io_getevents

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



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

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

       int io_getevents(aio_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
       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
       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
       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
       The asynchronous I/O system calls first appeared in Linux 2.5.

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

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

SEE ALSO
       io_cancel(2), io_destroy(2), io_setup(2), io_submit(2), aio(7), time(7)

COLOPHON
       This page is part of release 5.04 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                             2017-09-15                   IO_GETEVENTS(2)