RUBY(1) 1 (ruby programmer's 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] [--crash-report=template] [--] [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 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. 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, 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
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 languages 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
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) 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).
--copyright Prints the copyright notice, and quits immediately without
running any script.
--version Prints the version of the Ruby interpreter, and quits
immediately without running any script.
-0[octal] (The digit "zero".) Specifies the input record separator
($/) as an octal number. If no digit is given, the null
character is taken as the separator. Other switches may
follow the digits. -00 turns Ruby into paragraph mode.
-0777 makes Ruby read whole file at once as a single
string since there is no legal character with that value.
-C directory
-X directory Causes Ruby to switch to the directory.
-E external[:internal]
--encoding external[:internal]
Specifies the default value(s) for external encodings and
internal encoding. Values should be separated with colon
(:).
You can omit the one for internal encodings, then the
value (Encoding.default_internal) will be nil.
--external-encoding=encoding
--internal-encoding=encoding
Specify the default external or internal character
encoding
-F pattern Specifies input field separator ($;).
-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 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).
-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 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. -W2 is the 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.
--backtrace-limit=num
Limits the maximum length of backtraces to num lines
(default -1, meaning no limit).
-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
chomp!.
-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
-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 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 This option is not guaranteed to be compatible.
Turns on compiler debug mode. Ruby will print a bunch of
internal state messages 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 Print version description (same as
--version).
usage Print a brief usage message (same as -h).
help Show long help message (same as --help).
syntax Check syntax (same as -c --yydebug).
Or one of the following, which are intended for debugging
the interpreter:
yydebug Enable compiler debug mode
(same as --yydebug).
parsetree Print a textual
representation of the Ruby
AST for the program.
parsetree_with_comment Print a textual
representation of the Ruby
AST for the program, but
with each node annoted with
the associated Ruby source
code.
insns Print a list of disassembled
bytecode instructions.
insns_without_opt Print the list of
disassembled bytecode
instructions before various
optimizations have been
applied.
--verbose Enables verbose mode without printing version message at
the beginning. It sets the $VERBOSE variable to true. If
this switch is given, and no script arguments (script file
or -e options) are present, Ruby quits immediately.
--crash-report=template
Sets the template of path name to save crash report. See
RUBY_CRASH_REPORT environment variable for details.
ENVIRONMENT
RUBYLIB A colon-separated list of directories that are added to Ruby's
library load path ($:). 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) 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), 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 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. Applies
to all slot sizes. Introduced in
Ruby 2.1, default: 10000.
RUBY_GC_HEAP_%d_INIT_SLOTS Initial allocation of slots in a
specific heap. The available
heaps can be found in the keys of
`GC.stat_heap`. Introduced in
Ruby 3.3.
RUBY_GC_HEAP_FREE_SLOTS 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
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, preventing
excessive allocation due to
RUBY_GC_HEAP_GROWTH_FACTOR.
Introduced in Ruby 2.1, default: 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.
Introduced 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 malloc,
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 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
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. Introduced 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 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 extensions 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: 524288 (32-bit CPU) or 1048575
(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
CRASH REPORT ENVIRONMENT
RUBY_CRASH_REPORT The template of path name to save crash report.
default: none
Naming crash report files
The template can contain % specifiers which are substituted by the
following values when a crash report file is created:
%% A single % character.
%e Basename of executable.
%E Pathname of executable, with slashes (/) replaced by exclamation
marks (!).
%f Basename of the program name, $0.
%F Pathname of the program name, $0, with slashes (/) replaced by
exclamation marks (!).
%p PID of dumped process.
%t Time of dump, expressed as seconds since the Epoch, 1970-01-01
00:00:00 +0000 (UTC).
%NNN A character code in octal.
A single % at the end of the template is dropped from the core filename,
as is the combination of a % followed by any character other than those
listed above. All other characters in the template become a literal part
of the core filename. The template may include '/' characters, which are
interpreted as delimiters for directory names.
Piping crash reports to a program
If the first character of this file is a pipe symbol (|), then the
remainder of the line is interpreted as the command-line for a program
(or script) that is to be executed.
The pipe template is split on spaces into an argument list before the
template parameters are expanded.
SEE ALSO
https://www.ruby-lang.org/ The official web site.
https://www.ruby-toolbox.com/ Comprehensive catalog of Ruby libraries.
REPORTING BUGS
o Security vulnerabilities should be reported via an email to
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 publishes the
vulnerabilities immediately.
AUTHORS
Ruby is designed and implemented by Yukihiro Matsumoto <matz@netlab.jp>.
See <https://github.com/ruby/ruby/graphs/contributors> for contributors
to Ruby.
UNIX April 14, 2018 UNIX
ruby 3.3.1 - Generated Thu May 9 13:52:45 CDT 2024