source: drbl-virt/sbin/duplicate_del_MAC @ 185

#!/bin/bash
# Program:
#   Delete duplicating ip & hostname
# Author: 
#   Rock {waue, shunfa, rock}@nchc.org.tw
# Version:
#    1.0
# History:
#   2010/08/26  Rock    First release (1.0)

# 刪掉空白行
#sed -i '/^$/d' "$1"

#read -p "cp - f $1 ${1}.old ; $?"
cp $1 $1.$(date +%Y-%m-%d-%H-%M-%S).drbl-virt_bak 

# Delete duplating VM IP
for vm_ip in $(echo $VM_IPs)
do
    vm_ip_lines=$(cat -n $1 | grep $vm_ip | awk '{print $1}' )
    # no duplicated vlaue, doesn't do it
    if [ -n $vm_ip_lines ]; then
        vm_ip_count=$(echo $vm_ip_lines | wc -w)

        for (( i=1; i<=${VM_ip_count}; i++ ))
        do
            del_line=$(echo $vm_ip_lines | cut -d " " -f${i})
            sed -i "${del_line}d" $1
        done
    fi
done
  
# Dlete duplicating hostname in file
for vm_host in $(echo $VM_hosts)
do
    # line numbers
    vm_host_lines=$(cat -n $1 | grep "$vm_host" | awk '{print $1}')
    # no duplicated vlaue, doesn't do it
    if [ -n $vm_host_lines ]; then
        vm_host_count=$(echo $vm_host_lines | wc -w)
  
        for (( i=1; i<=${vm_host_count}; i++ ))
        do
            del_line=$(echo $vm_host_lines | cut -d " " -f${i})
            sed -i "${del_line}d" $1
        done                                                                                                                                                             
    fi
done