How to get my machine's IP address from Ruby without leveraging from other IP address?

Question

I have searched everywhere but their solution requires some form of IP address. Here are the solutions i have found.

    require 'socket'
#METHOD 1
    ip = IPSocket.getaddress(Socket.gethostname)
    puts ip 

#METHOD 2
    host = Socket.gethostname
    puts host

#METHOD 3(uses Google's address)
    ip = UDPSocket.open {|s| s.connect("64.233.187.99", 1); s.addr.last}
    puts ip

#METHOD 4(uses gateway address)
    def local_ip
      orig, Socket.do_not_reverse_lookup = Socket.do_not_reverse_lookup, true  # turn off reverse DNS resolution temporarily

      UDPSocket.open do |s|
        s.connect '192.168.1.1', 1
        s.addr.last
      end
    ensure
      Socket.do_not_reverse_lookup = orig
    end

    ip=local_ip
    puts ip

All of them require IP address of someone. Is there a solution that does not use someone else's IP address? Preferably, platform independent.

What "IP address of someone" does the first one require? Also, who said that gateways are always at 192.168.1.1 — Matti Virkkunen, Jan 01 '13 at 18:17
@EvgeniyRyzhkov: Verbatim from the docs (http://docs.python.org/2/library/socket.html): "*... If you want to know the current machine’s IP address, you may want to use gethostbyname(gethostname()). This operation assumes that there is a valid address-to-host mapping for the host, and the assumption does not always hold.*". Please note the **last seven words**. — alk, Jan 01 '13 at 19:01
UDPSocket.connect(someone else's IP) doesn't actually connect, UDP being famously connectionless. So the use of someone else's IP, while inelegant, is functionally harmless. Well, elegance has a value, but using 0.0.0.0 or 127.0.0.1, as suggested by some answers at https://superuser.com/questions/698244/ip-address-that-is-the-equivalent-of-dev-null, doesn't work here. — Martin Dorey, Apr 06 '17 at 16:54

Itay Grudev · Answer 1 · 2020-06-11T05:57:51.513

49

Isn't the solution you are looking for just:

require 'socket'

addr_infos = Socket.ip_address_list

Since a machine can have multiple interfaces and multiple IP Addresses, this method returns an array of Addrinfo.

You can fetch the exact IP addresses like this:

addr_infos.each do |addr_info|
  puts addr_info.ip_address
end

You can further filter the list by rejecting loopback and private addresses, as they are usually not what you're interested in, like so:

addr_infos.reject( &:ipv4_loopback? )
          .reject( &:ipv6_loopback? )
          .reject( &:ipv4_private? )

edited Jun 11 '20 at 05:57

answered Dec 13 '14 at 00:21

Itay Grudev

7,055
4
54
86

2

Yup, this is exactly what I needed. :) – Piotrek Okoński Dec 23 '14 at 09:12
1

Ruby 1.8.7's Socket doesn't have ip_address_list(). I too wish I didn't have to care. – Martin Dorey Apr 06 '17 at 16:47
@MartinDorey :D My condolences. But you can still use [Eugene Rourke's solution](http://stackoverflow.com/a/14113251/894209). – Itay Grudev Apr 06 '17 at 22:04

score 31 · Answer 2 · edited Aug 19 '19 at 08:00

31

This is what I've been using in production for years:

require 'socket'
ip = Socket.ip_address_list.detect{|intf| intf.ipv4_private?}
ip.ip_address

Works great; tested on aws and classical hosting

edited Aug 19 '19 at 08:00

yegor256

102,010
123
446
597

answered Sep 07 '16 at 10:19

fuzzygroup

1,109
12
12

appears it uses getifaddrs under the covers, FWIW. See also http://stackoverflow.com/a/7809076/32453 if you are looking for a public ipv4 – rogerdpack Feb 24 '17 at 18:37

Eugene Rourke · Answer 3 · 2013-01-01T19:02:37.650

16

require 'socket'
Socket::getaddrinfo(Socket.gethostname,"echo",Socket::AF_INET)[0][3]

quite like method 1, actually

edited Jan 01 '13 at 19:02

answered Jan 01 '13 at 18:53

Eugene Rourke

4,934
1
22
24

Please see my comment on the OP, regarding the use of `gethostname()`. – alk Jan 01 '13 at 19:18

score 1 · Answer 4 · answered Jan 01 '13 at 19:26

As there is no such thing as a default ip-interface to a host (there does not need to be any ip-interface at all actually) all assumptions regarding nameing are vague, do not necessarily hold.

The value returned by gethostname() can be defined independently to any ip-setup, so it does not need to reflect a valid host in terms of a hostname which could be resolved to any ip-address.

From the POSIX system's API's view the only reliabe function to test for the availablily of (ip-)interfaces is the function getifaddrs(), which returns a list of all interfaces along with their parameters.

As it looks as if Ruby's current Socket lib does not provide an interface to it, this (http://rubygems.org/gems/system-getifaddrs) gem based approach does seem to be the only way to go.

Socket.ip_address_list seems to use getifaddrs (though it might be recent since this answer was posted) FWIW. — rogerdpack, Feb 24 '17 at 18:40
Actually, a routing table can, and often does, specify a default interface. — Thayne, Jun 12 '17 at 21:28

score 0 · Answer 5 · edited May 23 '17 at 12:18

0

parse the output of the ip command?

from https://gist.github.com/henriquemenezes/a99f13da957515023e78aea30d6c0a48

gw = `ip route show`[/default.*/][/\d+\.\d+\.\d+\.\d+/]

or parse the output of the ipconfig command: https://stackoverflow.com/a/12632929/32453

edited May 23 '17 at 12:18

Community

1
1

answered Feb 24 '17 at 18:31

rogerdpack

62,887
36
269
388

1

Won't that give you the ip address of the gateway for the default interface, not the ip address of the default interface? – Thayne Jun 12 '17 at 21:26
man, what did you paste? This is the default GW, and if you have multiple default GW you need to check the one with lowest metric – maxadamo Mar 23 '20 at 22:35

How to get my machine's IP address from Ruby without leveraging from other IP address?

5 Answers5

Linked