IP地址脚本化

[sunflyer]

pppoe连接建立后，系统自动调用/etc/ppp/ip-up脚本。
其参数如下面文件所示，第4个参数是系统获得的动态ip。

Script which handles the routing issues as necessary for pppd
Only the link to Newman requires this handling.
When the ppp link comes up, this script is called with the following
parameters
$1 the interface name used by pppd (e.g. ppp3)
$2 the tty device name
$3 the tty device speed
$4 the local IP address for the interface
$5 the remote IP address
$6 the parameter specified by the 'ipparam' option to pppd

[sunflyer]

$4应该就可以获取到IP地址了，原则上应该不需要自己去做COMMAND