io_getevents(2) — Linux manual page


IO_GETEVENTS(2)           Linux Programmer's Manual          IO_GETEVENTS(2)

NAME         top

       io_getevents - read asynchronous I/O events from the completion queue

SYNOPSIS         top

       #include <linux/aio_abi.h>         /* Defines needed types */
       #include <linux/time.h>            /* Defines 'struct timespec' */

       int io_getevents(io_context_t ctx_id, long min_nr, long nr,
                        struct io_event *events, struct timespec *timeout);

       Note: There is no glibc wrapper for this system call; see NOTES.

DESCRIPTION         top

       The io_getevents() system call attempts to read at least min_nr
       events and up to nr events from the completion queue of the AIO
       context specified by ctx_id.

       The timeout argument specifies the amount of time to wait for events,
       and is specified as a relative timeout in a structure of the
       following form:

           struct timespec {
               time_t tv_sec;      /* seconds */
               long   tv_nsec;     /* nanoseconds [0 .. 999999999] */

       The specified time will be rounded up to the system clock granularity
       and is guaranteed not to expire early.

       Specifying timeout as NULL means block indefinitely until at least
       min_nr events have been obtained.

RETURN VALUE         top

       On success, io_getevents() returns the number of events read.  This
       may be 0, or a value less than min_nr, if the timeout expired.  It
       may also be a nonzero value less than min_nr, if the call was
       interrupted by a signal handler.

       For the failure return, see NOTES.

ERRORS         top

       EFAULT Either events or timeout is an invalid pointer.

       EINTR  Interrupted by a signal handler; see signal(7).

       EINVAL ctx_id is invalid.  min_nr is out of range or nr is out of

       ENOSYS io_getevents() is not implemented on this architecture.

VERSIONS         top

       The asynchronous I/O system calls first appeared in Linux 2.5.

CONFORMING TO         top

       io_getevents() is Linux-specific and should not be used in programs
       that are intended to be portable.

NOTES         top

       Glibc does not provide a wrapper function for this system call.  You
       could invoke it using syscall(2).  But instead, you probably want to
       use the io_getevents() wrapper function provided by libaio.

       Note that the libaio wrapper function uses a different type
       (io_context_t) for the ctx_id argument.  Note also that the libaio
       wrapper does not follow the usual C library conventions for
       indicating errors: on error it returns a negated error number (the
       negative of one of the values listed in ERRORS).  If the system call
       is invoked via syscall(2), then the return value follows the usual
       conventions for indicating an error: -1, with errno set to a
       (positive) value that indicates the error.

BUGS         top

       An invalid ctx_id may cause a segmentation fault instead of
       generating the error EINVAL.

SEE ALSO         top

       io_cancel(2), io_destroy(2), io_setup(2), io_submit(2), aio(7),

COLOPHON         top

       This page is part of release 5.09 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                            2020-06-09                  IO_GETEVENTS(2)

Pages that refer to this page: io_cancel(2)io_destroy(2)io_setup(2)io_submit(2)syscalls(2)aio(7)signal(7)