ruby



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


NAME

     ruby - Interpreted object-oriented scripting language


SYNOPSIS

     ruby [--copyright] [--version] [-Sacdlnpswvy] [-0[octal]] [-C directory]
          [-F pattern] [-I directory] [-K c] [-T[level]] [-e command]
          [-i[extension]] [-r library] [-x[directory]] [--] [program_file]
          [argument ...]


DESCRIPTION

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

     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 much parentheses, Ruby may be the language of your 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.  Consequently, it has a weaker
             compile time check.

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

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

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

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

     Class, inheritance, and methods
             Of course, as an object-oriented language, Ruby has such basic
             features like classes, inheritance, and methods.

     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 meth-
             ods, 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 ‘Mix-in’.

     Iterators
             Ruby has iterators for loop abstraction.

     Closures
             In Ruby, you can objectify the procedure.

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

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

     Exception handling
             As in Java(tm).

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

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


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   Causes Ruby to switch to the directory.

     -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.

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

     -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 arguments for a script file name.

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

     -i extension   Specifies in-place-edit mode.  The extension, if speci-
                    fied, 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-end-
                    ing 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 use-
                    ful 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 path-
                    name, so you need the -S switch to tell Ruby to search for
                    the script if necessary.  To handle embedded spaces or
                    such.  A better construct than $* would be ${1+"$@"}, but
                    it does not work if the script is being interpreted by
                    csh(1).

     -v
     --verbose      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 reserved word __END__.  If the direc-
                    tory name is specified, Ruby will switch to that directory
                    before executing script.

     -y
     --yydebug      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 interpreter.


ENVIRONMENT

     RUBYLIB         A colon-separated list of directories that are appended
                     to Ruby’s library load path ($:).

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

     RUBYOPT         Additional Ruby options.

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

     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.


AUTHORS

     Ruby is designed and implemented by Yukihiro Matsumoto 〈matz@netlab.jp〉.

UNIX                           December 31, 2002                          UNIX

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