io_getevents
Section: System Calls (2)
Updated: 202-0-21
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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
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
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_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.
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)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- STANDARDS
-
- HISTORY
-
- BUGS
-
- SEE ALSO
-
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