io_getevents(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON

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>    /* Definition of *io_* types */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_io_getevents, aio_context_t ctx_id,
                   long min_nr, long nr, struct io_event *events,
                   struct timespec *timeout);

       Note: glibc provides no wrapper for io_getevents(), necessitating
       the use of syscall(2).

DESCRIPTION         top

       Note: this page describes the raw Linux system call interface.
       The wrapper function provided by libaio uses a different type for
       the ctx_id argument.  See NOTES.

       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
              range.

       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

       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),
       time(7)

COLOPHON         top

       This page is part of release 5.12 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
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22                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)