io_getevents(2) System Calls Manual io_getevents(2)
NAME
io_getevents - read asynchronous I/O events from the completion queue
LIBRARY
Standard C library (libc, -lc)
Alternatively, Asynchronous I/O library (libaio, -laio); see VERSIONS.
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 VERSIONS.
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 speci-
fied by ctx_id.
The timeout argument specifies the amount of time to wait for events,
and is specified as a relative timeout in a timespec(3) structure.
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 VERSIONS.
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
You probably want to use the io_getevents() wrapper function provided
by libaio.
Note that the libaio wrapper function uses a different type (io_con-
text_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 in-
dicating an error: -1, with errno set to a (positive) value that indi-
cates the error.
STANDARDS
Linux.
HISTORY
Linux 2.5.
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), timespec(3),
aio(7), time(7)
Linux man-pages 6.7 2023-10-31 io_getevents(2)
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