NAME¶
ruby —
Interpreted object-oriented
scripting language
SYNOPSIS¶
ruby |
[--copyright]
[--version]
[-SUacdlnpswvy]
[-0[octal]]
[-C
directory]
[-E
external[:internal]]
[-F
pattern]
[-I
directory]
[-K c]
[-T[level]]
[-W[level]]
[-e
command]
[-i[extension]]
[-r
library]
[-x[directory]]
[-{enable|disable}-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
declarations. 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
referenced 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
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 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
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 Unicode.
- Bignums
- With built-in bignums, you can for example calculate
factorial(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 programming.
- 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 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
-
- -X
directory
- Causes Ruby to switch to the directory.
- -E
external[:internal]
-
- --encoding
external[:internal]
- Specifies the default value(s) for external encodings and
internal 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
(
Encoding.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. -W2 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
“Syntax OK” to the standard output.
- -d
-
- --debug
- Turns on debug mode.
$DEBUG
will be
set to true.
- -e
command
- Specifies script from command-line while telling Ruby not
to search the rest of the arguments for a script file name.
- -h
-
- --help
- Prints a summary of the options.
- -i
extension
- Specifies in-place-edit mode. The extension, if specified,
is added to old file name to make a backup copy. For example:
% echo matz > /tmp/junk
% cat /tmp/junk
matz
% ruby -p -i.bak -e '$_.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.
- -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
- 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 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 internal 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 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.
And Ruby depends on some RubyGems related environment variables unless RubyGems
is disabled. See the help of
gem(1) as bellow.
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.
And 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 publishes the
vulnerabilities immediately.
AUTHORS¶
Ruby is designed and implemented by
Yukihiro Matsumoto
⟨matz@netlab.jp⟩.
See <
http://redmine.ruby-lang.org/wiki/ruby/Contributors> for
contributors to Ruby.