asked on

Parse output of Host command and place into a variable

Hi,

Is there a more efficient way to capture the 1st IP address from the output of the HOST command.

Currently I have the following:

host bbc.co.uk | awk '{match($0,/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/); ip = substr($0,RSTART,RLENGTH); print ip}'|awk '/./' |awk 'NR==1{print $1}'

Open in new window

Thx
Nev

woolmilkporc

Why not just

VAR=$(host bbc.co.uk | awk 'NR==1 {print $4}')
echo $VAR

or

VAR=$(host bbc.co.uk | awk 'NR==1 {print $NF}')
echo $VAR

?

What is the unfiltered output of your host command?
On many UNIXes you must use $3 instead of $4.
$NF should work anyway, however.

collinsn

ASKER

Hi,

Here is a couple of example output of HOST. I'm just interested in capturing the first IPV4 IP address. It can be any HOST.

# host google.co.uk
google.co.uk has address 216.58.208.35
google.co.uk has IPv6 address 2a00:1450:4009:80d::2003
google.co.uk mail is handled by 10 aspmx.l.google.com.
google.co.uk mail is handled by 50 alt4.aspmx.l.google.com.
google.co.uk mail is handled by 30 alt2.aspmx.l.google.com.
google.co.uk mail is handled by 20 alt1.aspmx.l.google.com.
google.co.uk mail is handled by 40 alt3.aspmx.l.google.com.

# host ps4updptl.uk.np.community.playstation.net
ps4updptl.uk.np.community.playstation.net is an alias for elb001-p4ci01.p4ci.usw2.np.cy.s0.playstation.net.
elb001-p4ci01.p4ci.usw2.np.cy.s0.playstation.net is an alias for p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com.
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 54.213.83.95
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 52.11.91.131
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 54.218.107.56
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 52.11.92.13
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 54.191.178.65
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 54.201.171.253
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 52.11.88.38
p4ci-np-s-loadbala-sv3h6h0sxu8-369221137.us-west-2.elb.amazonaws.com has address 52.11.90.17

woolmilkporc

Try this:

VAR=$(host bbc.co.uk | awk '/has address/ {print $NF; exit}')
echo $VAR

Gerwin Jansen

VAR=$(host bbc.co.uk | head -1 | cut -d" " -f4)

A bit shorter and in case you don't want to use awk :)

woolmilkporc

@Gerwin,

your command will sometimes return "alias" or "address" or so, depending on the (varying!) output sequence of the "host" command (see the example for host "ps4updptl.uk.np.community.playstation.net" posted by collinsn).

They're after the first IPv4 address instead (54.213.83.95 in the example) - if I understood everything right, that is.

The fact that the output can vary in sequence makes the attribute "first" a bit questionable, however.

Gerwin Jansen

You're right, adding grep -v alias would fix that but that's almost the same as grepping for "has address" :)

collinsn

ASKER

Sorry, I've been off sick for a while a completely forgot about this post. Both suggestion were accepted, but what I really needed was for it to validate the address as a valid ip4 address.

woolmilkporc

Hi,

I hope you're well again!

I'm rather sure that "host" will never display an invalid IP, but you can check it anyway like this:

VAR=$(host bbc.co.uk | awk '/has address/ {print $NF; exit}')
if egrep -q '^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$' <<<$VAR; then
myIFS=$IFS; IFS='.'
A=($VAR); IFS=$myIFS
if [[ ${A[0]} -lt 256 && ${A[1]} -lt 256 && ${A[2]} -lt 256 && ${A[3]} -lt 256 ]]; then
VALID=true
fi
fi
[[ $VALID = "true" ]] && echo $VAR is valid || echo $VAR is invalid

ASKER CERTIFIED SOLUTION

woolmilkporc

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial