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RUBY(1)                Ruby Programmers Reference Guide                RUBY(1)

NAME
     ruby - Interpreted object-oriented scripting language

SYNOPSIS
     ruby [--copyright] [--version] [-SUacdlnpswvy] [-0[octal]] [-C directory] [-E external[:internal]] [-F pattern]
          [-I directory] [-K c] [-T[level]] [-W[level]] [-e command] [-i[extension]] [-r library] [-x[directory]]
          [-{enable|disable}-FEATURE] [--dump=target] [--verbose] [--] [program_file] [argument ...]

DESCRIPTION
     Ruby is an interpreted scripting language for quick and easy object-oriented programming.  It has many features
     to process text files and to do system management tasks (as in Perl).  It is simple, straight-forward, and exten-
     sible.

     If you want a language for easy object-oriented programming, or you don't like the Perl ugliness, or you do like
     the concept of LISP, but don't like too many parentheses, Ruby might be your language of choice.

FEATURES
     Ruby's features are as follows:

     Interpretive
             Ruby is an interpreted language, so you don't have to recompile programs written in Ruby to execute them.

     Variables have no type (dynamic typing)
             Variables in Ruby can contain data of any type.  You don't have to worry about variable typing.  Conse-
             quently, it has a weaker compile time check.

     No declaration needed
             You can use variables in your Ruby programs without any declarations.  Variable names denote their scope
             - global, class, instance, or local.

     Simple syntax
             Ruby has a simple syntax influenced slightly from Eiffel.

     No user-level memory management
             Ruby has automatic memory management.  Objects no longer referenced from anywhere are automatically col-
             lected by the garbage collector built into the interpreter.

     Everything is an object
             Ruby is a purely object-oriented language, and was so since its creation.  Even such basic data as inte-
             gers are seen as objects.

     Class, inheritance, and methods
             Being an object-oriented language, Ruby naturally has basic features like classes, inheritance, and meth-
             ods.

     Singleton methods
             Ruby has the ability to define methods for certain objects.  For example, you can define a press-button
             action for certain widget by defining a singleton method for the button.  Or, you can make up your own
             prototype based object system using singleton methods, if you want to.

     Mix-in by modules
             Ruby intentionally does not have the multiple inheritance as it is a source of confusion.  Instead, Ruby
             has the ability to share implementations across the inheritance tree.  This is often called a 'Mix-in'.

     Iterators
             Ruby has iterators for loop abstraction.

     Closures
             In Ruby, you can objectify the procedure.

     Text processing and regular expressions
             Ruby has a bunch of text processing features like in Perl.

     M17N, character set independent
             Ruby supports multilingualized programming. Easy to process texts written in many different natural lan-
             guages and encoded in many different character encodings, without dependence on Unicode.

     Bignums
             With built-in bignums, you can for example calculate factorial(400).

     Reflection and domain specific languages
             Class is also an instance of the Class class. Definition of classes and methods is an expression just as
             1+1 is. So your programs can even write and modify programs.  Thus you can write your application in your
             own programming language on top of Ruby.

     Exception handling
             As in Java(tm).

     Direct access to the OS
             Ruby can use most UNIX system calls, often used in system programming.

     Dynamic loading
             On most UNIX systems, you can load object files into the Ruby interpreter on-the-fly.

     Rich libraries
             Libraries called "builtin libraries" and "standard libraries" are bundled with Ruby.  And you can obtain
             more libraries via the package management system called 'RubyGems'.

             Moreover there are thousands of Ruby projects in Rubyforge (http://www.rubyforge.org) and RAA
             (http://raa.ruby-lang.org).

OPTIONS
     Ruby interpreter accepts following command-line options (switches).  They are quite similar to those of perl(1).

     --copyright    Prints the copyright notice.

     --version      Prints the version of Ruby interpreter.

