Get network speed from system files on Linux

Question

At which files should I look to check the (current) download/upload speed? I remember doing so a long time ago. The files I read did not contain the speed directly, but I could calculate the speed with simple arithmetic.

EDIT: I found it, it's /proc/net/dev. It shows the sent and received bytes that I just sample every second.

Answer 1

I do not know of a file that can be read to obtain this information.

If you want the maximum connection speed supported by interface eth0 you can try this as root:

ethtool eth0

Or

mii-tool eth0

If you are looking to test your network speed instead, you might be interested in this StackOverflow question. If instead you hope to actively monitor usage of a network interface you could use a utility like slurm.