time.h.html

IEEE 1003.1-2003, Single Unix Specification v3

struct tm *gmtime_r(const time_t *restrict, struct tm *restrict);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
struct tm *localtime(const time_t *);
<sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
struct tm *localtime_r(const time_t *restrict, struct tm *restrict);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
time_t     mktime(struct tm *);
<sup>[<a href="javascript:open_code('TMR')">TMR</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int        nanosleep(const struct timespec *, struct timespec *);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
size_t     strftime(char *restrict, size_t, const char *restrict,
           const struct tm *restrict);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
char      *strptime(const char *restrict, const char *restrict,
               struct tm *restrict);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
time_t     time(time_t *);
<sup>[<a href="javascript:open_code('TMR')">TMR</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
int        timer_create(clockid_t, struct sigevent *restrict,
               timer_t *restrict);
int        timer_delete(timer_t);
int        timer_gettime(timer_t, struct itimerspec *);
int        timer_getoverrun(timer_t);
int        timer_settime(timer_t, int, const struct itimerspec *restrict,
               struct itimerspec *restrict);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
<sup>[<a href="javascript:open_code('CX')">CX</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
void       tzset(void);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
</tt>
</pre>

<br>
<p>The following shall be declared as variables:</p>

<pre>
<tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
extern int    daylight;
extern long   timezone;
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
<sup>[<a href="javascript:open_code('CX')">CX</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
extern char  *tzname[];
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
</tt>
</pre>

<p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Inclusion of the <i>&lt;time.h&gt;</i> header may make visible all symbols from the <a href=
"../basedefs/signal.h.html"><i>&lt;signal.h&gt;</i></a> header. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
</blockquote>

<hr>
<div class="box"><em>The following sections are informative.</em></div>

<h4><a name="tag_13_76_04"></a>APPLICATION USAGE</h4>

<blockquote>
<p>The range [0,60] for <i>tm_sec</i> allows for the occasional leap second.</p>

<p><i>tm_year</i> is a signed value; therefore, years before 1900 may be represented.</p>

<p>To obtain the number of clock ticks per second returned by the <a href="../functions/times.html"><i>times</i>()</a> function,
applications should call <i>sysconf</i>(_SC_CLK_TCK).</p>
</blockquote>

<h4><a name="tag_13_76_05"></a>RATIONALE</h4>

<blockquote>
<p>The range [0,60] seconds allows for positive or negative leap seconds. The formal definition of UTC does not permit double leap
seconds, so all mention of double leap seconds has been removed, and the range shortened from the former [0,61] seconds seen in
previous versions of POSIX.</p>
</blockquote>

<h4><a name="tag_13_76_06"></a>FUTURE DIRECTIONS</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_13_76_07"></a>SEE ALSO</h4>

<blockquote>
<p><a href="signal.h.html"><i>&lt;signal.h&gt;</i></a> , <a href="sys/types.h.html"><i>&lt;sys/types.h&gt;</i></a> , the System
Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href="../functions/asctime.html"><i>asctime</i>()</a>, <a href=
"../functions/clock.html"><i>clock</i>()</a>, <a href="../functions/clock_getcpuclockid.html"><i>clock_getcpuclockid</i>()</a>, <a
href="../functions/clock_getres.html"><i>clock_getres</i>()</a>, <a href=
"../functions/clock_nanosleep.html"><i>clock_nanosleep</i>()</a>, <a href="../functions/ctime.html"><i>ctime</i>()</a>, <a href=
"../functions/difftime.html"><i>difftime</i>()</a>, <a href="../functions/getdate.html"><i>getdate</i>()</a>, <a href=
"../functions/gmtime.html"><i>gmtime</i>()</a>, <a href="../functions/localtime.html"><i>localtime</i>()</a>, <a href=
"../functions/mktime.html"><i>mktime</i>()</a>, <a href="../functions/nanosleep.html"><i>nanosleep</i>()</a>, <a href=
"../functions/strftime.html"><i>strftime</i>()</a>, <a href="../functions/strptime.html"><i>strptime</i>()</a>, <a href=
"../functions/sysconf.html"><i>sysconf</i>()</a>, <a href="../functions/time.html"><i>time</i>()</a>, <a href=
"../functions/timer_create.html"><i>timer_create</i>()</a>, <a href="../functions/timer_delete.html"><i>timer_delete</i>()</a>, <a
href="../functions/timer_getoverrun.html"><i>timer_getoverrun</i>()</a>, <i>tzname</i>, <a href=
"../functions/tzset.html"><i>tzset</i>()</a>, <a href="../functions/utime.html"><i>utime</i>()</a></p>
</blockquote>

<h4><a name="tag_13_76_08"></a>CHANGE HISTORY</h4>

<blockquote>
<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
</blockquote>

<h4><a name="tag_13_76_09"></a>Issue 5</h4>

<blockquote>
<p>The DESCRIPTION is updated for alignment with the POSIX Realtime Extension and the POSIX Threads Extension.</p>
</blockquote>

<h4><a name="tag_13_76_10"></a>Issue 6</h4>

<blockquote>
<p>The Open Group Corrigendum U035/6 is applied. In the DESCRIPTION, the types <b>clockid_t</b> and <b>timer_t</b> have been
described.</p>

<p>The following changes are made for alignment with the ISO&nbsp;POSIX-1:1996 standard:</p>

<ul>
<li>
<p>The POSIX timer-related functions are marked as part of the Timers option.</p>
</li>
</ul>

<p>The symbolic name CLK_TCK is removed. Application usage is added describing how its equivalent functionality can be obtained
using <a href="../functions/sysconf.html"><i>sysconf</i>()</a>.</p>

<p>The <a href="../functions/clock_getcpuclockid.html"><i>clock_getcpuclockid</i>()</a> function and manifest constants
CLOCK_PROCESS_CPUTIME_ID and CLOCK_THREAD_CPUTIME_ID are added for alignment with IEEE&nbsp;Std&nbsp;1003.1d-1999.</p>

<p>The manifest constant CLOCK_MONOTONIC and the <a href="../functions/clock_nanosleep.html"><i>clock_nanosleep</i>()</a> function
are added for alignment with IEEE&nbsp;Std&nbsp;1003.1j-2000.</p>

<p>The following changes are made for alignment with the ISO/IEC&nbsp;9899:1999 standard:</p>

<ul>
<li>
<p>The range for seconds is changed from [0,61] to [0,60].</p>
</li>

<li>
<p>The <b>restrict</b> keyword is added to the prototypes for <a href="../functions/asctime_r.html"><i>asctime_r</i>()</a>, <a
href="../functions/gmtime_r.html"><i>gmtime_r</i>()</a>, <a href="../functions/localtime_r.html"><i>localtime_r</i>()</a>, <a href=
"../functions/strftime.html"><i>strftime</i>()</a>, <a href="../functions/strptime.html"><i>strptime</i>()</a>, <a href=
"../functions/timer_create.html"><i>timer_create</i>()</a>, and <a href=
"../functions/timer_settime.html"><i>timer_settime</i>()</a>.</p>
</li>
</ul>

<p>IEEE PASC Interpretation 1003.1 #84 is applied adding the statement that symbols from the <a href=
"../basedefs/signal.h.html"><i>&lt;signal.h&gt;</i></a> header may be made visible when the <i>&lt;time.h&gt;</i> header is
included.</p>

<p>Extensions beyond the ISO&nbsp;C standard are marked.</p>
</blockquote>

<div class="box"><em>End of informative text.</em></div>

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