     -0[octal]      (The digit "zero".)  Specifies the input record separator ($/) as an octal number. If no digit is
                    given, the null character is taken as the separator.  Other switches may follow the digits.  -00
                    turns Ruby into paragraph mode.  -0777 makes Ruby read whole file at once as a single string since
                    there is no legal character with that value.

     -C directory
     -X directory   Causes Ruby to switch to the directory.

     -E external[:internal]
     --encoding external[:internal]
                    Specifies the default value(s) for external encodings and internal encoding. Values should be sep-
                    arated with colon (:).

                    You can omit the one for internal encodings, then the value (Encoding.default_internal) will be
                    nil.

     -F pattern     Specifies input field separator ($;).

     -I directory   Used to tell Ruby where to load the library scripts.  Directory path will be added to the load-
                    path variable ($:).

     -K kcode       Specifies KANJI (Japanese) encoding. The default value for script encodings (__ENCODING__) and
                    external encodings (Encoding.default_external) will be the specified one. kcode can be one of

                          e       EUC-JP

                          s       Windows-31J (CP932)

                          u       UTF-8

                          n       ASCII-8BIT (BINARY)

     -S             Makes Ruby use the PATH environment variable to search for script, unless if its name begins with
                    a slash.  This is used to emulate #! on machines that don't support it, in the following manner:

                          #! /usr/local/bin/ruby
                          # This line makes the next one a comment in Ruby \
                            exec /usr/local/bin/ruby -S $0 $*

     -T[level=1]    Turns on taint checks at the specified level (default 1).

     -U             Sets the default value for internal encodings (Encoding.default_internal) to UTF-8.

     -W[level=2]    Turns on verbose mode at the specified level, without printing version message at the beginning.
                    The level can be;

                          0       Verbose mode is "silence". It sets the $VERBOSE to nil.

                          1       Verbose mode is "medium". It sets the $VERBOSE to false.

                          2 (default) Verbose mode is "verbose". It sets the $VERBOSE to true.  -W2 is same as -w

     -a             Turns on auto-split mode when used with -n or -p.  In auto-split mode, Ruby executes
                          $F = $_.split
                    at beginning of each loop.

     -c             Causes Ruby to check the syntax of the script and exit without executing. If there are no syntax
                    errors, Ruby will print "Syntax OK" to the standard output.

     -d
     --debug        Turns on debug mode.  $DEBUG will be set to true.

     -e command     Specifies script from command-line while telling Ruby not to search the rest of the arguments for
                    a script file name.

     -h
     --help         Prints a summary of the options.

     -i extension   Specifies in-place-edit mode.  The extension, if specified, is added to old file name to make a
                    backup copy.  For example:

                          % echo matz > /tmp/junk
                          % cat /tmp/junk
                          matz
                          % ruby -p -i.bak -e '$_.upcase!' /tmp/junk
                          % cat /tmp/junk
                          MATZ
                          % cat /tmp/junk.bak
                          matz

     -l             (The lowercase letter "ell".)  Enables automatic line-ending processing, which means to firstly
                    set $\ to the value of $/, and secondly chops every line read using chop!.

     -n             Causes Ruby to assume the following loop around your script, which makes it iterate over file name
                    arguments somewhat like sed -n or awk.

                          while gets
                            ...
                          end

     -p             Acts mostly same as -n switch, but print the value of variable $_ at the each end of the loop.
                    For example:

                          % echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
                          MATZ

     -r library     Causes Ruby to load the library using require.  It is useful when using -n or -p.

     -s             Enables some switch parsing for switches after script name but before any file name arguments (or
                    before a --).  Any switches found there are removed from ARGV and set the corresponding variable
                    in the script.  For example:

                          #! /usr/local/bin/ruby -s
                          # prints "true" if invoked with '-xyz' switch.
                          print "true\n" if $xyz

                    On some systems $0 does not always contain the full pathname, so you need the -S switch to tell
                    Ruby to search for the script if necessary.  To handle embedded spaces or such.  A better con-
                    struct than $* would be ${1+"$@"}, but it does not work if the script is being interpreted by
                    csh(1).

