# RUBY(1) - man - phpMan

[RUBY(1)](https://www.chedong.com/phpMan.php/man/RUBY/1/markdown)                Ruby Programmer's Reference Guide               [RUBY(1)](https://www.chedong.com/phpMan.php/man/RUBY/1/markdown)

## 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 (like 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 ugli‐
     ness, 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.  Consequently, 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 collected 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 integers are seen as objects.

### Class, inheritance, and methods
             Being an object-oriented language, Ruby naturally has basic features like classes, in‐
             heritance, and methods.

### Singleton methods
             Ruby has the ability to define methods for certain objects.  For example, you can de‐
             fine 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 confu‐
             sion.  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 dif‐
             ferent natural languages and encoded in many different character encodings, without de‐
             pendence on Unicode.

### Bignums
             With built-in bignums, you can for example calculate [factorial(400)](https://www.chedong.com/phpMan.php/man/factorial/400/markdown).

### 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
             In addition to the “builtin libraries” and “standard libraries” that are bundled with
             Ruby, a vast amount of third-party libraries (“gems”) are available via the package
             management system called ‘RubyGems’, namely the [gem(1)](https://www.chedong.com/phpMan.php/man/gem/1/markdown) command.  Visit RubyGems.org
             (**<https://rubygems.org/>**) to find the gems you need, and explore GitHub
             (**<https://github.com/>**) to see how they are being developed and used.

## OPTIONS
     The Ruby interpreter accepts the following command-line options (switches).  They are quite
     similar to those of [perl(1)](https://www.chedong.com/phpMan.php/man/perl/1/markdown).

     **--copyright**    Prints the copyright notice, and quits immediately without running any script.

     **--version**      Prints the version of the Ruby interpreter, and quits immediately without run‐
                    ning any script.

### -0
                    ber. 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
### -X

### -E
     **--encoding** _external_[:_internal_]
                    Specifies the default value(s) for external encodings and internal encoding.
                    Values should be separated with colon (:).

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

     **--external-encoding**=_encoding_
     **--internal-encoding**=_encoding_
                    Specify the default external or internal character encoding

### -F

### -I
                    added to the load-path variable ($:).

### -K
                    (__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
                    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 $*

                    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 and such).  A better construct than $* would be ${1+"$@"}, but it does
                    not work if the script is being interpreted by [csh(1)](https://www.chedong.com/phpMan.php/man/csh/1/markdown).

### -T

### -U
                    UTF-8.

### -W
                    sage 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.  **-W**2
                                  is same as **-w**

### -a -n -p
                    cutes
                          $F = $_.split
                    at beginning of each loop.

### -c
                    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
                    the arguments for a script file name.

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

### -i
                    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
                    means to firstly set $\ to the value of $/, and secondly chops every line read
                    using chomp!.

### -n
                    erate over file name arguments somewhat like **sed** **-n** or **awk**.

                          while gets
                            ...
                          end

### -p
                    end of the loop.  For example:

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

### -r -n
                    **-p**.

### -s
                    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

### -v
                    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
                    the $VERBOSE variable to true.

### -x
                    discarded until the first line that starts with “#!” and contains the string,
                    “ruby”.  Any meaningful switches on that line will be applied.  The end of the
                    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 mes‐
                    sages during compilation.  Only specify this switch you are going to debug the
                    Ruby interpreter.

     **--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 latest 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 considers the variable.

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

     **--dump**=_target_  Dump some information.

                    Prints the specified target.  _target_ can be one of;

                          **version** version description same as **--version**

                          **usage**   brief usage message same as **-h**

                          **help**    Show long help message same as **--help**

                          **syntax**  check of syntax same as **-c** **--yydebug**

                          **yydebug** compiler debug mode, same as **--yydebug**

                                  Only specify this switch if you are going to debug the Ruby inter‐
                                  preter.

                          **parsetree**

                          **parsetree**___**with**___**comment** AST nodes tree

                                  Only specify this switch if you are going to debug the Ruby inter‐
                                  preter.

                          **insns**   disassembled instructions

                                  Only specify this switch if you are going to debug the Ruby inter‐
                                  preter.

     **--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 script arguments
                    (script file or **-e** options) are present, Ruby quits immediately.

## 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.

     And Ruby depends on some RubyGems related environment variables unless RubyGems is disabled.
     See the help of [gem(1)](https://www.chedong.com/phpMan.php/man/gem/1/markdown) as below.

           % gem help

## GC ENVIRONMENT
     The Ruby garbage collector (GC) tracks objects in fixed-sized slots, but each object may have
     auxiliary memory allocations handled by the malloc family of C standard library calls (
     [malloc(3)](https://www.chedong.com/phpMan.php/man/malloc/3/markdown), [calloc(3)](https://www.chedong.com/phpMan.php/man/calloc/3/markdown), and [realloc(3)](https://www.chedong.com/phpMan.php/man/realloc/3/markdown)).  In this documentatation, the "heap" refers to the Ruby
     object heap of fixed-sized slots, while "malloc" refers to auxiliary allocations commonly re‐
     ferred to as the "process heap".  Thus there are at least two possible ways to trigger GC:

           **1**       Reaching the object limit.

           **2**       Reaching the malloc limit.

     In Ruby 2.1, the generational GC was introduced and the limits are divided into young and old
     generations, providing two additional ways to trigger a GC:

           **3**       Reaching the old object limit.

           **4**       Reaching the old malloc limit.

     There are currently 4 possible areas where the GC may be tuned by the following 11 environment
     variables:
     RUBY_GC_HEAP_INIT_SLOTS                Initial allocation slots.  Introduced in Ruby 2.1, de‐
                                            fault: 10000.

