linux读取问文本文件第一行写入hosts

#!/bin/bash
file=/www/web/open35zhcom/public_html/iplist.txt
ip=`awk 'NR==1' $file |awk '{print $1}'`
cat /dev/null >>/etc/hosts
cat >>/etc/hosts<<eof
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
$ip         oa2.35zh.com
eof