     -v             Enables verbose mode.  Ruby will print its version at the beginning, and set the variable $VERBOSE
                    to true.  Some methods print extra messages if this variable is true.  If this switch is given,
                    and no other switches are present, Ruby quits after printing its version.

     -w             Enables verbose mode without printing version message at the beginning.  It sets the $VERBOSE
                    variable to true.

     -x[directory]  Tells Ruby that the script is embedded in a message.  Leading garbage will be discarded until the
                    first that starts with "#!" and contains the string, "ruby".  Any meaningful switches on that line
                    will applied.  The end of script must be specified with either EOF, ^D (control-D), ^Z
                    (control-Z), or the reserved word __END__.  If the directory name is specified, Ruby will switch
                    to that directory before executing script.

     -y
     --yydebug      DO NOT USE.

                    Turns on compiler debug mode.  Ruby will print a bunch of internal state messages during compiling
                    scripts.  You don't have to specify this switch, unless you are going to debug the Ruby inter-
                    preter.

     --disable-FEATURE
     --enable-FEATURE
                    Disables (or enables) the specified FEATURE.
                    --disable-gems
                    --enable-gems      Disables (or enables) RubyGems libraries.  By default, Ruby will load the lat-
                                       est version of each installed gem. The Gem constant is true if RubyGems is
                                       enabled, false if otherwise.

                    --disable-rubyopt
                    --enable-rubyopt   Ignores (or considers) the RUBYOPT environment variable. By default, Ruby con-
                                       siders the variable.

                    --disable-all
                    --enable-all       Disables (or enables) all features.

     --dump=target  DO NOT USE.

                    Prints the specified target.  target can be one of;

                          insns   disassembled instructions

                    You don't have to specify this switch, unless you are going to debug the Ruby interpreter.

     --verbose      Enables verbose mode without printing version message at the beginning.  It sets the $VERBOSE
                    variable to true.  If this switch is given, and no other switches are present, Ruby quits after
                    printing its version.

ENVIRONMENT
     RUBYLIB         A colon-separated list of directories that are added to Ruby's library load path ($:).
                     Directories from this environment variable are searched before the standard load path is
                     searched.

                     e.g.:
                           RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"

     RUBYOPT         Additional Ruby options.

                     e.g.
                           RUBYOPT="-w -Ke"

                     Note that RUBYOPT can contain only -d, -E, -I, -K, -r, -T, -U, -v, -w, -W, --debug,
                     --disable-FEATURE and --enable-FEATURE.

     RUBYPATH        A colon-separated list of directories that Ruby searches for Ruby programs when the -S flag is
                     specified.  This variable precedes the PATH environment variable.

     RUBYSHELL       The path to the system shell command.  This environment variable is enabled for only mswin32,
                     mingw32, and OS/2 platforms.  If this variable is not defined, Ruby refers to COMSPEC.

     PATH            Ruby refers to the PATH environment variable on calling Kernel#system.

     RUBYLIB_PREFIX  This variable is obsolete.

     And Ruby depends on some RubyGems related environment variables unless RubyGems is disabled.  See the help of
     gem(1) as bellow.

           % gem help

SEE ALSO
     http://www.ruby-lang.org      The official web site.
     http://www.rubyforge.org      hosting many open source ruby projects.
     http://raa.ruby-lang.org      Ruby Application Archive.

REPORTING BUGS
     Security vulnerabilities should be reported via an email to <securityATruby-lang.org>.  Reported problems will be
     published after they've been fixed.

     And you can report other bugs and feature requests via the Ruby Issue Tracking System (http://redmine.ruby-
     lang.org).  Do not report security vulnerabilities via the system because it publishes the vulnerabilities imme-
     diately.

AUTHORS
     Ruby is designed and implemented by Yukihiro Matsumoto <matzATnetlab.jp>.

     See <http://redmine.ruby-lang.org/wiki/ruby/Contributors> for contributors to Ruby.

UNIX                           October 25, 2008                           UNIX