CODEWITHSUNDEEP
linuxcommand-linesed
silvamerica
silvamerica

Reputation: 994

Replace ip address with hostname using sed or other command-line tool

I have a command that outputs something like this:

192.168.1.1        182
192.168.1.10       300
192.168.4.50       64

I want to pipe this through sed or some other linux command-line tool and replace the IP addresses with their hostname from the 'host ' command, like this:

web.hostname.com     182
db.hostname.com      300
search.hostname.com  64

How would I go about doing this?

Upvotes: 1

Views: 2331

Answers (2)

Chris Stratton
Chris Stratton

Reputation: 40407

I can't figure out how to get sed to use the evaluation of a command (in backticks) in the replace string and pass it one of the matched subexpressions as an argument, but maybe someone else can.

If you are in bash, you could pipe it into this:

while read ip whatever ; do hostname=`host $ip | grep pointer` ; \
if [ -n "$hostname" ] ; then echo `host $ip` $whatever | \
sed 's/\(^.* pointer \)\(.*\)\./\2/g'  ; else echo $ip $whatever ; fi ; done

(This tries to pull the hostname out of the response, and leave the ip address numeric if the result of the lookup isn't a hostname)

Upvotes: 0

soulmerge
soulmerge

Reputation: 75774

Looks a bit tricky, but should do what you need:

your_command | while read HOST NUM; do host $HOST | tr "\n" " "; echo $NUM; done

Upvotes: 1

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