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<pre> <span class="headline">poll.h(0P)                POSIX Pro‐
grammer’s  Manual                poll.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>
       poll.h — definitions for the poll() function </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;poll.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;poll.h&gt;</i>   header   shall   define  the
<b>pollfd </b>structure, which shall
       include at least the following members:

           <b>int    fd       </b>The following descriptor  being
polled.
           <b>short   events   </b>The input event flags (see be‐
low).
           <b>short  revents  </b>The output event flags (see be‐
low).

       The  <i>&lt;poll.h&gt;</i> header shall define the follow‐
ing type through <b>typedef</b>:

       <b>nfds_t        </b>An unsigned integer type used for the
number of file
                     descriptors.

       The  implementation  shall support one or more programming
environments
       in which the width of <b>nfds_t </b>is no greater than the
width of type
       <b>long</b>.   The names of these programming environments
can be obtained
       using the <i>confstr</i>() function or the  <i>getconf</i>
utility.

       The  <i>&lt;poll.h&gt;</i> header shall define the follow‐
ing symbolic constants,
       zero or more of which may be OR’ed together  to  form  the
<i>events</i> or
       <i>revents</i> members in the <b>pollfd </b>structure:

       POLLIN         Data  other  than high‐priority data may be
read without
                     blocking.

       POLLRDNORM    Normal data may be read without blocking.

       POLLRDBAND    Priority data may be read without blocking.

       POLLPRI       High  priority  data  may  be  read  without
blocking.

       POLLOUT       Normal data may be written without blocking.

       POLLWRNORM    Equivalent to POLLOUT.

       POLLWRBAND    Priority data may be written.

       POLLERR       An error has occurred (<i>revents</i> only).

       POLLHUP       Device has been disconnected (<i>revents</i>
only).

       POLLNVAL      Invalid <i>fd</i> member (<i>revents</i> on‐
ly).

       The  significance  and  semantics of normal, priority, and
high‐priority
       data are file and device‐specific.

       The following shall be declared as a function and may also
be defined
       as a macro. A function prototype shall be provided.

           <b>int   poll(struct pollfd [], nfds_t, int);</b>

       <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>
       The  System  Interfaces   volume   of   POSIX.1‐2008,   <a
href="../man3/confstr.3p.html">confstr(3p)</a>,                <a
href="../man3/poll.3p.html">poll(3p)</a>

       The  Shell  and  Utilities  volume  of  POSIX.1‐2008,   <a
href="../man1/getconf.1p.html">getconf(1p)</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
poll.h(0P)</span> </pre>

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