方法一：nmcli
输出中参数WIRED-PROPERTIES.CARRIER为on即为接网线网卡
#nmcli device show |grep -i -E "device|carrier"
GENERAL.DEVICE:                         ens224
WIRED-PROPERTIES.CARRIER:               on
如下命令将输出内容合并为一行，只看{BANNED}{BANNED}{BANNED}{BANNED}{BANNED}最佳佳佳佳佳后一列为on即可
#nmcli device show |awk '/DEVICE/{t=$0}/CARRIER/{print t,$0}'
GENERAL.DEVICE: ens224    **WIRED-PROPERTIES.CARRIER: on
**
方法二：ifconfig
输出中状态为RUNNING的接口卡即为接网线网卡
# ifconfig |grep RUNNING
ens224: flags=4163RUNNING,MULTICAST>  mtu 1500

方法三：ethtool来检查，主要关注的字段为"Link detected"，注意如下的输出是插上网线的：
# ethtool ens224
Settings for ens224:
        Supported ports: [ TP ]
        Supported link modes:   1000baseT/Full
                                10000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: No
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: 10000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: off
        MDI-X: Unknown
        Supports Wake-on: uag
        Wake-on: d
       Link detected: yes