160 lines
5.6 KiB
HTML
160 lines
5.6 KiB
HTML
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<title><sys/select.h></title>
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<basefont size="3"> <a name="<sys/select.h>"></a> <a name="tag_13_58"></a><!-- <sys/select.h> -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_13_58_01"></a>NAME</h4>
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<blockquote>sys/select.h - select types</blockquote>
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<h4><a name="tag_13_58_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><tt>#include <sys/select.h></tt></p>
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</blockquote>
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<h4><a name="tag_13_58_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i><sys/select.h></i> header shall define the <b>timeval</b> structure that includes at least the following
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members:</p>
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<pre>
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<tt>time_t tv_sec </tt> Seconds. <tt>
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suseconds_t tv_usec </tt> Microseconds. <tt>
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</tt>
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</pre>
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<p>The <b>time_t</b> and <b>suseconds_t</b> types shall be defined as described in <a href=
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"../sys/types.h.html#tag_13_67"><i><sys/types.h></i></a> .</p>
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<p>The <b>sigset_t</b> type shall be defined as described in <a href="../signal.h.html#"><i><signal.h></i></a> .</p>
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<p>The <b>timespec</b> structure shall be defined as described in <a href="time.h.html"><i><time.h></i></a> .</p>
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<p>The <i><sys/select.h></i> header shall define the <b>fd_set</b> type as a structure.</p>
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<p>Each of the following may be declared as a function, or defined as a macro, or both:</p>
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<dl compact>
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<dt><b>void</b> <i>FD_CLR</i>(<b>int</b> <i>fd</i>, <b>fd_set *</b><i>fdset</i>)</dt>
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<dd><br>
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Clears the bit for the file descriptor <i>fd</i> in the file descriptor set <i>fdset</i>.</dd>
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<dt><b>int</b> <i>FD_ISSET</i>(<b>int</b> <i>fd</i>, <b>fd_set *</b><i>fdset</i>)</dt>
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<dd><br>
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Returns a non-zero value if the bit for the file descriptor <i>fd</i> is set in the file descriptor set by <i>fdset</i>, and 0
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otherwise.</dd>
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<dt><b>void</b> <i>FD_SET</i>(<b>int</b> <i>fd</i>, <b>fd_set *</b><i>fdset</i>)</dt>
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<dd><br>
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Sets the bit for the file descriptor <i>fd</i> in the file descriptor set <i>fdset</i>.</dd>
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<dt><b>void</b> <i>FD_ZERO</i>(<b>fd_set *</b><i>fdset</i>)</dt>
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<dd><br>
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Initializes the file descriptor set <i>fdset</i> to have zero bits for all file descriptors.</dd>
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</dl>
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<p>If implemented as macros, these may evaluate their arguments more than once, so applications should ensure that the arguments
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they supply are never expressions with side effects.</p>
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<p>The following shall be defined as a macro:</p>
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<dl compact>
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<dt>FD_SETSIZE</dt>
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<dd><br>
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Maximum number of file descriptors in an <b>fd_set</b> structure.</dd>
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</dl>
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<p>The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.</p>
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<pre>
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<tt>int pselect(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
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const struct timespec *restrict, const sigset_t *restrict);
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int select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
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struct timeval *restrict);
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</tt>
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</pre>
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<p>Inclusion of the <i><sys/select.h></i> header may make visible all symbols from the headers <a href=
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"../../basedefs/signal.h.html"><i><signal.h></i></a>, <a href="../../basedefs/sys/time.h.html"><i><sys/time.h></i></a>,
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and <a href="../../basedefs/time.h.html"><i><time.h></i></a>.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_13_58_04"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_13_58_05"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_13_58_06"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_13_58_07"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="../signal.h.html#"><i><signal.h></i></a> , <a href="../sys/time.h.html#tag_13_64"><i><sys/time.h></i></a> ,
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<a href="../sys/types.h.html#tag_13_67"><i><sys/types.h></i></a> , <a href="time.h.html"><i><time.h></i></a> , the
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System Interfaces volume of IEEE Std 1003.1-2001, <a href="../../functions/pselect.html"><i>pselect</i>()</a>, <a href=
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"../../functions/select.html"><i>select</i>()</a></p>
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</blockquote>
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<h4><a name="tag_13_58_08"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from IEEE Std 1003.1g-2000.</p>
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<p>The requirement for the <b>fd_set</b> structure to have a member <i>fds_bits</i> has been removed as per The Open Group Base
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Resolution bwg2001-005.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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