
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Output:
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["(irb):338:in `<top (required)>'",
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"/snap/ruby/317/lib/ruby/3.2.0/irb/workspace.rb:119:in `eval'",
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"/snap/ruby/317/lib/ruby/3.2.0/irb/workspace.rb:119:in `evaluate'",
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"/snap/ruby/317/lib/ruby/3.2.0/irb/context.rb:502:in `evaluate'"]
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English - <tt>$ERROR_POSITION</tt>.
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=== Pattern Matching
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These global variables store information about the most recent
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successful match in the current scope.
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For details and examples,
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see {Regexp Global Variables}[rdoc-ref:Regexp@Global+Variables].
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==== <tt>$~</tt> (\MatchData)
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MatchData object created from the match;
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thread-local and frame-local.
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English - <tt>$LAST_MATCH_INFO</tt>.
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==== <tt>$&</tt> (Matched Substring)
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The matched string.
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English - <tt>$MATCH</tt>.
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==== <tt>$`</tt> (Pre-Match Substring)
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The string to the left of the match.
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English - <tt>$PREMATCH</tt>.
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==== <tt>$'</tt> (Post-Match Substring)
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The string to the right of the match.
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English - <tt>$POSTMATCH</tt>.
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==== <tt>$+</tt> (Last Matched Group)
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The last group matched.
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English - <tt>$LAST_PAREN_MATCH</tt>.
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==== <tt>$1</tt>, <tt>$2</tt>, \Etc. (Matched Group)
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For <tt>$_n_</tt> the _nth_ group of the match.
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No \English.
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=== Separators
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==== <tt>$/</tt> (Input Record Separator)
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An input record separator, initially newline.
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English - <tt>$INPUT_RECORD_SEPARATOR</tt>, <tt>$RS</tt>.
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Aliased as <tt>$-0</tt>.
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==== <tt>$;</tt> (Input Field Separator)
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An input field separator, initially +nil+.
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English - <tt>$FIELD_SEPARATOR</tt>, <tt>$FS</tt>.
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Aliased as <tt>$-F</tt>.
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==== <tt>$\\</tt> (Output Record Separator)
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An output record separator, initially +nil+.
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English - <tt>$OUTPUT_RECORD_SEPARATOR</tt>, <tt>$ORS</tt>.
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=== Streams
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==== <tt>$stdin</tt> (Standard Input)
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The current standard input stream; initially:
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$stdin # => #<IO:<STDIN>>
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==== <tt>$stdout</tt> (Standard Output)
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The current standard output stream; initially:
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$stdout # => #<IO:<STDOUT>>
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==== <tt>$stderr</tt> (Standard Error)
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The current standard error stream; initially:
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$stderr # => #<IO:<STDERR>>
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==== <tt>$<</tt> (\ARGF or $stdin)
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Points to stream ARGF if not empty, else to stream $stdin; read-only.
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English - <tt>$DEFAULT_INPUT</tt>.
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==== <tt>$></tt> (Default Standard Output)
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An output stream, initially <tt>$stdout</tt>.
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English - <tt>$DEFAULT_OUTPUT
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==== <tt>$.</tt> (Input Position)
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The input position (line number) in the most recently read stream.
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English - <tt>$INPUT_LINE_NUMBER</tt>, <tt>$NR</tt>
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==== <tt>$_</tt> (Last Read Line)
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The line (string) from the most recently read stream.
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English - <tt>$LAST_READ_LINE</tt>.
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=== Processes
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==== <tt>$0</tt>
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Initially, contains the name of the script being executed;
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may be reassigned.
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==== <tt>$*</tt> (\ARGV)
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Points to ARGV.
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English - <tt>$ARGV</tt>.
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==== <tt>$$</tt> (Process ID)
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The process ID of the current process. Same as Process.pid.
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English - <tt>$PROCESS_ID</tt>, <tt>$PID</tt>.
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==== <tt>$?</tt> (Child Status)
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Initially +nil+, otherwise the Process::Status object
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created for the most-recently exited child process;
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thread-local.
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English - <tt>$CHILD_STATUS</tt>.
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==== <tt>$LOAD_PATH</tt> (Load Path)
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Contains the array of paths to be searched
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by Kernel#load and Kernel#require.
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Singleton method <tt>$LOAD_PATH.resolve_feature_path(feature)</tt>
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returns:
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- <tt>[:rb, _path_]</tt>, where +path+ is the path to the Ruby file
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to be loaded for the given +feature+.
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- <tt>[:so+ _path_]</tt>, where +path+ is the path to the shared object file
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to be loaded for the given +feature+.
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- +nil+ if there is no such +feature+ and +path+.
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Examples:
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$LOAD_PATH.resolve_feature_path('timeout')
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# => [:rb, "/snap/ruby/317/lib/ruby/3.2.0/timeout.rb"]
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$LOAD_PATH.resolve_feature_path('date_core')
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# => [:so, "/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/date_core.so"]
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$LOAD_PATH.resolve_feature_path('foo')
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# => nil
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Aliased as <tt>$:</tt> and <tt>$-I</tt>.
