Results for: "OptionParser"

Exception

Class Exception and its subclasses are used to communicate between Kernel#raise and rescue statements in begin ... end blocks.

An Exception object carries information about an exception:

Its type (the exception’s class).
An optional descriptive message.
Optional backtrace information.

Some built-in subclasses of Exception have additional methods: e.g., NameError#name.

Defaults

Two Ruby statements have default exception classes:

raise: defaults to RuntimeError.
rescue: defaults to StandardError.

Global Variables

When an exception has been raised but not yet handled (in rescue, ensure, at_exit and END blocks), two global variables are set:

$! contains the current exception.
$@ contains its backtrace.

Custom Exceptions

To provide additional or alternate information, a program may create custom exception classes that derive from the built-in exception classes.

A good practice is for a library to create a single “generic” exception class (typically a subclass of StandardError or RuntimeError) and have its other exception classes derive from that class. This allows the user to rescue the generic exception, thus catching all exceptions the library may raise even if future versions of the library add new exception subclasses.

For example:

class MyLibrary
  class Error < ::StandardError
  end

  class WidgetError < Error
  end

  class FrobError < Error
  end

end

To handle both MyLibrary::WidgetError and MyLibrary::FrobError the library user can rescue MyLibrary::Error.

Built-In `Exception` Classes

The built-in subclasses of Exception are:

SignalException

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

ZeroDivisionError

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

NoMatchingPatternError

No documentation available

NoMatchingPatternKeyError

No documentation available

Rational

A rational number can be represented as a pair of integer numbers: a/b (b>0), where a is the numerator and b is the denominator. Integer a equals rational a/1 mathematically.

You can create a Rational object explicitly with:

A rational literal.

You can convert certain objects to Rationals with:

Method Rational.

Examples

Rational(1)      #=> (1/1)
Rational(2, 3)   #=> (2/3)
Rational(4, -6)  #=> (-2/3) # Reduced.
3.to_r           #=> (3/1)
2/3r             #=> (2/3)

You can also create rational objects 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 programs 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 includes an inexact component (numerical value or operation), it 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)

TCPServer

TCPServer represents a TCP/IP server socket.

A simple TCP server may look like:

require 'socket'

server = TCPServer.new 2000 # Server bind to port 2000
loop do
  client = server.accept    # Wait for a client to connect
  client.puts "Hello !"
  client.puts "Time is #{Time.now}"
  client.close
end

A more usable server (serving multiple clients):

require 'socket'

server = TCPServer.new 2000
loop do
  Thread.start(server.accept) do |client|
    client.puts "Hello !"
    client.puts "Time is #{Time.now}"
    client.close
  end
end

UNIXServer

UNIXServer represents a UNIX domain stream server socket.

WIN32OLERuntimeError

Raised when OLE processing failed.

EX:

obj = WIN32OLE.new("NonExistProgID")

raises the exception:

WIN32OLERuntimeError: unknown OLE server: `NonExistProgID'
    HRESULT error code:0x800401f3
      Invalid class string

WIN32OLEQueryInterfaceError

No documentation available

GetoptLong

Class GetoptLong provides parsing both for options and for regular arguments.

Using GetoptLong, you can define options for your program. The program can then capture and respond to whatever options are included in the command that executes the program.

A simple example: file simple.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--number', '-n', GetoptLong::REQUIRED_ARGUMENT],
  ['--verbose', '-v', GetoptLong::OPTIONAL_ARGUMENT],
  ['--help', '-h', GetoptLong::NO_ARGUMENT]
)

If you are somewhat familiar with options, you may want to skip to this full example.

Options

A GetoptLong option has:

A string option name.
Zero or more string aliases for the name.
An option type.

Options may be defined by calling singleton method GetoptLong.new, which returns a new GetoptLong object. Options may then be processed by calling other methods such as GetoptLong#each.

Option Name and Aliases

In the array that defines an option, the first element is the string option name. Often the name takes the ‘long’ form, beginning with two hyphens.

The option name may have any number of aliases, which are defined by additional string elements.

The name and each alias must be of one of two forms:

Two hyphens, followed by one or more letters.
One hyphen, followed by a single letter.

