RUBY(1) UNIX RUBY(1)NAMEruby - Interpreted object-oriented scripting language
SYNOPSISruby [--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]] [-Bro enable|disable Brc-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 (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 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 Uni‐
code.
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
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 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 in Rubyforge (
"http://www.rubyforge.org") and RAA ( "http://raa.ruby-
lang.org").
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
("$/") as an octal number. If no digit is given, the null char‐
acter is taken as the separator. Other switches may follow the
digits. -00 turns Ruby into paragraph mode. -0777 makes Ruby
read whole file at once as a single string since there is no
legal character with that value.
-C directory
-X directory
Causes Ruby to switch to the directory.
-E external[]:internal
--encoding external[]:internal
Specifies the default value(s) for external encodings and inter‐
nal encoding. Values should be separated with colon (:).
You can omit the one for internal encodings, then the value
("Encoding.default_internal") will be nil.
-F pattern
Specifies input field separator ("$;").
-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 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 $*
-T[level=1]
Turns on taint checks at the specified level (default 1).
-U Sets the default value for internal encodings ("Encod‐
ing.default_internal") to UTF-8.
-W[level=2]
Turns on verbose mode at the specified level, without printing
version message at the beginning. The level can be;
0 Verbose mode is "silence". It sets the "$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 = $_.split
at beginning of each loop.
-c Causes Ruby to check the syntax of the script and exit without
executing. If there are no syntax errors, Ruby will print ``Syn‐
tax OK'' to the standard output.
-d
--debug
Turns on debug mode. "$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
"$/", and secondly chops every line read using chop!.
-n Causes Ruby to assume the following loop around your script,
which makes it iterate over file name arguments somewhat like
sed -n or awk.
while gets
...
end
-p Acts mostly same as -n switch, but print the value of variable
"$_" 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 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
On some systems "$0" does not always contain the full pathname,
so you need the -S switch to tell Ruby to search for the script
if necessary. To handle embedded spaces or such. A better con‐
struct than "$*" 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 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.
-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 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 inter‐
nal state messages during compiling scripts. You don't have to
specify this switch, unless 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
DO NOT USE.
Prints the specified target. target can be one of;
insns disassembled instructions
You don't have to specify this switch, unless 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 pre‐
cedes 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 Ker‐
nel#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.
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.
· You can report other bugs and feature requests via the Ruby
Issue Tracking System (http://redmine.ruby-lang.org). Do not
report security vulnerabilities via the system because it pub‐
lishes the vulnerabilities immediately.
AUTHORS
Ruby is designed and implemented by Yukihiro Matsumoto <matz@net‐
lab.jp>.
See <http://redmine.ruby-lang.org/wiki/ruby/Contributors> for contribu‐
tors to Ruby.
October 25, 2008 Ruby Programmers Reference Guide RUBY(1)
