RUBY(1) Ruby Programmers Reference Guide 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-ori‐
ented 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
($/) as an octal number. If no digit is given, the null
character is taken as the separator. Other switches may
follow the digits. -00 turns Ruby into paragraph mode.
-0777 makes Ruby read whole file at once as a single
string since there is no legal character with that value.
-C directory Causes Ruby to switch to the directory.
-F pattern Specifies input field separator ($;).
-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 standard output.
-d
--debug Turns on debug mode. $DEBUG will be set to true.
-e command Specifies script from command-line while telling Ruby not
to search the rest of arguments for a script file name.
-h
--help Prints a summary of the options.
-i extension Specifies in-place-edit mode. The extension, if speci‐
fied, is added to old file name to make a backup copy.
For example:
% echo matz > /tmp/junk
% cat /tmp/junk
matz
% ruby -p -i.bak -e '$_.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 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 printing its version.
-w Enables verbose mode without printing version message at
the beginning. It sets the $VERBOSE variable to true.
-x[directory] Tells Ruby that the script is embedded in a message.
Leading garbage will be discarded until the first that
starts with “#!” and contains the string, “ruby”. Any
meaningful switches on that line will applied. The end of
script must be specified with either EOF, ^D (control-D),
^Z (control-Z), or reserved word __END__. If the direc‐
tory name is specified, Ruby will switch to that directory
before executing script.
-y
--yydebug Turns on compiler debug mode. Ruby will print a bunch of
internal state messages during compiling scripts. You
don't have to specify this switch, unless you are going to
debug the Ruby interpreter.
ENVIRONMENT
RUBYLIB A colon-separated list of directories that are added to
Ruby's library load path ($:). 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"
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.
AUTHORS
Ruby is designed and implemented by Yukihiro Matsumoto ⟨matz@netlab.jp⟩.
UNIX December 31, 2002 UNIX