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==== <tt>$LOADED_FEATURES</tt>
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Contains an array of the paths to the loaded files:
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$LOADED_FEATURES.take(10)
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# =>
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["enumerator.so",
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"thread.rb",
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"fiber.so",
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"rational.so",
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"complex.so",
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"ruby2_keywords.rb",
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"/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/enc/encdb.so",
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"/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/enc/trans/transdb.so",
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"/snap/ruby/317/lib/ruby/3.2.0/x86_64-linux/rbconfig.rb",
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"/snap/ruby/317/lib/ruby/3.2.0/rubygems/compatibility.rb"]
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Aliased as <tt>$"</tt>.
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=== Debugging
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==== <tt>$FILENAME</tt>
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The value returned by method ARGF.filename.
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==== <tt>$DEBUG</tt>
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Initially +true+ if command-line option <tt>-d</tt> or <tt>--debug</tt> is given,
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otherwise initially +false+;
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may be set to either value in the running program.
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When +true+, prints each raised exception to <tt>$stderr</tt>.
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Aliased as <tt>$-d</tt>.
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==== <tt>$VERBOSE</tt>
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Initially +true+ if command-line option <tt>-v</tt> or <tt>-w</tt> is given,
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otherwise initially +false+;
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may be set to either value, or to +nil+, in the running program.
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When +true+, enables Ruby warnings.
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When +nil+, disables warnings, including those from Kernel#warn.
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Aliased as <tt>$-v</tt> and <tt>$-w</tt>.
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=== Other Variables
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==== <tt>$-a</tt>
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Whether command-line option <tt>-a</tt> was given; read-only.
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==== <tt>$-i</tt>
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Contains the extension given with command-line option <tt>-i</tt>,
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or +nil+ if none.
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==== <tt>$-l</tt>
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Whether command-line option <tt>-l</tt> was set; read-only.
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==== <tt>$-p</tt>
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Whether command-line option <tt>-p</tt> was given; read-only.
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=== Deprecated
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==== <tt>$=</tt>
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==== <tt>$,</tt>
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== Pre-Defined Global Constants
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== Streams
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==== <tt>STDIN</tt>
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The standard input stream (the default value for <tt>$stdin</tt>):
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STDIN # => #<IO:<STDIN>>
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==== <tt>STDOUT</tt>
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The standard output stream (the default value for <tt>$stdout</tt>):
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STDOUT # => #<IO:<STDOUT>>
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==== <tt>STDERR</tt>
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The standard error stream (the default value for <tt>$stderr</tt>):
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STDERR # => #<IO:<STDERR>>
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=== Enviroment
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==== <tt>ENV</tt>
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A hash of the contains current environment variables names and values:
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ENV.take(5)
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# =>
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[["COLORTERM", "truecolor"],
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["DBUS_SESSION_BUS_ADDRESS", "unix:path=/run/user/1000/bus"],
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["DESKTOP_SESSION", "ubuntu"],
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["DISPLAY", ":0"],
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["GDMSESSION", "ubuntu"]]
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==== <tt>ARGF</tt>
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The virtual concatenation of the files given on the command line,
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or from <tt>$stdin</tt> if no files were given.
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==== <tt>ARGV</tt>
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An array of the given command-line arguments.
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==== <tt>TOPLEVEL_BINDING</tt>
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The Binding of the top level scope:
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TOPLEVEL_BINDING # => #<Binding:0x00007f58da0da7c0>
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==== <tt>RUBY_VERSION</tt>
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The Ruby version:
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RUBY_VERSION # => "3.2.2"
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==== <tt>RUBY_RELEASE_DATE</tt>
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The release date string:
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RUBY_RELEASE_DATE # => "2023-03-30"
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==== <tt>RUBY_PLATFORM</tt>
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The platform identifier:
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RUBY_PLATFORM # => "x86_64-linux"
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==== <tt>RUBY_PATCHLEVEL</tt>
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The integer patch level for this Ruby:
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RUBY_PATCHLEVEL # => 53
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For a development build the patch level will be -1.
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==== <tt>RUBY_REVISION</tt>
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The git commit hash for this Ruby:
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RUBY_REVISION # => "e51014f9c05aa65cbf203442d37fef7c12390015"
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==== <tt>RUBY_COPYRIGHT</tt>
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The copyright string:
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RUBY_COPYRIGHT
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# => "ruby - Copyright (C) 1993-2023 Yukihiro Matsumoto"
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==== <tt>RUBY_ENGINE</tt>
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The name of the Ruby implementation:
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RUBY_ENGINE # => "ruby"
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==== <tt>RUBY_ENGINE_VERSION</tt>
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The version of the Ruby implementation:
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RUBY_ENGINE_VERSION # => "3.2.2"
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==== <tt>RUBY_DESCRIPTION</tt>
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The description of the Ruby implementation:
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RUBY_DESCRIPTION
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# => "ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]"
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=== Embedded \Data
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==== <tt>DATA</tt>
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Defined if and only if the program has this line:
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__END__
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When defined, <tt>DATA</tt> is a File object
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containing the lines following the <tt>__END__</tt>,
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positioned at the first of those lines:
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p DATA
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DATA.each_line { |line| p line }
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__END__
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Foo
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Bar
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Baz
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Output:
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#<File:t.rb>
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"Foo\n"
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"Bar\n"
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"Baz\n"
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