File aliases.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', '-x', '--aaa', '-a', '-p', GetoptLong::NO_ARGUMENT]
)
options.each do |option, argument|
  p [option, argument]
end

An option may be cited by its name, or by any of its aliases; the parsed option always reports the name, not an alias:

$ ruby aliases.rb -a -p --xxx --aaa -x

Output:

["--xxx", ""]
["--xxx", ""]
["--xxx", ""]
["--xxx", ""]
["--xxx", ""]

An option may also be cited by an abbreviation of its name or any alias, as long as that abbreviation is unique among the options.

File abbrev.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', GetoptLong::NO_ARGUMENT],
  ['--xyz', GetoptLong::NO_ARGUMENT]
)
options.each do |option, argument|
  p [option, argument]
end

Command line:

$ ruby abbrev.rb --xxx --xx --xyz --xy

Output:

["--xxx", ""]
["--xxx", ""]
["--xyz", ""]
["--xyz", ""]

This command line raises GetoptLong::AmbiguousOption:

$ ruby abbrev.rb --x

Repetition

An option may be cited more than once:

$ ruby abbrev.rb --xxx --xyz --xxx --xyz

Output:

["--xxx", ""]
["--xyz", ""]
["--xxx", ""]
["--xyz", ""]

Treating Remaining Options as Arguments

A option-like token that appears anywhere after the token -- is treated as an ordinary argument, and is not processed as an option:

$ ruby abbrev.rb --xxx --xyz -- --xxx --xyz

Output:

["--xxx", ""]
["--xyz", ""]

Option Types

Each option definition includes an option type, which controls whether the option takes an argument.

File types.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', GetoptLong::REQUIRED_ARGUMENT],
  ['--yyy', GetoptLong::OPTIONAL_ARGUMENT],
  ['--zzz', GetoptLong::NO_ARGUMENT]
)
options.each do |option, argument|
  p [option, argument]
end

Note that an option type has to do with the option argument (whether it is required, optional, or forbidden), not with whether the option itself is required.

Option with Required Argument

An option of type GetoptLong::REQUIRED_ARGUMENT must be followed by an argument, which is associated with that option:

$ ruby types.rb --xxx foo

Output:

["--xxx", "foo"]

If the option is not last, its argument is whatever follows it (even if the argument looks like another option):

$ ruby types.rb --xxx --yyy

Output:

["--xxx", "--yyy"]

If the option is last, an exception is raised:

$ ruby types.rb
# Raises GetoptLong::MissingArgument

Option with Optional Argument

An option of type GetoptLong::OPTIONAL_ARGUMENT may be followed by an argument, which if given is associated with that option.

If the option is last, it does not have an argument:

$ ruby types.rb --yyy

Output:

["--yyy", ""]

If the option is followed by another option, it does not have an argument:

$ ruby types.rb --yyy --zzz

Output:

["--yyy", ""]
["--zzz", ""]

Otherwise the option is followed by its argument, which is associated with that option:

$ ruby types.rb --yyy foo

Output:

["--yyy", "foo"]

Option with No Argument

An option of type GetoptLong::NO_ARGUMENT takes no argument:

ruby types.rb --zzz foo

Output:

["--zzz", ""]

ARGV

You can process options either with method each and a block, or with method get.

During processing, each found option is removed, along with its argument if there is one. After processing, each remaining element was neither an option nor the argument for an option.

File argv.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', GetoptLong::REQUIRED_ARGUMENT],
  ['--yyy', GetoptLong::OPTIONAL_ARGUMENT],
  ['--zzz', GetoptLong::NO_ARGUMENT]
)
puts "Original ARGV: #{ARGV}"
options.each do |option, argument|
  p [option, argument]
end
puts "Remaining ARGV: #{ARGV}"

Command line:

$ ruby argv.rb --xxx Foo --yyy Bar Baz --zzz Bat Bam

Output:

Original ARGV: ["--xxx", "Foo", "--yyy", "Bar", "Baz", "--zzz", "Bat", "Bam"]
["--xxx", "Foo"]
["--yyy", "Bar"]
["--zzz", ""]
Remaining ARGV: ["Baz", "Bat", "Bam"]

Ordering

There are three settings that control the way the options are interpreted:

PERMUTE.
REQUIRE_ORDER.
RETURN_IN_ORDER.

The initial setting for a new GetoptLong object is REQUIRE_ORDER if environment variable POSIXLY_CORRECT is defined, PERMUTE otherwise.

PERMUTE Ordering

In the PERMUTE ordering, options and other, non-option, arguments may appear in any order and any mixture.

