NAME

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

SYNOPSIS

       #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

       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

       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

       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 5.13 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/.