$ find /sys/ -type f -name carrier
/sys/devices/virtual/net/lo/carrier
/sys/devices/pci0000:00/0000:00:19.0/net/eth0/carrier
/sys/devices/pci0000:00/0000:00:1c.4/0000:02:00.0/net/eth2/carrier
/sys/devices/pci0000:00/0000:00:1c.4/0000:02:00.1/net/eth3/carrier
/sys/devices/pci0000:00/0000:00:1c.4/0000:02:00.2/net/eth4/carrier
/sys/devices/pci0000:00/0000:00:1c.4/0000:02:00.3/net/eth5/carrier
/sys/devices/pci0000:00/0000:00:1c.6/0000:03:00.0/net/eth1/carrier