/proc/net/dev

cat /proc/net/dev
Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
   lo: 5464093551 3826029    0    0    0     0          0         0 5464093551 3826029    0    0    0     0       0          0
 eth0: 1191959595 5678723    0    0    0     0          0         0 5234245511 5103603    0    0    0     0       0          0

See also

• /proc/
• ifconfig, ip, /proc/net/dev, ifconfig -a