Mixin module providing HTML generation methods.
For example,
cgi.a("http://www.example.com") { "Example" } # => "<A HREF=\"http://www.example.com\">Example</A>"
Modules Html3, Html4, etc., contain more basic HTML-generation methods (#title, #h1, etc.).
See class CGI for a detailed example.
Net::HTTP exception class. You cannot use Net::HTTPExceptions directly; instead, you must use its subclasses.
Keyword completion module. This allows partial arguments to be specified and resolved against a list of acceptable values.
If you add a method, keep in mind two things: (1) the first argument will always be a list of nodes from which to filter. In the case of context methods (such as position), the function should return an array with a value for each child in the array. (2) all method calls from XML will have “-” replaced with “_”. Therefore, in XML, “local-name()” is identical (and actually becomes) “local_name()”
A complex number can be represented as a paired real number with imaginary unit; a+bi. Where a is real part, b is imaginary part and i is imaginary unit. Real a equals complex a+0i mathematically.
Complex object can be created as literal, and also by using Kernel#Complex, Complex::rect, Complex::polar or to_c method.
2+1i #=> (2+1i) Complex(1) #=> (1+0i) Complex(2, 3) #=> (2+3i) Complex.polar(2, 3) #=> (-1.9799849932008908+0.2822400161197344i) 3.to_c #=> (3+0i)
You can also create complex object from floating-point numbers or strings.
Complex(0.3) #=> (0.3+0i) Complex('0.3-0.5i') #=> (0.3-0.5i) Complex('2/3+3/4i') #=> ((2/3)+(3/4)*i) Complex('1@2') #=> (-0.4161468365471424+0.9092974268256817i) 0.3.to_c #=> (0.3+0i) '0.3-0.5i'.to_c #=> (0.3-0.5i) '2/3+3/4i'.to_c #=> ((2/3)+(3/4)*i) '1@2'.to_c #=> (-0.4161468365471424+0.9092974268256817i)
A complex object is either an exact or an inexact number.
Complex(1, 1) / 2 #=> ((1/2)+(1/2)*i) Complex(1, 1) / 2.0 #=> (0.5+0.5i)
BigDecimal extends the native String class to provide the to_d method.
When you require BigDecimal in your application, this method will be available on String objects.
additions to class String for Unicode normalization
A String object holds and manipulates an arbitrary sequence of bytes, typically representing characters. String objects may be created using String::new or as literals.
Because of aliasing issues, users of strings should be aware of the methods that modify the contents of a String object. Typically, methods with names ending in “!” modify their receiver, while those without a “!” return a new String. However, there are exceptions, such as String#[]=.
An Encoding instance represents a character encoding usable in Ruby. It is defined as a constant under the Encoding namespace. It has a name and optionally, aliases:
Encoding::ISO_8859_1.name #=> "ISO-8859-1" Encoding::ISO_8859_1.names #=> ["ISO-8859-1", "ISO8859-1"]
Ruby methods dealing with encodings return or accept Encoding instances as arguments (when a method accepts an Encoding instance as an argument, it can be passed an Encoding name or alias instead).
"some string".encoding #=> #<Encoding:UTF-8> string = "some string".encode(Encoding::ISO_8859_1) #=> "some string" string.encoding #=> #<Encoding:ISO-8859-1> "some string".encode "ISO-8859-1" #=> "some string"
Encoding::ASCII_8BIT is a special encoding that is usually used for a byte string, not a character string. But as the name insists, its characters in the range of ASCII are considered as ASCII characters. This is useful when you use ASCII-8BIT characters with other ASCII compatible characters.
The associated Encoding of a String can be changed in two different ways.
First, it is possible to set the Encoding of a string to a new Encoding without changing the internal byte representation of the string, with String#force_encoding. This is how you can tell Ruby the correct encoding of a string.
string #=> "R\xC3\xA9sum\xC3\xA9" string.encoding #=> #<Encoding:ISO-8859-1> string.force_encoding(Encoding::UTF_8) #=> "R\u00E9sum\u00E9"
Second, it is possible to transcode a string, i.e. translate its internal byte representation to another encoding. Its associated encoding is also set to the other encoding. See String#encode for the various forms of transcoding, and the Encoding::Converter class for additional control over the transcoding process.
string #=> "R\u00E9sum\u00E9" string.encoding #=> #<Encoding:UTF-8> string = string.encode!(Encoding::ISO_8859_1) #=> "R\xE9sum\xE9" string.encoding #=> #<Encoding::ISO-8859-1>
All Ruby script code has an associated Encoding which any String literal created in the source code will be associated to.
