1RUBY(1)                Ruby Programmers Reference Guide                RUBY(1)
2

NAME

4     ruby — Interpreted object-oriented scripting language
5

SYNOPSIS

7     ruby [--copyright] [--version] [-SUacdlnpswvy] [-0[octal]] [-C directory]
8          [-E external[:internal]] [-F pattern] [-I directory] [-K c]
9          [-T[level]] [-W[level]] [-e command] [-i[extension]] [-r library]
10          [-x[directory]] [-{enable|disable}-FEATURE] [--dump=target]
11          [--verbose] [--] [program_file] [argument ...]
12

DESCRIPTION

14     Ruby is an interpreted scripting language for quick and easy object-ori‐
15     ented programming.  It has many features to process text files and to do
16     system management tasks (like in Perl).  It is simple, straight-forward,
17     and extensible.
18
19     If you want a language for easy object-oriented programming, or you don't
20     like the Perl ugliness, or you do like the concept of LISP, but don't
21     like too many parentheses, Ruby might be your language of choice.
22

FEATURES

24     Ruby's features are as follows:
25
26     Interpretive
27             Ruby is an interpreted language, so you don't have to recompile
28             programs written in Ruby to execute them.
29
30     Variables have no type (dynamic typing)
31             Variables in Ruby can contain data of any type.  You don't have
32             to worry about variable typing.  Consequently, it has a weaker
33             compile time check.
34
35     No declaration needed
36             You can use variables in your Ruby programs without any declara‐
37             tions.  Variable names denote their scope - global, class,
38             instance, or local.
39
40     Simple syntax
41             Ruby has a simple syntax influenced slightly from Eiffel.
42
43     No user-level memory management
44             Ruby has automatic memory management.  Objects no longer refer‐
45             enced from anywhere are automatically collected by the garbage
46             collector built into the interpreter.
47
48     Everything is an object
49             Ruby is a purely object-oriented language, and was so since its
50             creation.  Even such basic data as integers are seen as objects.
51
52     Class, inheritance, and methods
53             Being an object-oriented language, Ruby naturally has basic fea‐
54             tures like classes, inheritance, and methods.
55
56     Singleton methods
57             Ruby has the ability to define methods for certain objects.  For
58             example, you can define a press-button action for certain widget
59             by defining a singleton method for the button.  Or, you can make
60             up your own prototype based object system using singleton meth‐
61             ods, if you want to.
62
63     Mix-in by modules
64             Ruby intentionally does not have the multiple inheritance as it
65             is a source of confusion.  Instead, Ruby has the ability to share
66             implementations across the inheritance tree.  This is often
67             called a ‘Mix-in’.
68
69     Iterators
70             Ruby has iterators for loop abstraction.
71
72     Closures
73             In Ruby, you can objectify the procedure.
74
75     Text processing and regular expressions
76             Ruby has a bunch of text processing features like in Perl.
77
78     M17N, character set independent
79             Ruby supports multilingualized programming. Easy to process texts
80             written in many different natural languages and encoded in many
81             different character encodings, without dependence on Unicode.
82
83     Bignums
84             With built-in bignums, you can for example calculate facto‐
85             rial(400).
86
87     Reflection and domain specific languages
88             Class is also an instance of the Class class. Definition of
89             classes and methods is an expression just as 1+1 is. So your pro‐
90             grams can even write and modify programs.  Thus you can write
91             your application in your own programming language on top of Ruby.
92
93     Exception handling
94             As in Java(tm).
95
96     Direct access to the OS
97             Ruby can use most UNIX system calls, often used in system pro‐
98             gramming.
99
100     Dynamic loading
101             On most UNIX systems, you can load object files into the Ruby
102             interpreter on-the-fly.
103
104     Rich libraries
105             Libraries called "builtin libraries" and "standard libraries" are
106             bundled with Ruby.  And you can obtain more libraries via the
107             package management system called `RubyGems'.
108
109             Moreover there are thousands of Ruby projects on GitHub
110             <https://github.com/languages/Ruby>.
111

