[Cialug] Just Tell Me The IP!

[Scott Yates]

Darnit, that won't work either, sorry.  Interesting problem though.

On Thu, May 21, 2020 at 12:13 PM Scott Yates <Scott at yatesframe.com> wrote:

> You might try the output of "route".  I think it is more universal, and
> might be easier to parse out.
>
> On Thu, May 21, 2020 at 12:11 PM Todd Walton <tdwalton at gmail.com> wrote:
>
>> I'm running a mix of CentOS, Amazon Linux, and Ubuntu. The CentOS servers
>> span three generations, the Amazon Linux, like, four. And you know what's
>> surprisingly complicated to do across a variety of distributions and
>> versions? Tell me the IP of the server I'm on. Well, if I'm "on" the
>> server, it's just a couple of quick commands and an eyeball. But I need a
>> way to do it by script.
>>
>> Problems include:
>>
>> * The "ip" command shows up in three different locations, depending on
>> distribution.
>> * The "ifconfig" command shows up in 2 different locations.
>> * You can run those just fine sans sudo, but sbin is typically not in a
>> user's PATH.
>> * Network device names vary across distributions.
>> * Some servers have multiple IPs. I need one, it needs to be from a
>> "physical" device, and it needs to be the same one every time.
>> * ip's output varies across versions
>> * ip has json output, but only for a couple years now, so it's not in any
>> of my distros </grouse>
>>
>> Is there just no reliable way to get a server's "primary" IP that works
>> across distros and distro versions? I wish there was something like
>> "hostname" that just spat back /the IP address/.
>>
>> This is what I'm doing right now:
>>
>> HOSTIP=$(find /sys/devices -type d -name 'net' -not -path '*/virtual/*'
>> -print | xargs -I% find % -mindepth 1 -maxdepth 1 -exec basename {} + |
>> grep -P '^e' | xargs -n1 ifconfig | grep 'inet ' | tr -s ' ' | sed -e
>> 's/^[[:space:]]\+//g' -e 's/addr://g' | cut -d\  -f2 | sort | head -n1)
>> if [[ -z $HOSTIP ]]; then HOSTIP='$(ifconfig | grep 'inet ' | tr -s ' ' |
>> sed -e 's/^[[:space:]]\+//g' -e 's/addr://g' | cut -d\  -f2 | sort | head
>> -n1)'; fi
>> if [[ -z $HOSTIP ]]; then HOSTIP='127.0.0.1'; fi
>>
>> It's fraught with disappointment, but less than anything else I've tried
>> so
>> far.
>>
>> (Also, I didn't realize until this little adventure that xargs will always
>> run once, even without input, unless you explicitly tell it not to. Ugh.)
>>
>> --
>> Todd
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>