File permute.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', GetoptLong::REQUIRED_ARGUMENT],
  ['--yyy', GetoptLong::OPTIONAL_ARGUMENT],
  ['--zzz', GetoptLong::NO_ARGUMENT]
)
puts "Original ARGV: #{ARGV}"
options.each do |option, argument|
  p [option, argument]
end
puts "Remaining ARGV: #{ARGV}"

Command line:

$ ruby permute.rb Foo --zzz Bar --xxx Baz --yyy Bat Bam --xxx Bag Bah

Output:

Original ARGV: ["Foo", "--zzz", "Bar", "--xxx", "Baz", "--yyy", "Bat", "Bam", "--xxx", "Bag", "Bah"]
["--zzz", ""]
["--xxx", "Baz"]
["--yyy", "Bat"]
["--xxx", "Bag"]
Remaining ARGV: ["Foo", "Bar", "Bam", "Bah"]

REQUIRE_ORDER Ordering

In the REQUIRE_ORDER ordering, all options precede all non-options; that is, each word after the first non-option word is treated as a non-option word (even if it begins with a hyphen).

File require_order.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', GetoptLong::REQUIRED_ARGUMENT],
  ['--yyy', GetoptLong::OPTIONAL_ARGUMENT],
  ['--zzz', GetoptLong::NO_ARGUMENT]
)
options.ordering = GetoptLong::REQUIRE_ORDER
puts "Original ARGV: #{ARGV}"
options.each do |option, argument|
  p [option, argument]
end
puts "Remaining ARGV: #{ARGV}"

Command line:

$ ruby require_order.rb --xxx Foo Bar --xxx Baz --yyy Bat -zzz

Output:

Original ARGV: ["--xxx", "Foo", "Bar", "--xxx", "Baz", "--yyy", "Bat", "-zzz"]
["--xxx", "Foo"]
Remaining ARGV: ["Bar", "--xxx", "Baz", "--yyy", "Bat", "-zzz"]

RETURN_IN_ORDER Ordering

In the RETURN_IN_ORDER ordering, every word is treated as an option. A word that begins with a hyphen (or two) is treated in the usual way; a word word that does not so begin is treated as an option whose name is an empty string, and whose value is word.

File return_in_order.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--xxx', GetoptLong::REQUIRED_ARGUMENT],
  ['--yyy', GetoptLong::OPTIONAL_ARGUMENT],
  ['--zzz', GetoptLong::NO_ARGUMENT]
)
options.ordering = GetoptLong::RETURN_IN_ORDER
puts "Original ARGV: #{ARGV}"
options.each do |option, argument|
  p [option, argument]
end
puts "Remaining ARGV: #{ARGV}"

Command line:

$ ruby return_in_order.rb Foo --xxx Bar Baz --zzz Bat Bam

Output:

Original ARGV: ["Foo", "--xxx", "Bar", "Baz", "--zzz", "Bat", "Bam"]
["", "Foo"]
["--xxx", "Bar"]
["", "Baz"]
["--zzz", ""]
["", "Bat"]
["", "Bam"]
Remaining ARGV: []

Full Example

File fibonacci.rb:

require 'getoptlong'

options = GetoptLong.new(
  ['--number', '-n', GetoptLong::REQUIRED_ARGUMENT],
  ['--verbose', '-v', GetoptLong::OPTIONAL_ARGUMENT],
  ['--help', '-h', GetoptLong::NO_ARGUMENT]
)

def help(status = 0)
  puts <<~HELP
    Usage:

      -n n, --number n:
        Compute Fibonacci number for n.
      -v [boolean], --verbose [boolean]:
        Show intermediate results; default is 'false'.
      -h, --help:
        Show this help.
  HELP
  exit(status)
end

def print_fibonacci (number)
  return 0 if number == 0
  return 1 if number == 1 or number == 2
  i = 0
  j = 1
  (2..number).each do
    k = i + j
    i = j
    j = k
    puts j if @verbose
  end
  puts j unless @verbose
end

options.each do |option, argument|
  case option
  when '--number'
    @number = argument.to_i
  when '--verbose'
    @verbose = if argument.empty?
      true
    elsif argument.match(/true/i)
      true
    elsif argument.match(/false/i)
      false
    else
      puts '--verbose argument must be true or false'
      help(255)
    end
  when '--help'
    help
  end
end

unless @number
  puts 'Option --number is required.'
  help(255)
end

print_fibonacci(@number)

Command line:

$ ruby fibonacci.rb

Output:

Option --number is required.
Usage:

  -n n, --number n:
    Compute Fibonacci number for n.
  -v [boolean], --verbose [boolean]:
    Show intermediate results; default is 'false'.
  -h, --help:
    Show this help.

