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time.html
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<!-- Creator : groff version 1.22.4 -->
<!-- CreationDate: Wed Jan 29 11:26:27 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>TIME</title>
</head>
<body>
<h1 align="center">TIME</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="#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">time - get time
in seconds</p>
<h2>SYNOPSIS
<a name="SYNOPSIS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>#include
<time.h></b></p>
<p style="margin-left:11%; margin-top: 1em"><b>time_t
time(time_t *</b><i>tloc</i><b>);</b></p>
<h2>DESCRIPTION
<a name="DESCRIPTION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>time</b>()
returns the time as the number of seconds since the Epoch,
1970-01-01 00:00:00 +0000 (UTC).</p>
<p style="margin-left:11%; margin-top: 1em">If <i>tloc</i>
is non-NULL, the return value is also stored in the memory
pointed to by <i>tloc</i>.</p>
<h2>RETURN VALUE
<a name="RETURN VALUE"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">On success, the
value of time in seconds since the Epoch is returned. On
error, <i>((time_t) -1)</i> is returned, and
<i>errno</i> is set appropriately.</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"><i>tloc</i> points outside your
accessible address space (but see BUGS).</p></td></tr>
</table>
<p style="margin-left:22%; margin-top: 1em">On systems
where the C library <b>time</b>() wrapper function invokes
an implementation provided by the <b>vdso</b>(7) (so that
there is no trap into the kernel), an invalid address may
instead trigger a <b>SIGSEGV</b> signal.</p>
<h2>CONFORMING TO
<a name="CONFORMING TO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">SVr4, 4.3BSD,
C89, C99, POSIX.1-2001. POSIX does not specify any error
conditions.</p>
<h2>NOTES
<a name="NOTES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">POSIX.1 defines
<i>seconds since the Epoch</i> using a formula that
approximates the number of seconds between a specified time
and the Epoch. This formula takes account of the facts that
all years that are evenly divisible by 4 are leap years, but
years that are evenly divisible by 100 are not leap years
unless they are also evenly divisible by 400, in which case
they are leap years. This value is not the same as the
actual number of seconds between the time and the Epoch,
because of leap seconds and because system clocks are not
required to be synchronized to a standard reference. The
intention is that the interpretation of seconds since the
Epoch values be consistent; see POSIX.1-2008 Rationale
A.4.15 for further rationale.</p>
<p style="margin-left:11%; margin-top: 1em">On Linux, a
call to <b>time</b>() with <i>tloc</i> specified as NULL
cannot fail with the error <b>EOVERFLOW</b>, even on ABIs
where <i>time_t</i> is a signed 32-bit integer and the clock
ticks past the time 2**31 (2038-01-19 03:14:08 UTC, ignoring
leap seconds). (POSIX.1 permits, but does not require, the
<b>EOVERFLOW</b> error in the case where the seconds since
the Epoch will not fit in <i>time_t</i>.) Instead, the
behavior on Linux is undefined when the system time is out
of the <i>time_t</i> range. Applications intended to run
after 2038 should use ABIs with <i>time_t</i> wider than 32
bits.</p>
<h2>BUGS
<a name="BUGS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">Error returns
from this system call are indistinguishable from successful
reports that the time is a few seconds <i>before</i> the
Epoch, so the C library wrapper function never sets
<i>errno</i> as a result of this call.</p>
<p style="margin-left:11%; margin-top: 1em">The <i>tloc</i>
argument is obsolescent and should always be NULL in new
code. When <i>tloc</i> is NULL, the call cannot fail.</p>
<p style="margin-left:11%; margin-top: 1em"><b>C
library/kernel differences</b> <br>
On some architectures, an implementation of <b>time</b>() is
provided in the <b>vdso</b>(7).</p>
<h2>SEE ALSO
<a name="SEE ALSO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>date</b>(1),
<b>gettimeofday</b>(2), <b>ctime</b>(3), <b>ftime</b>(3),
<b>time</b>(7), <b>vdso</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>