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io_getevents.html
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<!-- Creator : groff version 1.22.4 -->
<!-- CreationDate: Wed Jan 29 11:27:18 2020 -->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta name="generator" content="groff -Thtml, see www.gnu.org">
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<meta name="Content-Style" content="text/css">
<style type="text/css">
p { margin-top: 0; margin-bottom: 0; vertical-align: top }
pre { margin-top: 0; margin-bottom: 0; vertical-align: top }
table { margin-top: 0; margin-bottom: 0; vertical-align: top }
h1 { text-align: center }
</style>
<title>IO_GETEVENTS</title>
</head>
<body>
<h1 align="center">IO_GETEVENTS</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#RETURN VALUE">RETURN VALUE</a><br>
<a href="#ERRORS">ERRORS</a><br>
<a href="#VERSIONS">VERSIONS</a><br>
<a href="#CONFORMING TO">CONFORMING TO</a><br>
<a href="#NOTES">NOTES</a><br>
<a href="#BUGS">BUGS</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<a href="#COLOPHON">COLOPHON</a><br>
<hr>
<h2>NAME
<a name="NAME"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">io_getevents -
read asynchronous I/O events from the completion queue</p>
<h2>SYNOPSIS
<a name="SYNOPSIS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>#include
<linux/aio_abi.h></b> /* Defines needed types */
<b><br>
#include <linux/time.h></b> /* Defines ’struct
timespec’ */</p>
<p style="margin-left:11%; margin-top: 1em"><b>int
io_getevents(aio_context_t</b> <i>ctx_id</i><b>, long</b>
<i>min_nr</i><b>, long</b> <i>nr</i><b>, <br>
struct io_event *</b><i>events</i><b>, struct timespec
*</b><i>timeout</i><b>);</b></p>
<p style="margin-left:11%; margin-top: 1em"><i>Note</i>:
There is no glibc wrapper for this system call; see
NOTES.</p>
<h2>DESCRIPTION
<a name="DESCRIPTION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The
<b>io_getevents</b>() system call attempts to read at least
<i>min_nr</i> events and up to <i>nr</i> events from the
completion queue of the AIO context specified by
<i>ctx_id</i>.</p>
<p style="margin-left:11%; margin-top: 1em">The
<i>timeout</i> argument specifies the amount of time to wait
for events, and is specified as a relative timeout in a
structure of the following form:</p>
<p style="margin-left:17%; margin-top: 1em">struct timespec
{ <br>
time_t tv_sec; /* seconds */ <br>
long tv_nsec; /* nanoseconds [0 .. 999999999] */ <br>
};</p>
<p style="margin-left:11%; margin-top: 1em">The specified
time will be rounded up to the system clock granularity and
is guaranteed not to expire early.</p>
<p style="margin-left:11%; margin-top: 1em">Specifying
<i>timeout</i> as NULL means block indefinitely until at
least <i>min_nr</i> events have been obtained.</p>
<h2>RETURN VALUE
<a name="RETURN VALUE"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">On success,
<b>io_getevents</b>() returns the number of events read.
This may be 0, or a value less than <i>min_nr</i>, if the
<i>timeout</i> expired. It may also be a nonzero value less
than <i>min_nr</i>, if the call was interrupted by a signal
handler.</p>
<p style="margin-left:11%; margin-top: 1em">For the failure
return, see NOTES.</p>
<h2>ERRORS
<a name="ERRORS"></a>
</h2>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p style="margin-top: 1em"><b>EFAULT</b></p></td>
<td width="2%"></td>
<td width="78%">
<p style="margin-top: 1em">Either <i>events</i> or
<i>timeout</i> is an invalid pointer.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>EINTR</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Interrupted by a signal handler; see
<b>signal</b>(7).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>EINVAL</b></p></td>
<td width="2%"></td>
<td width="78%">
<p><i>ctx_id</i> is invalid. <i>min_nr</i> is out of range
or <i>nr</i> is out of range.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>ENOSYS</b></p></td>
<td width="2%"></td>
<td width="78%">
<p><b>io_getevents</b>() is not implemented on this
architecture.</p> </td></tr>
</table>
<h2>VERSIONS
<a name="VERSIONS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The
asynchronous I/O system calls first appeared in Linux
2.5.</p>
<h2>CONFORMING TO
<a name="CONFORMING TO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>io_getevents</b>()
is Linux-specific and should not be used in programs that
are intended to be portable.</p>
<h2>NOTES
<a name="NOTES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">Glibc does not
provide a wrapper function for this system call. You could
invoke it using <b>syscall</b>(2). But instead, you probably
want to use the <b>io_getevents</b>() wrapper function
provided by <i>libaio</i>.</p>
<p style="margin-left:11%; margin-top: 1em">Note that the
<i>libaio</i> wrapper function uses a different type
(<i>io_context_t</i>) for the <i>ctx_id</i> argument. Note
also that the <i>libaio</i> 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 <b>syscall</b>(2), then the return value follows the
usual conventions for indicating an error: -1, with
<i>errno</i> set to a (positive) value that indicates the
error.</p>
<h2>BUGS
<a name="BUGS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">An invalid
<i>ctx_id</i> may cause a segmentation fault instead of
generating the error <b>EINVAL</b>.</p>
<h2>SEE ALSO
<a name="SEE ALSO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>io_cancel</b>(2),
<b>io_destroy</b>(2), <b>io_setup</b>(2),
<b>io_submit</b>(2), <b>aio</b>(7), <b>time</b>(7)</p>
<h2>COLOPHON
<a name="COLOPHON"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">This page is
part of release 5.02 of the Linux <i>man-pages</i> 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/.</p>
<hr>
</body>
</html>