Network Connectivity

[Vu Pham]

On 08/10/2012 02:14 AM, Steve Jardine wrote:
> All,
>
>     Does anyone have an idea as to how to determine if any device has network connectivity. Where devices are WiFi (wlan0), Ethernet (Eth0), Wireless (usb0-2)? I need to trigger an event if network connectivity exists.
>
>     Steve
>

Two places I will look at :
1. /sys/class/net

- Each network device has a separate directory.
[vu at vpepper ~]$ ls /sys/class/net
eth0  eth1  lo  sit0

- Each of these directories has files that contain information about 
that device, including the network connectivity.
[vu at vpepper ~]$ ls /sys/class/net/eth0
address    device    ifindex    operstate  statistics    uevent
addr_len   dormant   iflink     rxbuf_cur  subsystem     weight
broadcast  features  link_mode  rxbuf_max  tx_queue_len
carrier    flags     mtu        rxbuf_min  type

- the file operstate shows that current status of the device.
[vu at vpepper ~]$ cat /sys/class/net/eth0/operstate
up

Other files such as carrier, iflink ... may help, too.



2. udev: the udev scripts can change your device names, or to make it 
consistent.
If you want the LAN devices always ethX , no matter what drivers they 
use, then udev scripts can help.

Vu