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CentOS 7.0 - man page for io_getevents (centos section 2)

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, where a NULL timeout waits until at least min_nr events have been seen. Note that timeout is relative.
RETURN VALUE
On success, io_getevents() returns the number of events read: 0 if no events are available, or less than min_nr if the timeout has elapsed. For the failure return, see NOTES.
ERRORS
EFAULT Either events or timeout is an invalid pointer. EINVAL ctx_id is invalid. min_nr is out of range or nr is out of range. EINTR Interrupted by a signal handler; see signal(7). 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 genenerating 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 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2013-04-08 IO_GETEVENTS(2)
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