RUBY(1) Ruby Programmers Reference Manual RUBY(1)
NAME
ruby - Interpreted object-oriented scripting language
SYNOPSIS
ruby [ --version ] [ -c ] [ -w ] [ -d ] [ -l ]
[ -p ] [ -n ] [ -a ] [ -s ] [ -0[octal] ]
[ -Kc ] [ -ecommand ] [ -Fpattern ]
[ -i[extension] ] [ -Idir ] [ -rlibrary ]
[ -S ] [ -v ] [ -x[directory] ] [ -Cdirectory ]
[ -y] [ -- ] [ programfile ] [ argument ] ...
PREFACE
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.
DESCRIPTION
Ruby's features are as follows:
o Interpretive
Ruby is an interpreted language, so you don't have
to recompile programs written in Ruby to execute
them.
o 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.
o No declaration needed
You can use variables in your Ruby programs without
any declarations. Variable names denote their
scope, local, global, instance, etc.
o Simple syntax
Ruby has a simple syntax influenced slightly from
Eiffel.
o 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.
o 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.
o Class, inheritance, methods
Of course, as an object-oriented language, Ruby has
such basic features like classes, inheritance, and
methods.
o 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.
o 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'.
o Iterators
Ruby has iterators for loop abstraction.
o Closures
In Ruby, you can objectify the procedure.
o Text processing and regular expression
Ruby has a bunch of text processing features like
in Perl.
o Bignums
With built-in bignums, you can for example calcu-
late factorial(400).
o Exception handling
As in Java(tm).
o Direct access to the OS
Ruby can use most UNIX system calls, often used in
system programming.
o Dynamic loading
On most UNIX systems, you can load object files
into the Ruby interpreter on-the-fly.
COMMAND LINE OPTIONS
Ruby interpreter accepts following command-line options
(switches). They are quite similar to those of Perl.
-0[octal]
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 para-
graph mode. - 0777 makes Ruby read whole file at
once as a single string since there is no legal
character with that value.
-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.
--copyright
prints the copyright notice.
-d --debug
turns on debug mode. $DEBUG will set true.
-e command
specifies script from command-line while telling
Ruby to not search argv for script filenames.
-F pattern
specifies input field separator ($;).
-h --help
prints a summary of the options.
-i extension
specifies in-place-edit mode. The extension, if
specified, is added to old filename to make a
backup copy. example:
% echo matz > /tmp/junk
% cat /tmp/junk
matz
% ruby -p -i.bak -e '$_.upcase!' /tmp/junk
% cat /tmp/junk
MATZ
% cat /tmp/junk.bak
matz
-I directory
used to tell Ruby where to load the library
scripts. Directory path will be added to the load-
path variable ($:').
-Kkcode
specifies KANJI (Japanese) encoding.
-l 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 filename
arguments somewhat like sed -n or awk.
while gets
...
end
-p acts mostly same as -n switch, but print the value
of variable $_ at the each end of the loop. exam-
ple:
% echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
MATZ
-r library
causes Ruby to load the library using require. It
is useful with switches -n or -p.
-s enables some switch parsing for switches after
script name but before any filename arguments (or
before a --). Any switches found there are removed
from ARGV and set the corresponding variable in the
script. example:
#! /usr/local/bin/ruby -s
# prints "true" if invoked with `-xyz' switch.
print "true\n" if $xyz
-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 $*
On some systems $0 does not always contain the full
pathname, so you need -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.
-v --verbose
enables verbose mode. Ruby will print its version
at the beginning, and set the variable `$VERBOSE'
to true. Some methods print extra messages if this
variable is true. If this switch is given, and no
other switches are present, Ruby quits after print-
ing its version.
-T[level]
turns on taint checks at the specified level
(default 1).
--version
prints the version of Ruby interpreter.
-w enables verbose mode without printing version mes-
sage at the beginning. It set the `$VERBOSE' vari-
able 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.
-C directory
causes Ruby to switch to the directory.
-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.
AUTHOR
Ruby is designed and implemented by Yukihiro Matsumoto
<matz@netlab.jp>.
2001-12-25 ruby 1.6 RUBY(1)