     RUBY_GC_HEAP_FREE_SLOTS                Prepare at least this amount of slots after GC.  Allo‐
                                            cate this number slots if there are not enough slots.
                                            Introduced in Ruby 2.1, default: 4096

     RUBY_GC_HEAP_GROWTH_FACTOR             Increase allocation rate of heap slots by this factor.
                                            Introduced in Ruby 2.1, default: 1.8, minimum: 1.0 (no
                                            growth)

     RUBY_GC_HEAP_GROWTH_MAX_SLOTS          Allocation rate is limited to this number of slots, pre‐
                                            venting excessive allocation due to
                                            RUBY_GC_HEAP_GROWTH_FACTOR.  Introduced in Ruby 2.1, de‐
                                            fault: 0 (no limit)

     RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR    Perform a full GC when the number of old objects is more
                                            than R * N, where R is this factor and N is the number
                                            of old objects after the last full GC.  Introduced in
                                            Ruby 2.1.1, default: 2.0

     RUBY_GC_MALLOC_LIMIT                   The initial limit of young generation allocation from
                                            the malloc-family.  GC will start when this limit is
                                            reached.  Default: 16MB

     RUBY_GC_MALLOC_LIMIT_MAX               The maximum limit of young generation allocation from
                                            malloc before GC starts.  Prevents excessive malloc
                                            growth due to RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR.  In‐
                                            troduced in Ruby 2.1, default: 32MB.

     RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR     Increases the limit of young generation malloc calls,
                                            reducing GC frequency but increasing malloc growth until
                                            RUBY_GC_MALLOC_LIMIT_MAX is reached.  Introduced in Ruby
                                            2.1, default: 1.4, minimum: 1.0 (no growth)

     RUBY_GC_OLDMALLOC_LIMIT                The initial limit of old generation allocation from mal‐
                                            loc, a full GC will start when this limit is reached.
                                            Introduced in Ruby 2.1, default: 16MB

     RUBY_GC_OLDMALLOC_LIMIT_MAX            The maximum limit of old generation allocation from mal‐
                                            loc before a full GC starts.  Prevents excessive malloc
                                            growth due to RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR.
                                            Introduced in Ruby 2.1, default: 128MB

     RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR  Increases the limit of old generation malloc allocation,
                                            reducing full GC frequency but increasing malloc growth
                                            until RUBY_GC_OLDMALLOC_LIMIT_MAX is reached.  Intro‐
                                            duced in Ruby 2.1, default: 1.2, minimum: 1.0 (no
                                            growth)

## STACK SIZE ENVIRONMENT
     Stack size environment variables are implementation-dependent and subject to change with dif‐
     ferent versions of Ruby.  The VM stack is used for pure-Ruby code and managed by the virtual
     machine.  Machine stack is used by the operating system and its usage is dependent on C exten‐
     sions as well as C compiler options.  Using lower values for these may allow applications to
     keep more Fibers or Threads running; but increases the chance of SystemStackError exceptions
     and segmentation faults (SIGSEGV).  These environment variables are available since Ruby 2.0.0.
     All values are specified in bytes.

     RUBY_THREAD_VM_STACK_SIZE       VM stack size used at thread creation.  default: 131072 (32-bit
                                     CPU) or 262144 (64-bit)

     RUBY_THREAD_MACHINE_STACK_SIZE  Machine stack size used at thread creation.  default: 524288 or
                                     1048575

     RUBY_FIBER_VM_STACK_SIZE        VM stack size used at fiber creation.  default: 65536 or 131072

     RUBY_FIBER_MACHINE_STACK_SIZE   Machine stack size used at fiber creation.  default: 262144 or
                                     524288

## SEE ALSO
     **<https://www.ruby-lang.org/>**     The official web site.
     **<https://www.ruby-toolbox.com/>**  Comprehensive catalog of Ruby libraries.

## REPORTING BUGS
     ••   Security vulnerabilities should be reported via an email to <_security@ruby-lang.org_>.  Re‐
         ported problems will be published after being fixed.

     ••   Other bugs and feature requests can be reported via the Ruby Issue Tracking System
         (**<https://bugs.ruby-lang.org/>**). Do not report security vulnerabilities via this system be‐
         cause it publishes the vulnerabilities immediately.

## AUTHORS
     Ruby is designed and implemented by Yukihiro Matsumoto <<matz@netlab.jp>>.

     See ⟨**<https://bugs.ruby-lang.org/projects/ruby/wiki/Contributors>**⟩ for contributors to Ruby.

UNIX                            April 14, 2018                            UNIX