工具 ethtool
如果没有安装，则sudo apt-get install ethtool
终端运行 sudo ethtool eth0
结果1：（网线插入时）
p { margin-bottom: 0.08in; }
Supported
ports: [ TP MII ]
Supported
link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Supports
auto-negotiation: Yes
Advertised
link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Advertised
pause frame use: No
Advertised
auto-negotiation: Yes
Link
partner advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Link
partner advertised pause frame use: No
Link
partner advertised auto-negotiation: Yes
Speed:
100Mb/s
Duplex:
Full
Port:
MII
PHYAD:
0
Transceiver:
internal
Auto-negotiation:
on
Supports
Wake-on: pumbg
Wake-on:
g
Current
message level: 0x00000033 (51)
Link
detected: yes
结果2（网线拔除时）：
p { margin-bottom: 0.08in; }
Supported
ports: [ TP MII ]
Supported
link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Supports
auto-negotiation: Yes
Advertised
link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Advertised
pause frame use: No
Advertised
auto-negotiation: Yes
Link
partner advertised link modes: Not reported
Link
partner advertised pause frame use: No
Link
partner advertised auto-negotiation: No
Speed:
10Mb/s
Duplex:
Half
Port:
MII
PHYAD:
0
Transceiver:
internal
Auto-negotiation:
on
Supports
Wake-on: pumbg
Wake-on:
g
Current
message level: 0x00000033 (51)
Link
detected: no
可见可以根据grep"link detected: yes"的结果来判断是否插入网线
shell 中写下列代码
ethtool eth0 | grep "Link detected: yes"
判断一下上面这条命令的输出就可以知道网线是不是接上了
if 上面的输出为空， 那么网线就是没有接上的
else 网线连接正常。