Network Interface Status
 

The ifconfig command somehow knows which interfaces are up and which are down. I'm writing a daemon that needs to know if a particular interface is up or down. What functions are used to determine if an interface is up or down?

There is a special file in /proc/net called dev. Its contents show the active interfaces and some statistics for each iface. Reading and parsing that file sounds like the easiest route to me.

Gary

I've looked at this file, but it appears to contain any interface that's ever been up on the system.

There are several ioctls for getting the interfaces and its status. I would search for SIOCGIFCONF and ioctl. There's a structure that has a flag which you can query for IFF_UP. I can't remember it on top of my head, but that should be enough to point you to the right direction.

interface status
 

i have one doubt regarding using /proc/net/dev file.interface are up then cont of transmitted packets,transmitted bytes,received packets and recived bytes is incremented.if one interface is down that suddenly file shows some count value.how will i decide from count wheter interface is up or down.the structure that writes the data to the /proc/net/dev available in which file.is there any information regarding structure please respond.

i have some doubts regarding using /proc/net/dev file.interface are up then cont of transmitted packets,transmitted bytes,received packets and recived bytes is incremented.if one interface is down suddenly the file shows some count value.how will i decide from count wheter interface is up or down.