OPTIONS

113     Ruby interpreter accepts following command-line options (switches).  They
114     are quite similar to those of perl(1).
115
116     --copyright    Prints the copyright notice.
117
118     --version      Prints the version of Ruby interpreter.
119
120     -0[octal]      (The digit “zero”.)  Specifies the input record separator
121                    ($/) as an octal number. If no digit is given, the null
122                    character is taken as the separator.  Other switches may
123                    follow the digits.  -00 turns Ruby into paragraph mode.
124                    -0777 makes Ruby read whole file at once as a single
125                    string since there is no legal character with that value.
126
127     -C directory
128     -X directory   Causes Ruby to switch to the directory.
129
130     -E external[:internal]
131     --encoding external[:internal]
132                    Specifies the default value(s) for external encodings and
133                    internal encoding. Values should be separated with colon
134                    (:).
135
136                    You can omit the one for internal encodings, then the
137                    value (Encoding.default_internal) will be nil.
138
139     --external-encoding=encoding
140     --internal-encoding=encoding
141                    Specify the default external or internal character encod‐
142                    ing
143
144     -F pattern     Specifies input field separator ($;).
145
146     -I directory   Used to tell Ruby where to load the library scripts.
147                    Directory path will be added to the load-path variable
148                    ($:).
149
150     -K kcode       Specifies KANJI (Japanese) encoding. The default value for
151                    script encodings (__ENCODING__) and external encodings
152                    (Encoding.default_external) will be the specified one.
153                    kcode can be one of
154
155                          e       EUC-JP
156
157                          s       Windows-31J (CP932)
158
159                          u       UTF-8
160
161                          n       ASCII-8BIT (BINARY)
162
163     -S             Makes Ruby use the PATH environment variable to search for
164                    script, unless its name begins with a slash.  This is used
165                    to emulate #! on machines that don't support it, in the
166                    following manner:
167
168                          #! /usr/local/bin/ruby
169                          # This line makes the next one a comment in Ruby \
170                            exec /usr/local/bin/ruby -S $0 $*
171
172     -T[level=1]    Turns on taint checks at the specified level (default 1).
173
174     -U             Sets the default value for internal encodings
175                    (Encoding.default_internal) to UTF-8.
176
177     -W[level=2]    Turns on verbose mode at the specified level without
178                    printing the version message at the beginning. The level
179                    can be;
180
181                          0       Verbose mode is "silence". It sets the
182                                  $VERBOSE to nil.
183
184                          1       Verbose mode is "medium". It sets the
185                                  $VERBOSE to false.
186
187                          2 (default) Verbose mode is "verbose". It sets the
188                                  $VERBOSE to true.  -W2 is same as -w
189
190     -a             Turns on auto-split mode when used with -n or -p.  In
191                    auto-split mode, Ruby executes
192                          $F = $_.split
193                    at beginning of each loop.
194
195     -c             Causes Ruby to check the syntax of the script and exit
196                    without executing. If there are no syntax errors, Ruby
197                    will print “Syntax OK” to the standard output.
198
199     -d
200     --debug        Turns on debug mode.  $DEBUG will be set to true.
201
202     -e command     Specifies script from command-line while telling Ruby not
203                    to search the rest of the arguments for a script file
204                    name.
205
206     -h
207     --help         Prints a summary of the options.
208
209     -i extension   Specifies in-place-edit mode.  The extension, if speci‐
210                    fied, is added to old file name to make a backup copy.
211                    For example:
212
213                          % echo matz > /tmp/junk
214                          % cat /tmp/junk
215                          matz
216                          % ruby -p -i.bak -e '$_.upcase!' /tmp/junk
217                          % cat /tmp/junk
218                          MATZ
219                          % cat /tmp/junk.bak
220                          matz
221
222     -l             (The lowercase letter “ell”.)  Enables automatic line-end‐
223                    ing processing, which means to firstly set $\ to the value
224                    of $/, and secondly chops every line read using chop!.
225
226     -n             Causes Ruby to assume the following loop around your
227                    script, which makes it iterate over file name arguments
228                    somewhat like sed -n or awk.
229
230                          while gets
231                            ...
232                          end
233
234     -p             Acts mostly same as -n switch, but print the value of
235                    variable $_ at the each end of the loop.  For example:
236
237                          % echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
238                          MATZ
239
240     -r library     Causes Ruby to load the library using require.  It is use‐
241                    ful when using -n or -p.
242
243     -s             Enables some switch parsing for switches after script name
244                    but before any file name arguments (or before a --).  Any
245                    switches found there are removed from ARGV and set the
246                    corresponding variable in the script.  For example:
247
248                          #! /usr/local/bin/ruby -s
249                          # prints "true" if invoked with `-xyz' switch.
250                          print "true\n" if $xyz
251
252                    On some systems $0 does not always contain the full path‐
253                    name, so you need the -S switch to tell Ruby to search for
254                    the script if necessary (to handle embedded spaces and
255                    such).  A better construct than $* would be ${1+"$@"}, but
256                    it does not work if the script is being interpreted by
257                    csh(1).
258
259     -v             Enables verbose mode.  Ruby will print its version at the
260                    beginning and set the variable $VERBOSE to true.  Some
261                    methods print extra messages if this variable is true.  If
262                    this switch is given, and no other switches are present,
263                    Ruby quits after printing its version.
264
265     -w             Enables verbose mode without printing version message at
266                    the beginning.  It sets the $VERBOSE variable to true.
267
268     -x[directory]  Tells Ruby that the script is embedded in a message.
269                    Leading garbage will be discarded until the first line
270                    that starts with “#!” and contains the string, “ruby”.
271                    Any meaningful switches on that line will be applied.  The
272                    end of the script must be specified with either EOF, ^D
273                    (control-D), ^Z (control-Z), or the reserved word __END__.
274                    If the directory name is specified, Ruby will switch to
275                    that directory before executing script.
276
277     -y
278     --yydebug      DO NOT USE.
279
280                    Turns on compiler debug mode.  Ruby will print a bunch of
281                    internal state messages during compilation.  Only specify
282                    this switch you are going to debug the Ruby interpreter.
283
284     --disable-FEATURE
285     --enable-FEATURE
286                    Disables (or enables) the specified FEATURE.
287                    --disable-gems
288                    --enable-gems      Disables (or enables) RubyGems
289                                       libraries.  By default, Ruby will load
290                                       the latest version of each installed
291                                       gem. The Gem constant is true if
292                                       RubyGems is enabled, false if other‐
293                                       wise.
294
295                    --disable-rubyopt
296                    --enable-rubyopt   Ignores (or considers) the RUBYOPT
297                                       environment variable. By default, Ruby
298                                       considers the variable.
299
300                    --disable-all
301                    --enable-all       Disables (or enables) all features.
302
303     --dump=target  DO NOT USE.
304
305                    Prints the specified target.  target can be one of;
306
307                          insns   disassembled instructions
308
309                    Only specify this switch if you are going to debug the
310                    Ruby interpreter.
311
312     --verbose      Enables verbose mode without printing version message at
313                    the beginning.  It sets the $VERBOSE variable to true.  If
314                    this switch is given, and no other switches are present,
315                    Ruby quits after printing its version.
316