Command line:

$ ruby fibonacci.rb --number

Raises GetoptLong::MissingArgument:

fibonacci.rb: option `--number' requires an argument

Command line:

$ ruby fibonacci.rb --number 6

Output:

Command line:

$ ruby fibonacci.rb --number 6 --verbose

Output:

Command line:

$ ruby fibonacci.rb –number 6 –verbose yes

Output:

--verbose argument must be true or false
Usage:

  -n n, --number n:
    Compute Fibonacci number for n.
  -v [boolean], --verbose [boolean]:
    Show intermediate results; default is 'false'.
  -h, --help:
    Show this help.

FiberError

Raised when an invalid operation is attempted on a Fiber, in particular when attempting to call/resume a dead fiber, attempting to yield from the root fiber, or calling a fiber across threads.

fiber = Fiber.new{}
fiber.resume #=> nil
fiber.resume #=> FiberError: dead fiber called

Interrupt

Raised when the interrupt signal is received, typically because the user has pressed Control-C (on most posix platforms). As such, it is a subclass of SignalException.

begin
  puts "Press ctrl-C when you get bored"
  loop {}
rescue Interrupt => e
  puts "Note: You will typically use Signal.trap instead."
end

produces:

Press ctrl-C when you get bored

then waits until it is interrupted with Control-C and then prints:

Note: You will typically use Signal.trap instead.

StandardError

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

ArgumentError

Raised when the arguments are wrong and there isn’t a more specific Exception class.

Ex: passing the wrong number of arguments

[1, 2, 3].first(4, 5)

raises the exception:

ArgumentError: wrong number of arguments (given 2, expected 1)

Ex: passing an argument that is not acceptable:

[1, 2, 3].first(-4)

raises the exception:

ArgumentError: negative array size

ScriptError

ScriptError is the superclass for errors raised when a script can not be executed because of a LoadError, NotImplementedError or a SyntaxError. Note these type of ScriptErrors are not StandardError and will not be rescued unless it is specified explicitly (or its ancestor Exception).

NotImplementedError

Raised when a feature is not implemented on the current platform. For example, methods depending on the fsync or fork system calls may raise this exception if the underlying operating system or Ruby runtime does not support them.

Note that if fork raises a NotImplementedError, then respond_to?(:fork) returns false.

RuntimeError

A generic error class raised when an invalid operation is attempted. Kernel#raise will raise a RuntimeError if no Exception class is specified.

raise "ouch"

raises the exception:

RuntimeError: ouch

SecurityError

No longer used by internal code.

OLEProperty

OLEProperty helper class of Property with arguments.

IOError

Raised when an IO operation fails.

File.open("/etc/hosts") {|f| f << "example"}
  #=> IOError: not opened for writing

File.open("/etc/hosts") {|f| f.close; f.read }
  #=> IOError: closed stream

Note that some IO failures raise SystemCallErrors and these are not subclasses of IOError:

File.open("does/not/exist")
  #=> Errno::ENOENT: No such file or directory - does/not/exist

ClosedQueueError

The exception class which will be raised when pushing into a closed Queue. See Thread::Queue#close and Thread::SizedQueue#close.

Comparable

The Comparable mixin is used by classes whose objects may be ordered. The class must define the <=> operator, which compares the receiver against another object, returning a value less than 0, returning 0, or returning a value greater than 0, depending on whether the receiver is less than, equal to, or greater than the other object. If the other object is not comparable then the <=> operator should return nil. Comparable uses <=> to implement the conventional comparison operators (<, <=, ==, >=, and >) and the method between?.

class SizeMatters
  include Comparable
  attr :str
  def <=>(other)
    str.size <=> other.str.size
  end
  def initialize(str)
    @str = str
  end
  def inspect
    @str
  end
end

s1 = SizeMatters.new("Z")
s2 = SizeMatters.new("YY")
s3 = SizeMatters.new("XXX")
s4 = SizeMatters.new("WWWW")
s5 = SizeMatters.new("VVVVV")

s1 < s2                       #=> true
s4.between?(s1, s3)           #=> false
s4.between?(s3, s5)           #=> true
[ s3, s2, s5, s4, s1 ].sort   #=> [Z, YY, XXX, WWWW, VVVVV]

