io_uring_peek_cqe(3)            liburing Manual           io_uring_peek_cqe(3)

NAME
       io_uring_peek_cqe - check if an io_uring completion event is available

SYNOPSIS
       #include <liburing.h>

       int io_uring_peek_cqe(struct io_uring *ring,
                             struct io_uring_cqe **cqe_ptr);

       int io_uring_peek_batch_cqe(struct io_uring *ring,
                                   struct io_uring_cqe **cqe_ptrs,
                                   unsigned count );"

DESCRIPTION
       The io_uring_peek_cqe(3) function returns an IO completion from the
       queue belonging to the ring param, if one is readily available. On
       successful return, cqe_ptr param is filled with a valid CQE entry.

       This function does not enter the kernel to wait for an event, an event
       is only returned if it's already available in the CQ ring.

       The io_uring_peek_batch_cqe(3) function returns up to count request
       completions in cqe_ptrs belonging to the ring param, if they are
       readily available. It will not enter the kernel, unless the CQ ring is
       in an overflow condition. Upon successful return, cqe_ptrs are filled
       with the number of events indicated by the return value.


RETURN VALUE
       On success io_uring_peek_cqe(3) returns 0 and the cqe_ptr parameter is
       filled in. On success io_uring_peek_batch_cqe(3) returns the number of
       completions filled in. On failure, they may return -EAGAIN.

SEE ALSO
       io_uring_submit(3), io_uring_wait_cqes(3), io_uring_wait_cqe(3)

liburing-2.2                    March 12, 2022            io_uring_peek_cqe(3)