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RUBY(1) UNIX RUBY(1)
NAME
ruby - Interpreted object-oriented scripting language
SYNOPSIS
ruby [--copyright] [--version] [-Sacdlnpswvy] [-0[octal]]
[-C directory] [-F pattern] [-I directory] [-K c]
[-T[level]] [-e command] [-i[extension]] [-r library]
[-x[directory]] [--] [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 program-
ming, or you don't like the Perl ugliness, or you do like
the concept of LISP, but don't like too much parentheses,
Ruby may be the language of your 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, local, global, instance, etc.
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 the purely object-oriented language, and
was so since its creation. Even such basic data as
integers are seen as objects.
Class, inheritance, and methods
Of course, as an object-oriented language, Ruby has
such 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-but-
ton action for certain widget by defining a single-
ton method for the button. Or, you can make up
your own prototype based object system using sin-
gleton 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 implementa-
tions across the inheritance tree. This is often
called `Mix-in'.
Iterators
Ruby has iterators for loop abstraction.
Closures
In Ruby, you can objectify the procedure.
Text processing and regular expression
Ruby has a bunch of text processing features like
in Perl.
Bignums
With built-in bignums, you can for example calcu-
late factorial(400).
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.
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 ("$/") as an octal number. If no digit is
given, the null character is taken as the separa-
tor. Other switches may follow the digits. -00
turns Ruby into paragraph mode. -0777 makes Ruby
read whole file at once as a single string since
there is no legal character with that value.
-C directory
Causes Ruby to switch to the directory.
-F pattern
Specifies input field separator ("$;").
-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.
-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]
Turns on taint checks at the specified level
(default 1).
-a Turns on auto-split mode when used with -n or -p.
In auto-split mode, Ruby executes
$F = $_.split
at beginning of each loop.
-c Causes Ruby to check the syntax of the script and
exit without executing. If there are no syntax
errors, Ruby will print ``Syntax OK'' to the stan-
dard output.
-d
--debug
Turns on debug mode. "$DEBUG" will be set to true.
-e command
Specifies script from command-line while telling
Ruby not to search the rest of 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 "$0" does not always contain the
full pathname, so you need the -S switch to tell
Ruby to search for the script if necessary. To
handle embedded spaces or such. A better construct
than "$*" would be ${1+"$@"}, but it does not work
if the script is being interpreted by csh(1).
-v
--verbose
Enables verbose mode. Ruby will print its version
at the beginning, and set the variable "$VERBOSE"
to true. Some methods print extra messages if this
variable is true. If this switch is given, and no
other switches are present, Ruby quits after print-
ing its version.
-w Enables verbose mode without printing version mes-
sage at the beginning. It sets the "$VERBOSE"
variable to true.
-x[directory]
Tells Ruby that the script is embedded in a mes-
sage. 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 spec-
ified with either EOF, "^D" ("control-D"), "^Z"
("control-Z"), or reserved word __END__. If the
directory name is specified, Ruby will switch to
that directory before executing script.
-y
--yydebug
Turns on compiler debug mode. Ruby will print a
bunch of internal state messages during compiling
scripts. You don't have to specify this switch,
unless you are going to debug the Ruby interpreter.
ENVIRONMENT
RUBYLIB
A colon-separated list of directories that are
appended to Ruby's library load path ("$:").
e.g.:
RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"
RUBYOPT
Additional Ruby options.
e.g.
RUBYOPT="-w -Ke"
RUBYPATH
A colon-separated list of directories that Ruby
searches for Ruby programs when the -S flag is
specified. This variable precedes the PATH envi-
ronment variable.
RUBYSHELL
The path to the system shell command. This envi-
ronment 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.
AUTHORS
Ruby is designed and implemented by Yukihiro Matsumoto
.
December 31, 2002Ruby Programmers Reference Guide RUBY(1)