Замена внешнего ip в конфиге Asterisk

Повесить скрипт в cron

#!/bin/bash
#
#This script change IP address in line 'externip=' in 
#/etc/asterisk/sip.conf file to current WAN IP address
#
wan_ip=$(dig +short myip.opendns.com @resolver1.opendns.com)
cfg="/etc/asterisk/sip.conf"
current_ip=$(grep '^externip=' $cfg | sed 's/externip=//g')
if
    [ "$wan_ip" != "$current_ip" ];
then
    tmp_cfg=$cfg".tmp"
    echo '[general]' > $tmp_cfg
    echo "externip=$wan_ip" >> $tmp_cfg
    cat $cfg | sed 1d | sed '/externip=/d' >>$tmp_cfg
    mv -f $tmp_cfg $cfg
    asterisk -rx "core reload"
else
    echo "WAN IP is equal IP in config file"
fi