The default script encoding is Encoding::UTF-8 after v2.0, but it can be changed by a magic comment on the first line of the source code file (or second line, if there is a shebang line on the first). The comment must contain the word coding or encoding, followed by a colon, space and the Encoding name or alias:
# encoding: UTF-8 "some string".encoding #=> #<Encoding:UTF-8>
The __ENCODING__ keyword returns the script encoding of the file which the keyword is written:
# encoding: ISO-8859-1 __ENCODING__ #=> #<Encoding:ISO-8859-1>
ruby -K will change the default locale encoding, but this is not recommended. Ruby source files should declare its script encoding by a magic comment even when they only depend on US-ASCII strings or regular expressions.
The default encoding of the environment. Usually derived from locale.
see Encoding.locale_charmap, Encoding.find(‘locale’)
The default encoding of strings from the filesystem of the environment. This is used for strings of file names or paths.
see Encoding.find(‘filesystem’)
Each IO object has an external encoding which indicates the encoding that Ruby will use to read its data. By default Ruby sets the external encoding of an IO object to the default external encoding. The default external encoding is set by locale encoding or the interpreter -E option. Encoding.default_external returns the current value of the external encoding.
ENV["LANG"] #=> "UTF-8" Encoding.default_external #=> #<Encoding:UTF-8> $ ruby -E ISO-8859-1 -e "p Encoding.default_external" #<Encoding:ISO-8859-1> $ LANG=C ruby -e 'p Encoding.default_external' #<Encoding:US-ASCII>
The default external encoding may also be set through Encoding.default_external=, but you should not do this as strings created before and after the change will have inconsistent encodings. Instead use ruby -E to invoke ruby with the correct external encoding.
When you know that the actual encoding of the data of an IO object is not the default external encoding, you can reset its external encoding with IO#set_encoding or set it at IO object creation (see IO.new options).
To process the data of an IO object which has an encoding different from its external encoding, you can set its internal encoding. Ruby will use this internal encoding to transcode the data when it is read from the IO object.
Conversely, when data is written to the IO object it is transcoded from the internal encoding to the external encoding of the IO object.
The internal encoding of an IO object can be set with IO#set_encoding or at IO object creation (see IO.new options).
The internal encoding is optional and when not set, the Ruby default internal encoding is used. If not explicitly set this default internal encoding is nil meaning that by default, no transcoding occurs.
The default internal encoding can be set with the interpreter option -E. Encoding.default_internal returns the current internal encoding.
$ ruby -e 'p Encoding.default_internal' nil $ ruby -E ISO-8859-1:UTF-8 -e "p [Encoding.default_external, \ Encoding.default_internal]" [#<Encoding:ISO-8859-1>, #<Encoding:UTF-8>]
The default internal encoding may also be set through Encoding.default_internal=, but you should not do this as strings created before and after the change will have inconsistent encodings. Instead use ruby -E to invoke ruby with the correct internal encoding.
IO encoding example In the following example a UTF-8 encoded string “Ru00E9sumu00E9” is transcoded for output to ISO-8859-1 encoding, then read back in and transcoded to UTF-8:
string = "R\u00E9sum\u00E9" open("transcoded.txt", "w:ISO-8859-1") do |io| io.write(string) end puts "raw text:" p File.binread("transcoded.txt") puts open("transcoded.txt", "r:ISO-8859-1:UTF-8") do |io| puts "transcoded text:" p io.read end
While writing the file, the internal encoding is not specified as it is only necessary for reading. While reading the file both the internal and external encoding must be specified to obtain the correct result.
$ ruby t.rb raw text: "R\xE9sum\xE9" transcoded text: "R\u00E9sum\u00E9"
Descendants of class Exception are used to communicate between Kernel#raise and rescue statements in begin ... end blocks. Exception objects carry information about the exception – its type (the exception’s class name), an optional descriptive string, and optional traceback information. Exception subclasses may add additional information like NameError#name.