ENVIRONMENT

318     RUBYLIB         A colon-separated list of directories that are added to
319                     Ruby's library load path ($:). Directories from this
320                     environment variable are searched before the standard
321                     load path is searched.
322
323                     e.g.:
324                           RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"
325
326     RUBYOPT         Additional Ruby options.
327
328                     e.g.
329                           RUBYOPT="-w -Ke"
330
331                     Note that RUBYOPT can contain only -d, -E, -I, -K, -r,
332                     -T, -U, -v, -w, -W, --debug, --disable-FEATURE and
333                     --enable-FEATURE.
334
335     RUBYPATH        A colon-separated list of directories that Ruby searches
336                     for Ruby programs when the -S flag is specified.  This
337                     variable precedes the PATH environment variable.
338
339     RUBYSHELL       The path to the system shell command.  This environment
340                     variable is enabled for only mswin32, mingw32, and OS/2
341                     platforms.  If this variable is not defined, Ruby refers
342                     to COMSPEC.
343
344     PATH            Ruby refers to the PATH environment variable on calling
345                     Kernel#system.
346
347     RUBYLIB_PREFIX  This variable is obsolete.
348
349     And Ruby depends on some RubyGems related environment variables unless
350     RubyGems is disabled.  See the help of gem(1) as bellow.
351
352           % gem help
353

SEE ALSO

355     http://www.ruby-lang.org      The official web site.
356     http://www.rubyforge.org      hosting many open source ruby projects.
357     http://raa.ruby-lang.org      Ruby Application Archive.
358

REPORTING BUGS

360     Security vulnerabilities should be reported via an email to
361     ⟨security@ruby-lang.org⟩.  Reported problems will be published after
362     they've been fixed.
363
364     And you can report other bugs and feature requests via the Ruby Issue
365     Tracking System (http://bugs.ruby-lang.org).  Do not report security vul‐
366     nerabilities via the system because it publishes the vulnerabilities
367     immediately.
368

AUTHORS

370     Ruby is designed and implemented by Yukihiro Matsumoto <matz@netlab.jp>.
371
372     See <http://bugs.ruby-lang.org/wiki/ruby/Contributors> for contributors
373     to Ruby.
374
375UNIX                           November 7, 2012                           UNIX
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