class Resolv

Resolv is a thread-aware DNS resolver library written in Ruby. Resolv can handle multiple DNS requests concurrently without blocking the entire Ruby interpreter.

See also resolv-replace.rb to replace the libc resolver with Resolv.

Resolv can look up various DNS resources using the DNS module directly.

Examples:

p Resolv.getaddress "www.ruby-lang.org"
p Resolv.getname "210.251.121.214"

Resolv::DNS.open do |dns|
  ress = dns.getresources "www.ruby-lang.org", Resolv::DNS::Resource::IN::A
  p ress.map(&:address)
  ress = dns.getresources "ruby-lang.org", Resolv::DNS::Resource::IN::MX
  p ress.map { |r| [r.exchange.to_s, r.preference] }
end

Bugs ↑

  • NIS is not supported.

  • /etc/nsswitch.conf is not supported.

Constants

AddressRegex

Address Regexp to use for matching IP addresses.

DefaultResolver

Default resolver to use for Resolv class methods.

VERSION

Public Class Methods

each_address (name, &block)

Iterates over all IP addresses for name.

# File lib/resolv.rb, line 55
def self.each_address(name, &block)
  DefaultResolver.each_address(name, &block)
end
each_name (address, &proc)

Iterates over all hostnames for address.

# File lib/resolv.rb, line 76
def self.each_name(address, &proc)
  DefaultResolver.each_name(address, &proc)
end
getaddress (name)

Looks up the first IP address for name.

# File lib/resolv.rb, line 41
def self.getaddress(name)
  DefaultResolver.getaddress(name)
end
getaddresses (name)

Looks up all IP address for name.

# File lib/resolv.rb, line 48
def self.getaddresses(name)
  DefaultResolver.getaddresses(name)
end
getname (address)

Looks up the hostname of address.

# File lib/resolv.rb, line 62
def self.getname(address)
  DefaultResolver.getname(address)
end
getnames (address)

Looks up all hostnames for address.

# File lib/resolv.rb, line 69
def self.getnames(address)
  DefaultResolver.getnames(address)
end
new (resolvers=(arg_not_set = true; nil), use_ipv6: (keyword_not_set = true; nil))

Creates a new Resolv using resolvers.

If resolvers is not given, a hash, or nil, uses a Hosts resolver and and a DNS resolver. If resolvers is a hash, uses the hash as configuration for the DNS resolver.

# File lib/resolv.rb, line 87
def initialize(resolvers=(arg_not_set = true; nil), use_ipv6: (keyword_not_set = true; nil))
  if !keyword_not_set && !arg_not_set
    warn "Support for separate use_ipv6 keyword is deprecated, as it is ignored if an argument is provided. Do not provide a positional argument if using the use_ipv6 keyword argument.", uplevel: 1
  end

  @resolvers = case resolvers
  when Hash, nil
    [Hosts.new, DNS.new(DNS::Config.default_config_hash.merge(resolvers || {}))]
  else
    resolvers
  end
end

Public Instance Methods

each_address (name) { |name| ... }

Iterates over all IP addresses for name.

# File lib/resolv.rb, line 120
def each_address(name)
  if AddressRegex =~ name
    yield name
    return
  end
  yielded = false
  @resolvers.each {|r|
    r.each_address(name) {|address|
      yield address.to_s
      yielded = true
    }
    return if yielded
  }
end
each_name (address) { |name| ... }

Iterates over all hostnames for address.

# File lib/resolv.rb, line 155
def each_name(address)
  yielded = false
  @resolvers.each {|r|
    r.each_name(address) {|name|
      yield name.to_s
      yielded = true
    }
    return if yielded
  }
end
getaddress (name)

Looks up the first IP address for name.

# File lib/resolv.rb, line 103
def getaddress(name)
  each_address(name) {|address| return address}
  raise ResolvError.new("no address for #{name}")
end
getaddresses (name)

Looks up all IP address for name.

# File lib/resolv.rb, line 111
def getaddresses(name)
  ret = []
  each_address(name) {|address| ret << address}
  return ret
end
getname (address)

Looks up the hostname of address.

# File lib/resolv.rb, line 138
def getname(address)
  each_name(address) {|name| return name}
  raise ResolvError.new("no name for #{address}")
end
getnames (address)

Looks up all hostnames for address.

# File lib/resolv.rb, line 146
def getnames(address)
  ret = []
  each_name(address) {|name| ret << name}
  return ret
end