How to get errno when epoll_wait returns EPOLLERR?

Question

Is there a way to find out the errno when epoll_wait returns EPOLLERR for a particular fd?

Is there any further information about the nature of the error?

Edit:

Adding more information to prevent ambiguity

epoll_wait waits on a number of file descriptors. When you call epoll_wait you pass it an array of epoll_event structures:

struct epoll_event {
           uint32_t     events;    /* Epoll events */
           epoll_data_t data;      /* User data variable */
       };

The epoll_data_t structure has the same details as the one you used with epoll_ctl to add a file descriptor to epoll:

typedef union epoll_data {
           void    *ptr;
           int      fd;
           uint32_t u32;
           uint64_t u64;
       } epoll_data_t;

What I'm looking for is what happens when there is an error on one of the file descriptors that epoll is waiting on.

ie: (epoll_event.events & EPOLLERR) == 1 - is there a way to find out more details of the error on the file descriptor?

Answer 1

Use getsockopt and SO_ERROR to get the pending error on the socket

int       error = 0;
socklen_t errlen = sizeof(error);
if (getsockopt(fd, SOL_SOCKET, SO_ERROR, (void *)&error, &errlen) == 0)
{
    printf("error = %s\n", strerror(error));
}