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Updated: Wednesday, February 9, 2022

ruby (1)


ruby - oriented scripting language


ruby  [--copyright]  [--version] [-SUacdlnpswvy] [-0[octal]] [-C direc-
tory] [-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]  [--ver-
bose] [--] [program_file] [argument ...]


RUBY(1)                              UNIX                              RUBY(1)

       ruby - Interpreted object-oriented scripting language

       ruby  [--copyright]  [--version] [-SUacdlnpswvy] [-0[octal]] [-C direc-
       tory] [-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]  [--ver-
       bose] [--] [program_file] [argument ...]

       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 ugliness, or you do like the concept of LISP, but
       don't like too many parentheses, Ruby might be your language of choice.

       Ruby's features are as follows:

              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  -  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 refer-
              enced 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 fea-
              tures 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 a `Mix-in'.

              Ruby has iterators for loop abstraction.

              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 languages and encoded in
              many different character encodings, without dependence  on  Uni-

              With  built-in  bignums,  you  can  for example calculate facto-

       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

       Exception handling
              As in Java(tm).

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

       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 manage-
              ment system called `RubyGems', namely the gem(1) 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.

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

              Prints  the copyright notice, and quits immediately without run-
              ning any script.

              Prints the version of the Ruby interpreter,  and  quits  immedi-
              ately without running any script.

              (The  digit  ``zero''.)   Specifies  the  input record separator
              ("$/") as an octal number. If no digit is given, the null  char-
              acter  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 inter-
              nal encoding. Values should be separated with colon (:).

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


              Specify the default external or internal character encoding

       -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  its  name begins with a slash.  This is used to
              emulate #!  on machines that don't support it, in the  following

              #! /usr/ruby/2.6/bin/ruby
              # This line makes the next one a comment in Ruby \
                exec /usr/ruby/2.6/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).

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

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

              Turns on verbose mode at the specified  level  without  printing
              the 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.  -W 2
              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 ``Syn-
              tax OK'' to the standard output.


              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.


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

       -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

       -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"'

       -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/ruby/2.6/bin/ruby -s
              # prints "true" if invoked with `-xyz' switch.
              print "true\n" if $xyz

       -v     Enables verbose mode.  Ruby will print its version at the begin-
              ning  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.

              Tells  Ruby  that  the script is embedded in a message.  Leading
              garbage will be 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.


              DO NOT USE.

              Turns on compiler debug mode.  Ruby will print a bunch of inter-
              nal state messages during compilation.  Only specify this switch
              you are going to debug the Ruby interpreter.


              Disables (or enables) the specified FEATURE.


              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.


              Ignores (or considers)  the  RUBYOPT  environment  variable.  By
              default, Ruby considers the variable.


              Disables (or enables) all features.

              Dump some informations.

              Prints the specified target.  target can be one of;

              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

              compiler debug mode, same as --yydebug

              Only  specify  this  switch  if  you are going to debug the Ruby


              AST nodes tree

              Only specify this switch if you are  going  to  debug  the  Ruby

       insns  disassembled instructions

              Only  specify  this  switch  if  you are going to debug the Ruby

              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.

              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.


              Additional Ruby options.

                RUBYOPT="-w -Ke"

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

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

              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 Ker-

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

              % gem help

       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), calloc(3), and
       realloc(3)) In this documentatation, the  "heap"  refers  to  the  Ruby
       object  heap  of  fixed-sized slots, while "malloc" refers to auxiliary
       allocations commonly referred 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  addi-
              tional 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:

              Initial allocation slots.   Introduced  in  Ruby  2.1,  default:

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

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

              Allocation rate is limited to this number of  slots,  preventing
              excessive  allocation due to RUBY_GC_HEAP_GROWTH_FACTOR.  Intro-
              duced in Ruby 2.1, default: 0 (no limit)

              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

              The initial limit of young generation allocation from  the  mal-
              loc-family.  GC will start when this limit is reached.  Default:

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

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

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

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

              Increases  the limit of old generation malloc allocation, reduc-
              ing  full  GC  frequency  but  increasing  malloc  growth  until
              RUBY_GC_OLDMALLOC_LIMIT_MAX is reached.  Introduced in Ruby 2.1,
              default: 1.2, minimum: 1.0 (no growth)

       Stack size environment variables are implementation-dependent and  sub-
       ject  to  change with different 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.

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

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

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

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

       See attributes(7) for descriptions of the following attributes:

       |Availability   | runtime/ruby-26  |
       |Stability      | Uncommitted      |

              The official web site.

              Comprehensive catalog of Ruby libraries.

       o      Security  vulnerabilities  should be reported via an email to Mt
              security@ruby-lang.org.  Reported  problems  will  be  published
              after being fixed.

       o      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 because it pub-
              lishes the vulnerabilities immediately.

       Ruby is designed  and  implemented  by  Yukihiro  Matsumoto  <matz@net-

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

       The following files specify the installation locations for Ruby:

              Contains the Rubygems repository. Configure the  GEM_HOME  envi-
              ronment  variable  to point to /usr/ruby/2.6/lib/ruby/gems/2.6.0
              as the installation of Rubygems repository.

              Per user location for gems, when installing with the gem install
              option  --user-install  (gem install --user-install ... ).  This
              path is automatically added to GEM_PATH.

              Per user location for gem executables.

              Contains  the  Ruby  executable  as well as other  utility  pro-
              grams,  and  Rubygems  programs.  These programs are linked from
              /usr/bin.  For example: /usr/ruby/2.6/bin/ruby  is  linked  from
              /usr/bin/ruby26,  and  may  be  linked from /usr/bin/ruby if the
              package mediator "ruby" is version  "2.6"  (see  pkg(1)).   Also
              contains  executables  for  any  installed  gems  that have them
              (i.e.: thin, rails, etc).

       Source code for open source software components in Oracle  Solaris  can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source       was       downloaded       from         http://cache.ruby-

       Further information about this software can be found on the open source
       community website at http://www.ruby-lang.org/.

April 14, 2018                               Ruby Programmer's Reference Guide