RUBY(1) UNIX RUBY(1)
NAME
ruby - Interpreted object-oriented scripting language
SYNOPSIS
ruby [--copyright] [--version] [-Sacdlnpswvy] [-0[octal]] [-C direc‐
tory] [-F pattern] [-I directory] [-K c] [-T[level]] [-e command]
[-i[extension]] [-r library] [-x[directory]] [--] [program_file] [argu‐
ment ...]
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 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 declara‐
tions. 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 refer‐
enced 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-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 ‘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 calculate facto‐
rial(400).
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.
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
("$/") as an octal number. If no digit is given, the null char‐
acter is taken as the separator. Other switches may follow the
digits. -00 turns Ruby into paragraph mode. -0777 makes Ruby
read whole file at once as a single string since there is no
legal character with that value.
-C directory
Causes Ruby to switch to the directory.
-F pattern
Specifies input field separator ("$;").
-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 = $_.split
at beginning of each loop.
-c Causes Ruby to check the syntax of the script and exit without
executing. If there are no syntax errors, Ruby will print ‘‘Syn‐
tax OK’’ to the standard output.
-d
--debug
Turns on debug mode. "$DEBUG" will be set to true.
-e command
Specifies script from command-line while telling Ruby not to
search the rest of 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
--verbose
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 reserved word __END__. If the directory name is speci‐
fied, Ruby will switch to that directory before executing
script.
-y
--yydebug
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.
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 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.
AUTHORS
Ruby is designed and implemented by Yukihiro Matsumoto .
December 31, 2002 Ruby Programmers Reference Guide RUBY(1)