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

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]

fileutils.rb

Copyright © 2000-2007 Minero Aoki

This program is free software. You can distribute/modify this program under the same terms of ruby.

module FileUtils

Namespace for several file utility methods for copying, moving, removing, etc.

Module Functions

require 'fileutils'

FileUtils.cd(dir, **options)
FileUtils.cd(dir, **options) {|dir| block }
FileUtils.pwd()
FileUtils.mkdir(dir, **options)
FileUtils.mkdir(list, **options)
FileUtils.mkdir_p(dir, **options)
FileUtils.mkdir_p(list, **options)
FileUtils.rmdir(dir, **options)
FileUtils.rmdir(list, **options)
FileUtils.ln(target, link, **options)
FileUtils.ln(targets, dir, **options)
FileUtils.ln_s(target, link, **options)
FileUtils.ln_s(targets, dir, **options)
FileUtils.ln_sf(target, link, **options)
FileUtils.cp(src, dest, **options)
FileUtils.cp(list, dir, **options)
FileUtils.cp_r(src, dest, **options)
FileUtils.cp_r(list, dir, **options)
FileUtils.mv(src, dest, **options)
FileUtils.mv(list, dir, **options)
FileUtils.rm(list, **options)
FileUtils.rm_r(list, **options)
FileUtils.rm_rf(list, **options)
FileUtils.install(src, dest, **options)
FileUtils.chmod(mode, list, **options)
FileUtils.chmod_R(mode, list, **options)
FileUtils.chown(user, group, list, **options)
FileUtils.chown_R(user, group, list, **options)
FileUtils.touch(list, **options)

Possible options are:

:force

forced operation (rewrite files if exist, remove directories if not empty, etc.);

:verbose

print command to be run, in bash syntax, before performing it;

:preserve

preserve object’s group, user and modification time on copying;

:noop

no changes are made (usable in combination with :verbose which will print the command to run)

Each method documents the options that it honours. See also ::commands, ::options and ::options_of methods to introspect which command have which options.

All methods that have the concept of a “source” file or directory can take either one file or a list of files in that argument. See the method documentation for examples.

There are some ‘low level’ methods, which do not accept keyword arguments:

FileUtils.copy_entry(src, dest, preserve = false, dereference_root = false, remove_destination = false)
FileUtils.copy_file(src, dest, preserve = false, dereference = true)
FileUtils.copy_stream(srcstream, deststream)
FileUtils.remove_entry(path, force = false)
FileUtils.remove_entry_secure(path, force = false)
FileUtils.remove_file(path, force = false)
FileUtils.compare_file(path_a, path_b)
FileUtils.compare_stream(stream_a, stream_b)
FileUtils.uptodate?(file, cmp_list)

module FileUtils::Verbose

This module has all methods of FileUtils module, but it outputs messages before acting. This equates to passing the :verbose flag to methods in FileUtils.

module FileUtils::NoWrite

This module has all methods of FileUtils module, but never changes files/directories. This equates to passing the :noop flag to methods in FileUtils.

module FileUtils::DryRun

This module has all methods of FileUtils module, but never changes files/directories. This equates to passing the :noop and :verbose flags to methods in FileUtils.

Timeout long-running blocks

Synopsis

require 'timeout'
status = Timeout::timeout(5) {
  # Something that should be interrupted if it takes more than 5 seconds...
}

Description

Timeout provides a way to auto-terminate a potentially long-running operation if it hasn’t finished in a fixed amount of time.

Previous versions didn’t use a module for namespacing, however timeout is provided for backwards compatibility. You should prefer Timeout.timeout instead.

Copyright

Copyright

© 2000 Network Applied Communication Laboratory, Inc.

Copyright

© 2000 Information-technology Promotion Agency, Japan

Potentially raised when a specification is validated.

FIXME: This isn’t documented in Nutshell.

Since MonitorMixin.new_cond returns a ConditionVariable, and the example above calls while_wait and signal, this class should be documented.

POP3 authentication error.

Represents an SMTP authentication error.

Raised when attempting to uninstall a gem that isn’t in GEM_HOME.

Mixin methods for –version and –platform Gem::Command options.

A pointer to a C union

Eigenvalues and eigenvectors of a real matrix.

Computes the eigenvalues and eigenvectors of a matrix A.

If A is diagonalizable, this provides matrices V and D such that A = V*D*V.inv, where D is the diagonal matrix with entries equal to the eigenvalues and V is formed by the eigenvectors.

If A is symmetric, then V is orthogonal and thus A = V*D*V.t