CODEWITHSUNDEEP
bash
user3183570
user3183570

Reputation: 3

How to compare two columns of IP and hostnames grepped from multiple files in bash

I'm attempting to grep IPs from a number of files, look them up in DNS and compare them to the hostnames already in the same files to ensure both are correct. Then print out anything that is wrong.

I've gathered I need to put the information into arrays and diff them somehow.

Here is my horrible bash code which does not work. I'm pretty sure at least my for loop is wrong:

declare -a ipaddr=(`grep -h address *test.com.cfg | awk '{print $2}'`)
declare -a host_names=(`grep -h address *test.com.cfg | awk '{print $2}'`)

for i in "${ipaddr[@]}"
do
lookedup_host_names=( $(/usr/sbin/host ${ipaddr[@]} | awk '{print $5}' | cut -d. -f1-4 | tr '[:upper:]' '[:lower:]'))
done
if [[ -z diff <(printf "%s\n" "${lookedup_host_names[@]}"| sort ) <(printf "%s\n" "${host_names[@]}"| sort) ]]
then
printf "%s\n" "${lookedup_host_names[@]}"
fi

Upvotes: 0

Views: 166

Answers (2)

that other guy
that other guy

Reputation: 123600

The two principal problems are that your for loop overwrites the array each time rather than appending, and your diff check is invalid.

To quickly fix the for loop, you could use += instead of =, .e.g lookedup_host_names+=( ... ).

To do the diff, you don't really need a condition. You could just run 

diff <(printf "%s\n" "${host_names[@]}"| sort ) <(printf "%s\n" "${lookedup_host_names[@]}"| sort)

and it would show any differences between the two in diff format which most Unix users are familiar with (note that I switched the arguments around, since the first argument is supposed to be original).

If, like in your example, you actually do want to compare them and show the entire final list if there is a difference, you could do 

if diff <(printf "%s\n" "${host_names[@]}"| sort ) <(printf "%s\n" "${lookedup_host_names[@]}"| sort) > /dev/null
then
    printf "%s\n" "${lookedup_host_names[@]}"
fi

Upvotes: 0

leu
leu

Reputation: 2081

I don't see a difference between your arrays ipaddr and host_names. Supposed your files contain lines like

address 1.2.3.4 somehost.tld

a script like this may do what you want.

cat *test.com.cfg | grep address | while read line; do  
    IP=$(awk {'print $2'}); 
    CO=$(awk {'print $3'}); 
    CN=$(host $CO | cut -d ' ' -f 4)
    [ "$CN" = "$IP" ] || echo "Error with IP $IP"; 
done

Upvotes: 1

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