LinuxQuestions.org - A script to thoroughly resolve a hostname into IP addresses

Since sometimes `dig example.com +short` returns more hostnames, here's a script to thoroughly resolve all the results into only IP addresses.

Code:

#!/bin/bash

/**

 * paramater 1: a string

 * return: 0 hostname

 * return: 1 ip address

 */

function is_ip_address()

{

        R=`echo $1 | egrep "[a-z]"`

        r=$?

        if [ -z "$R" ]

        then

                return 1

        fi

        return 0



}



#

# parameter 1: a hostname to resolve

# side effects: echos IP addresses (which may not be unique)

function resolve_hostname()

{

        is_ip_address $1

        if [[ $? -eq 1 ]]

        then

                echo "$1"

                return

        fi

        for a in `dig $1 +short`

        do

                resolve_hostname $a

        done

}





# general way to call the function

resolve_hostname "www.concentric.net"

# you can also assign the output to a variable

# and make the results unique

r=`resolve_hostname "real.npr.org" | sort |uniq`

echo $r