Another option is to use the /proc filesystem. The /proc/net/dev file contains statistics about the configured network interfaces. Each line is dedicated to one network interface and it contains statistics for receive and transmit. The statistics include metrics such total number of received/transmittted bytes, packets, drops, errors and so on.
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: 29846937 129576 0 0 0 0 0 0 29846937 129576 0 0 0 0 0 0
wlan0: 9467393340 8027251 0 0 0 0 0 0 2559312961 5896509 0 0 0 0 0 0
Or you can try the netstat command which can display all network interfaces and related statistics:
netstat -i
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
lo 65536 0 130435 0 0 0 130435 0 0 0 LRU
wlan0 1492 0 8028018 0 0 0 5897361 0 0 0 BMRU