CODEWITHSUNDEEP
regexbashawksedgrep
Amy
Amy

Reputation: 1

How can I grab next Word after Regex in bash?

I am trying to grab the Word from a text file AFTER the IP regex match ($2):

fileName.txt:

IP hostname blah blah blah...

blah blah..

IP hostname blah blah blah... . . .

I want the hostnames for each instance of the IP (which I found with grep regex and stored it in $var). I want to use found hostnames to set to $host and print them out onto a text file with the IPs (which are already done).

I have tried multiple methods from online answers but they all printed blanks.

Thank you!

Upvotes: 0

Views: 123

Answers (2)

karakfa
karakfa

Reputation: 67467

awk to the rescue!

$ awk  '/^([0-9]{1,3}\.){3}[0-9]{1,3}/{print $1, $2}'

will give you IP hostname for the lines starting with the matching regex.

if your awk doesn't support regex interval you need the add --re-interval option.

Upvotes: 0

Charles Duffy
Charles Duffy

Reputation: 295278

See BashFAQ #1 for guidance on how best to read from a stream.

#!/bin/bash
#      ^^^^ important, not /bin/sh

while read -r -a words; do
    # put the array words into $1, $2, $3, etc.
    set -- "${words[@]}"

    # put $1 -- the first word -- into the variable named "ip"
    ip=$1

    # remove $1, leaving only hostnames in $1, $2, etc
    shift

    echo "IP address $ip has the following hostnames:"
    for hostname; do # by default, a for loop iterates over $@
      echo "- ${hostname}"
    done
done < <(grep '[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}' test_amy_hostrun.txt)

Upvotes: 1

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