What’s Here

Module Comparable provides these methods, all of which use method <=>:

<: Returns whether self is less than the given object.
<=: Returns whether self is less than or equal to the given object.
==: Returns whether self is equal to the given object.
>: Returns whether self is greater than or equal to the given object.
>=: Returns whether self is greater than the given object.
between?: Returns true if self is between two given objects.
clamp: For given objects min and max, or range (min..max), returns:
- min if (self <=> min) < 0.
- max if (self <=> max) > 0.
- self otherwise.

Observable

The Observer pattern (also known as publish/subscribe) provides a simple mechanism for one object to inform a set of interested third-party objects when its state changes.

Mechanism

The notifying class mixes in the Observable module, which provides the methods for managing the associated observer objects.

The observable object must:

assert that it has #changed
call #notify_observers

An observer subscribes to updates using Observable#add_observer, which also specifies the method called via notify_observers. The default method for notify_observers is update.

Example

The following example demonstrates this nicely. A Ticker, when run, continually receives the stock Price for its @symbol. A Warner is a general observer of the price, and two warners are demonstrated, a WarnLow and a WarnHigh, which print a warning if the price is below or above their set limits, respectively.

The update callback allows the warners to run without being explicitly called. The system is set up with the Ticker and several observers, and the observers do their duty without the top-level code having to interfere.

Note that the contract between publisher and subscriber (observable and observer) is not declared or enforced. The Ticker publishes a time and a price, and the warners receive that. But if you don’t ensure that your contracts are correct, nothing else can warn you.

require "observer"

class Ticker          ### Periodically fetch a stock price.
  include Observable

  def initialize(symbol)
    @symbol = symbol
  end

  def run
    last_price = nil
    loop do
      price = Price.fetch(@symbol)
      print "Current price: #{price}\n"
      if price != last_price
        changed                 # notify observers
        last_price = price
        notify_observers(Time.now, price)
      end
      sleep 1
    end
  end
end

class Price           ### A mock class to fetch a stock price (60 - 140).
  def self.fetch(symbol)
    60 + rand(80)
  end
end

class Warner          ### An abstract observer of Ticker objects.
  def initialize(ticker, limit)
    @limit = limit
    ticker.add_observer(self)
  end
end

class WarnLow < Warner
  def update(time, price)       # callback for observer
    if price < @limit
      print "--- #{time.to_s}: Price below #@limit: #{price}\n"
    end
  end
end

class WarnHigh < Warner
  def update(time, price)       # callback for observer
    if price > @limit
      print "+++ #{time.to_s}: Price above #@limit: #{price}\n"
    end
  end
end

ticker = Ticker.new("MSFT")
WarnLow.new(ticker, 80)
WarnHigh.new(ticker, 120)
ticker.run

Produces:

Current price: 83
Current price: 75
--- Sun Jun 09 00:10:25 CDT 2002: Price below 80: 75
Current price: 90
Current price: 134
+++ Sun Jun 09 00:10:25 CDT 2002: Price above 120: 134
Current price: 134
Current price: 112
Current price: 79
--- Sun Jun 09 00:10:25 CDT 2002: Price below 80: 79

Usage with procs

The #notify_observers method can also be used with +proc+s by using the :call as func parameter.

The following example illustrates the use of a lambda:

require 'observer'

class Ticker
  include Observable

  def run
    # logic to retrieve the price (here 77.0)
    changed
    notify_observers(77.0)
  end
end

ticker = Ticker.new
warner = ->(price) { puts "New price received: #{price}" }
ticker.add_observer(warner, :call)
ticker.run

CoreExtensions

No documentation available

Results for: "OptionParser"

Defaults

Global Variables

Custom Exceptions

Built-In Exception Classes

Options

Option Name and Aliases

Repetition

Treating Remaining Options as Arguments

Option Types

Option with Required Argument

Option with Optional Argument

Option with No Argument

ARGV

Ordering

PERMUTE Ordering

REQUIRE_ORDER Ordering

RETURN_IN_ORDER Ordering

Full Example

What’s Here

Mechanism

Example

Usage with procs

Built-In `Exception` Classes