Programs may make subclasses of Exception, typically of StandardError or RuntimeError, to provide custom classes and add additional information. See the subclass list below for defaults for raise and rescue.
When an exception has been raised but not yet handled (in rescue, ensure, at_exit and END blocks) the global variable $! will contain the current exception and $@ contains the current exception’s backtrace.
It is recommended that a library should have one subclass of StandardError or RuntimeError and have specific exception types inherit from it. This allows the user to rescue a generic exception type to catch all exceptions the library may raise even if future versions of the library add new exception subclasses.
For example:
class MyLibrary class Error < RuntimeError end class WidgetError < Error end class FrobError < Error end end
To handle both WidgetError and FrobError the library user can rescue MyLibrary::Error.
The built-in subclasses of Exception are:
StandardError – default for rescue
fatal – impossible to rescue
Raised when a signal is received.
begin Process.kill('HUP',Process.pid) sleep # wait for receiver to handle signal sent by Process.kill rescue SignalException => e puts "received Exception #{e}" end
produces:
received Exception SIGHUP
The most standard error types are subclasses of StandardError. A rescue clause without an explicit Exception class will rescue all StandardErrors (and only those).
def foo raise "Oups" end foo rescue "Hello" #=> "Hello"
On the other hand:
require 'does/not/exist' rescue "Hi"
raises the exception:
LoadError: no such file to load -- does/not/exist
EncodingError is the base class for encoding errors.
BigDecimal extends the native Rational class to provide the to_d method.
When you require BigDecimal in your application, this method will be available on Rational objects.
A rational number can be represented as a paired integer number; a/b (b>0). Where a is numerator and b is denominator. Integer a equals rational a/1 mathematically.
In ruby, you can create rational object with Rational, to_r, rationalize method or suffixing r to a literal. The return values will be irreducible.
Rational(1) #=> (1/1) Rational(2, 3) #=> (2/3) Rational(4, -6) #=> (-2/3) 3.to_r #=> (3/1) 2/3r #=> (2/3)
You can also create rational object from floating-point numbers or strings.
Rational(0.3) #=> (5404319552844595/18014398509481984) Rational('0.3') #=> (3/10) Rational('2/3') #=> (2/3) 0.3.to_r #=> (5404319552844595/18014398509481984) '0.3'.to_r #=> (3/10) '2/3'.to_r #=> (2/3) 0.3.rationalize #=> (3/10)
A rational object is an exact number, which helps you to write program without any rounding errors.
10.times.inject(0){|t,| t + 0.1} #=> 0.9999999999999999 10.times.inject(0){|t,| t + Rational('0.1')} #=> (1/1)
However, when an expression has inexact factor (numerical value or operation), will produce an inexact result.
Rational(10) / 3 #=> (10/3) Rational(10) / 3.0 #=> 3.3333333333333335 Rational(-8) ** Rational(1, 3) #=> (1.0000000000000002+1.7320508075688772i)
A Struct is a convenient way to bundle a number of attributes together, using accessor methods, without having to write an explicit class.
The Struct class generates new subclasses that hold a set of members and their values. For each member a reader and writer method is created similar to Module#attr_accessor.
Customer = Struct.new(:name, :address) do def greeting "Hello #{name}!" end end dave = Customer.new("Dave", "123 Main") dave.name #=> "Dave" dave.greeting #=> "Hello Dave!"
See Struct::new for further examples of creating struct subclasses and instances.
In the method descriptions that follow a “member” parameter refers to a struct member which is either a quoted string ("name") or a Symbol (:name).
Pseudo I/O on String object.
Commonly used to simulate ‘$stdio` or `$stderr`
require 'stringio' io = StringIO.new io.puts "Hello World" io.string #=> "Hello World\n"
StringScanner provides for lexical scanning operations on a String. Here is an example of its usage:
s = StringScanner.new('This is an example string') s.eos? # -> false p s.scan(/\w+/) # -> "This" p s.scan(/\w+/) # -> nil p s.scan(/\s+/) # -> " " p s.scan(/\s+/) # -> nil p s.scan(/\w+/) # -> "is" s.eos? # -> false p s.scan(/\s+/) # -> " " p s.scan(/\w+/) # -> "an" p s.scan(/\s+/) # -> " " p s.scan(/\w+/) # -> "example" p s.scan(/\s+/) # -> " " p s.scan(/\w+/) # -> "string" s.eos? # -> true p s.scan(/\s+/) # -> nil p s.scan(/\w+/) # -> nil
Scanning a string means remembering the position of a scan pointer, which is just an index. The point of scanning is to move forward a bit at a time, so matches are sought after the scan pointer; usually immediately after it.
