RUBY(1) Ruby Programmers Reference Guide RUBY(1)NAMEruby — Interpreted object-oriented scripting language
SYNOPSISruby [--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-ori‐
ented 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 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’.
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 facto‐
rial(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 pro‐
grams 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 pro‐
gramming.
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 on GitHub
<https://github.com/languages/Ruby>.
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
($/) as an octal number. If no digit is given, the null
character is taken as the separator. Other switches may
follow the digits. -00 turns Ruby into paragraph mode.
-0777 makes Ruby read whole file at once as a single
string since there is no legal character with that value.
-C directory
-X directory Causes Ruby to switch to the directory.
-E external[:internal]
--encoding external[:internal]
Specifies the default value(s) for external encodings and
internal encoding. Values should be separated with colon
(:).
You can omit the one for internal encodings, then the
value (Encoding.default_internal) will be nil.
--external-encoding=encoding
--internal-encoding=encoding
Specify the default external or internal character encod‐
ing
-F pattern Specifies input field separator ($;).
-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 $*
-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 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. $DEBUG will be set to true.
-e command Specifies script from command-line while telling Ruby not
to search the rest of the arguments for a script file
name.
-h
--help Prints a summary of the options.
-i extension Specifies in-place-edit mode. The extension, if speci‐
fied, is added to old file name to make a backup copy.
For example:
% echo matz > /tmp/junk
% cat /tmp/junk
matz
% ruby-p -i.bak -e '$_.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 and
such). A better construct 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 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 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 other‐
wise.
--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 DO NOT USE.
Prints the specified target. target can be one of;
insns disassembled instructions
Only specify this switch if 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.
https://github.com/languages/Ruby Ruby projects on Github.
REPORTING BUGS
Security vulnerabilities should be reported via an email to
⟨security@ruby-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://bugs.ruby-lang.org). Do not report security vul‐
nerabilities via the system because it publishes the vulnerabilities
immediately.
AUTHORS
Ruby is designed and implemented by Yukihiro Matsumoto ⟨matz@netlab.jp⟩.
See <http://bugs.ruby-lang.org/wiki/ruby/Contributors> for contributors
to Ruby.
UNIX November 7, 2012 UNIX
