How to get network interface speed programactically on Linux?

Question

I am wondering about the speed as show in the network connection information, e.g. 100Mb/s, 10Mb/s, not the available bandwidth. Thanks in advance!

Answer 1

found on http://linuxhelp.blogspot.com/2005/10/find-speed-of-your-ethernet-card-in.html

programatically read this info and parse it, looking for 100baseTx or similar

# mii-tool -v eth0
eth0: negotiated 100baseTx-FD flow-control, link ok
  product info: vendor 00:00:20, model 32 rev 1
  basic mode:   autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising:  100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
  link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control

also, on same article you could use this and look for the "speed:" line

#ethtool eth0

Settings for eth0:
  Supported ports: [ TP MII ]
  Supported link modes:   10baseT/Half 10baseT/Full
                          100baseT/Half 100baseT/Full
  Supports auto-negotiation: Yes
  Advertised link modes:  10baseT/Half 10baseT/Full
                          100baseT/Half 100baseT/Full
  Advertised auto-negotiation: Yes
  Speed: 100Mb/s
  Duplex: Full
  Port: MII
  PHYAD: 32
  Transceiver: internal
  Auto-negotiation: on
  Supports Wake-on: pumbg
  Wake-on: p
  Current message level: 0x00000007 (7)
  Link detected: yes

Answer 2

If you want to do that in C code, look up mii-tool.c