Given the string “test string”, here are the pertinent scan pointer positions:
t e s t s t r i n g
0 1 2 ... 1
0
When you scan for a pattern (a regular expression), the match must occur at the character after the scan pointer. If you use scan_until, then the match can occur anywhere after the scan pointer. In both cases, the scan pointer moves just beyond the last character of the match, ready to scan again from the next character onwards. This is demonstrated by the example above.
Method Categories There are other methods besides the plain scanners. You can look ahead in the string without actually scanning. You can access the most recent match. You can modify the string being scanned, reset or terminate the scanner, find out or change the position of the scan pointer, skip ahead, and so on.
beginning_of_line? (bol?)
Data There are aliases to several of the methods.
BasicObject is the parent class of all classes in Ruby. It’s an explicit blank class.
BasicObject can be used for creating object hierarchies independent of Ruby’s object hierarchy, proxy objects like the Delegator class, or other uses where namespace pollution from Ruby’s methods and classes must be avoided.
To avoid polluting BasicObject for other users an appropriately named subclass of BasicObject should be created instead of directly modifying BasicObject:
class MyObjectSystem < BasicObject end
BasicObject does not include Kernel (for methods like puts) and BasicObject is outside of the namespace of the standard library so common classes will not be found without using a full class path.
A variety of strategies can be used to provide useful portions of the standard library to subclasses of BasicObject. A subclass could include Kernel to obtain puts, exit, etc. A custom Kernel-like module could be created and included or delegation can be used via method_missing:
class MyObjectSystem < BasicObject DELEGATE = [:puts, :p] def method_missing(name, *args, &block) super unless DELEGATE.include? name ::Kernel.send(name, *args, &block) end def respond_to_missing?(name, include_private = false) DELEGATE.include?(name) or super end end
Access to classes and modules from the Ruby standard library can be obtained in a BasicObject subclass by referencing the desired constant from the root like ::File or ::Enumerator. Like method_missing, const_missing can be used to delegate constant lookup to Object:
class MyObjectSystem < BasicObject def self.const_missing(name) ::Object.const_get(name) end end
The GetoptLong class allows you to parse command line options similarly to the GNU getopt_long() C library call. Note, however, that GetoptLong is a pure Ruby implementation.
GetoptLong allows for POSIX-style options like --file as well as single letter options like -f
The empty option -- (two minus symbols) is used to end option processing. This can be particularly important if options have optional arguments.
Here is a simple example of usage:
require 'getoptlong' opts = GetoptLong.new( [ '--help', '-h', GetoptLong::NO_ARGUMENT ], [ '--repeat', '-n', GetoptLong::REQUIRED_ARGUMENT ], [ '--name', GetoptLong::OPTIONAL_ARGUMENT ] ) dir = nil name = nil repetitions = 1 opts.each do |opt, arg| case opt when '--help' puts <<-EOF hello [OPTION] ... DIR -h, --help: show help --repeat x, -n x: repeat x times --name [name]: greet user by name, if name not supplied default is John DIR: The directory in which to issue the greeting. EOF when '--repeat' repetitions = arg.to_i when '--name' if arg == '' name = 'John' else name = arg end end end if ARGV.length != 1 puts "Missing dir argument (try --help)" exit 0 end dir = ARGV.shift Dir.chdir(dir) for i in (1..repetitions) print "Hello" if name print ", #{name}" end puts end
Example command line:
hello -n 6 --name -- /tmp
A class that provides two-phase lock with a counter. See Sync_m for details.
Raised when attempting to divide an integer by 0.
42 / 0 #=> ZeroDivisionError: divided by 0
Note that only division by an exact 0 will raise the exception:
42 / 0.0 #=> Float::INFINITY 42 / -0.0 #=> -Float::INFINITY 0 / 0.0 #=> NaN