IO_GETEVENTS(2)           (2020-12-21)            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
          Note: this page describes the raw Linux system call inter-
          face.  The wrapper function provided by libaio uses a dif-
          ferent 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
          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.

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     IO_GETEVENTS(2)           (2020-12-21)            IO_GETEVENTS(2)

          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 conven-
          tions 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 indicat-
          ing 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 5.10 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/.

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