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Re: what's the right way to resolve localhost's IPs

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On 2023-03-22 10:06, Jeremy Ardley wrote:
> On 22/3/23 09:12, fh@dnsbed.com wrote:
>> Hello,
>> 
>> In my shell script, how to get the localhost's IPs (eth0 and eth1) 
>> correctly?
>> I know I can run 'ifconfig' and grep etc, but it's maybe not that 
>> graceful.
> 
> On Debian the preferred  command is
> 
> root@debian12:~# ip a
> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
> group default qlen 1000
>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>     inet 127.0.0.1/8 scope host lo
>        valid_lft forever preferred_lft forever
>     inet6 ::1/128 scope host
>        valid_lft forever preferred_lft forever
> 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel 
> state UP group default qlen 1000
>     link/ether 08:00:27:18:b6:ac brd ff:ff:ff:ff:ff:ff
>     inet 10.31.40.166/24 brd 10.31.40.255 scope global dynamic enp0s3
>        valid_lft 81816sec preferred_lft 81816sec
>     inet6 2403:5800:c101:b700:a00:27ff:fe18:b6ac/64 scope global 
> dynamic mngtmpaddr
>        valid_lft 6667sec preferred_lft 3066sec
>     inet6 fe80::a00:27ff:fe18:b6ac/64 scope link
>        valid_lft forever preferred_lft forever
> 
> You can also output in .json format
> 
> root@debian12:~# ip -j a
>
[{"ifindex":1,"ifname":"lo","flags":["LOOPBACK","UP","LOWER_UP"],"mtu":65536,"qdisc":"noqueue","operstate":"UNKNOWN","group":"default","txqlen":1000,"link_type":"loopback","address":"00:00:00:00:00:00","broadcast":"00:00:00:00:00:00","addr_info":[{"family":"inet","local":"127.0.0.1","prefixlen":8,"scope":"host","label":"lo","valid_life_time":4294967295,"preferred_life_time":4294967295},{"family":"inet6","local":"::1","prefixlen":128,"scope":"host","valid_life_time":4294967295,"preferred_life_time":4294967295}]},{"ifindex":2,"ifname":"enp0s3","flags":["BROADCAST","MULTICAST","UP","LOWER_UP"],"mtu":1500,"qdisc":"fq_codel","operstate":"UP","group":"default","txqlen":1000,"link_type":"ether","address":"08:00:27:18:b6:ac","broadcast":"ff:ff:ff:ff:ff:ff","addr_info":[{"family":"inet","local":"10.31.40.166","prefixlen":24,"broadcast":"10.31.40.255","scope":"global","dynamic":true,"label":"enp0s3","valid_life_time":81787,"preferred_life_time":81787},{"family":"inet6","local":"2403:5800:c101:
b700:a00:27ff:fe18:b6ac","prefixlen":64,"scope":"global","dynamic":true,"mngtmpaddr":true,"valid_life_time":6638,"preferred_life_time":3037},{"family":"inet6","local":"fe80::a00:27ff:fe18:b6ac","prefixlen":64,"scope":"link","valid_life_time":4294967295,"preferred_life_time":4294967295}]}]
> 
> and if you write a script like this (and make it write protected and 
> executable)
> 
>  cat ipv4_addresses.py
> #!/usr/bin/env python3
> import json
> import sys
> 
> data = sys.stdin.read()
> 
> interfaces = json.loads(data)
> 
> for interface in interfaces:
>     ifname = interface['ifname']
>     for addr_info in interface['addr_info']:
>         if addr_info['family'] == 'inet':
>             ipv4 = addr_info['local']
>             print(f"{ifname}: {ipv4}")
> 
> you can do
> 
> ip -j a | ./ipv4_addresses.py
> lo: 127.0.0.1
> enp7s0: 10.31.40.68
> 
> or on a fancier setup
> 

Thanks a lot. Now I prefer this way:
$ ip -j a|python3 -mjson.tool

regards.

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what's the right way to resolve localhost's IPs fh@dnsbed.com - 2023-03-22 02:20 +0100
  Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-22 03:10 +0100
    Re: what's the right way to resolve localhost's IPs fh@dnsbed.com - 2023-03-22 03:40 +0100
    Re: what's the right way to resolve localhost's IPs Gregory Seidman <gsslist+debian@anthropohedron.net> - 2023-03-22 21:40 +0100
    Re: what's the right way to resolve localhost's IPs Tom Furie <tom@furie.org.uk> - 2023-03-22 22:20 +0100
      Re: what's the right way to resolve localhost's IPs Greg Wooledge <greg@wooledge.org> - 2023-03-22 22:50 +0100
        Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-23 00:10 +0100
          Re: what's the right way to resolve localhost's IPs Greg Wooledge <greg@wooledge.org> - 2023-03-23 00:40 +0100
            Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-23 01:00 +0100
              Re: what's the right way to resolve localhost's IPs Nicolas George <george@nsup.org> - 2023-03-23 08:50 +0100
                Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-23 09:00 +0100
                Re: what's the right way to resolve localhost's IPs Lee <ler762@gmail.com> - 2023-03-23 12:00 +0100
  Re: what's the right way to resolve localhost's IPs Emanuel Berg <incal@dataswamp.org> - 2023-03-30 07:50 +0200
    Re: what's the right way to resolve localhost's IPs fh@dnsbed.com - 2023-03-30 10:10 +0200

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