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<pre> <span class="headline">sys_time.h(0P)            POSIX Pro‐
grammer’s  Manual            sys_time.h(0P)</span>  </pre> <h2><a
id="PROLOG" href="#PROLOG"></a>PROLOG  &nbsp; &nbsp; &nbsp;  &nb‐
sp;        <a        href="#top_of_page"><span        class="top‐
link">top</span></a></h2><pre>
       This manual page is part of the POSIX Programmer’s Manual.
The Linux
       implementation of this interface may differ (consult the
       corresponding  Linux  manual page for details of Linux be‐
havior), or
       the interface may not be  implemented  on  Linux.   </pre>
<h2><a id="NAME" href="#NAME"></a>NAME  &nbsp; &nbsp; &nbsp; &nb‐
sp;        <a        href="#top_of_page"><span        class="top‐
link">top</span></a></h2><pre>
       sys/time.h   —  time  types  </pre>  <h2><a  id="SYNOPSIS"
href="#SYNOPSIS"></a>SYNOPSIS  &nbsp;  &nbsp;  &nbsp;  &nbsp;  <a
href="#top_of_page"><span                             class="top‐
link">top</span></a></h2><pre>
       #include &lt;sys/time.h&gt; </pre> <h2><a id="DESCRIPTION"
href="#DESCRIPTION"></a>DESCRIPTION   &nbsp; &nbsp; &nbsp; &nbsp;
<a             href="#top_of_page"><span              class="top‐
link">top</span></a></h2><pre>
       The  <i>&lt;sys/time.h&gt;</i>  header  shall  define  the
<b>timeval </b>structure, which
       shall include at least the following members:

           <b>time_t         tv_sec      </b>Seconds.
           suseconds_t    tv_usec     Microseconds.

       The  <i>&lt;sys/time.h&gt;</i>  header  shall  define  the
<b>itimerval </b>structure, which
       shall include at least the following members:

           <b>struct timeval it_interval </b>Timer interval.
           struct timeval it_value    Current value.

       The  <i>&lt;sys/time.h&gt;</i>  header  shall  define  the
<b>time_t </b>and <b>suseconds_t </b>types
       as described in <i>&lt;sys/types.h&gt;</i>.

       The  <i>&lt;sys/time.h&gt;</i>  header  shall  define  the
<b>fd_set </b>type as described in
       <i>&lt;sys/select.h&gt;</i>.

       The <i>&lt;sys/time.h&gt;</i> header shall define the fol‐
lowing symbolic constants
       for the <i>which</i> argument  of  <i>getitimer</i>()  and
<i>setitimer</i>():

       ITIMER_REAL   Decrements in real time.

       ITIMER_VIRTUAL
                     Decrements in process virtual time.

       ITIMER_PROF    Decrements both in process virtual time and
when the
                     system is running on behalf of the process.

       The <i>&lt;sys/time.h&gt;</i> header shall define the fol‐
lowing as described in
       <i>&lt;sys/select.h&gt;</i>:   <i>FD_CLR</i>()   <i>FD_IS‐
SET</i>() <i>FD_SET</i>() <i>FD_ZERO</i>() FD_SETSIZE

       The following shall be declared as functions and may  also
be defined
       as macros. Function prototypes shall be provided.

           <b>int   getitimer(int, struct itimerval *);</b>
           <b>int    gettimeofday(struct  timeval *restrict, void
*restrict);</b>
           <b>int   setitimer(int, const  struct  itimerval  *re‐
strict,</b>
                     <b>struct itimerval *restrict);</b>
           <b>int    select(int,  fd_set  *restrict,  fd_set *re‐
strict, fd_set *restrict,</b>
                     <b>struct timeval *restrict);</b>
           <b>int   utimes(const char  *,  const  struct  timeval
[2]);</b>

       Inclusion of the <i>&lt;sys/time.h&gt;</i> header may make
visible all symbols
       from the <i>&lt;sys/select.h&gt;</i> header.

       <i>The  following  sections  are  informative.</i>  </pre>
<h2><a  id="APPLICATION_USAGE"  href="#APPLICATION_USAGE"></a>AP‐
PLICATION    USAGE     &nbsp;    &nbsp;    &nbsp;    &nbsp;    <a
href="#top_of_page"><span                             class="top‐
link">top</span></a></h2><pre>
       None.    </pre>   <h2><a   id="RATIONALE"    href="#RATIO‐
NALE"></a>RATIONALE     &nbsp;    &nbsp;    &nbsp;    &nbsp;   <a
href="#top_of_page"><span                             class="top‐
link">top</span></a></h2><pre>
       None.   </pre>  <h2><a  id="FUTURE_DIRECTIONS"  href="#FU‐
TURE_DIRECTIONS"></a>FUTURE DIRECTIONS  &nbsp; &nbsp; &nbsp; &nb‐
sp;        <a        href="#top_of_page"><span        class="top‐
link">top</span></a></h2><pre>
       None.    </pre>   <h2><a   id="SEE_ALSO"    href="#SEE_AL‐
SO"></a>SEE    ALSO     &nbsp;    &nbsp;    &nbsp;    &nbsp;   <a
href="#top_of_page"><span                             class="top‐
link">top</span></a></h2><pre>
       <a             href="../man0/sys_select.h.0p.html">sys_se‐
lect.h(0p)</a>,                                                <a
href="../man0/sys_types.h.0p.html">sys_types.h(0p)</a>

       The   System   Interfaces   volume   of  POSIX.1‐2008,  <a
href="../man3/futimens.3p.html">futimens(3p)</a>,
       <a href="../man3/getitimer.3p.html">getitimer(3p)</a>,  <a
href="../man3/gettimeofday.3p.html">gettimeofday(3p)</a>,      <a
href="../man3/pselect.3p.html">pselect(3p)</a>   </pre>    <h2><a
id="COPYRIGHT"   href="#COPYRIGHT"></a>COPYRIGHT   &nbsp;  &nbsp;
&nbsp;   &nbsp;    <a    href="#top_of_page"><span    class="top‐
link">top</span></a></h2><pre>
       Portions  of  this  text  are  reprinted and reproduced in
electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for  Informa‐
tion
       Technology ‐‐ Portable Operating System Interface (POSIX),
The Open
       Group Base Specifications Issue 7, Copyright (C)  2013  by
the
       Institute of Electrical and Electronics Engineers, Inc and
The Open
       Group.  (This is POSIX.1‐2008 with the 2013 Technical Cor‐
rigendum 1
       applied.)  In  the  event  of any discrepancy between this
version and
       the original IEEE and The Open Group Standard, the  origi‐
nal IEEE and
       The Open Group Standard is the referee document. The orig‐
inal
       Standard    can    be    obtained     online     at     <a
href="http://www.unix.org/online.html">http://www.unix.org/on‐
line.html</a> .

       Any typographical or formatting errors that appear in this
page are
       most  likely to have been introduced during the conversion
of the
       source files to man page format. To  report  such  errors,
see
       <a      href="https://www.kernel.org/doc/man‐pages/report‐
ing_bugs.html">https://www.kernel.org/doc/man‐pages/report‐
ing_bugs.html</a> .

<span  class="footline">IEEE/The  Open Group                 2013
sys_time.h(0P)</span> </pre>

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