Query send buffer usage on a socket in linux

Question

Is it possible to query how many bytes are in a socket's send buffer in linux? I'd like to be able to query SO_SNDBUF with getsockopt to get the buffer size and then [insert technique here] to get the actual usage, which will let me know how much I'm filling up the buffer.

Answer 1

That's not what SO_SNDBUF does. SO_SNDBUF sets or gets the maximum socket send buffer in bytes (quoting socket(7) ). You could probably use the SIOCOUTQ or TIOCOUTQ ioctls if you're using tcp or udp .

However, it's highly unlikely this is the right approach . Have you considered using a select-like mechanism to notify you when a socket is writable ? Combined with nonblocking behavior it could be the ticket to a clean approach.