recvfd - receive a file descriptor from a local socket peer
#include <sys/socket.h>
int recvfd(int sockfd, int options);Receive an open file descriptor from a local socket peer connected via sockfd. This is a non-blocking call that will fail if there is no file descriptor waiting in the socket's queue.
File descriptors are sent out-of-band and do not affect the regular data streams.
The options argument accepts a bitmask of the following flags:
O_CLOEXEC: The opened fd shall be closed on exec(2).If a file descriptor is successfully received, it is returned as a non-negative integer. Otherwise, -1 is returned and errno is set to indicate the error.
EBADF: sockfd is not an open file descriptor.ENOTSOCK: sockfd does not refer to a socket.EAFNOSUPPORT: sockfd does not refer to a local domain socket.EINVAL: sockfd does not refer to a connected or accepted socket.EAGAIN: There is no file descriptor queued on this socket.recvfd() was first introduced in Plan 9 from User Space.