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<html><head><title>IO::Select (Perl in a Nutshell, 2nd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Stephen Spainhour" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="0596002416L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl in a Nutshell, 2nd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Java and XSLT" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_130.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch08_132.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.131. IO::Select</h2><p><a name="INDEX-1481" />Implements an object-oriented approachto the system <tt class="literal">select</tt> function call. Allows theuser to see which I/O handles are ready for reading, writing, or havean error condition pending.</p><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>new</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>new $<em class="replaceable">s</em> = IO::Select->new([<em class="replaceable">handles</em>])</pre><p>Constructor. Creates a new object and optionally initializes it witha set of handles.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>add</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->add(<em class="replaceable">handles</em>)</pre><p>Adds list of handles to the IO::Select object, to be returned when anevent occurs. IO::Select keeps the list of handles in a cache, whichis indexed by the handle's file number. Each handlecan be an IO::Handle object, an integer, or a reference to an array,in which the first element is an IO::Handle object or an integer.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>bits</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->bits( )</pre><p>Returns the bit string that is suitable for use as an argument to thecore <tt class="literal">select</tt> call.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>can_read</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->can_read([<em class="replaceable">timeout</em>])</pre><p>Returns array of handles that are ready for reading.<em class="replaceable"><tt>timeout</tt></em> is the maximum amount of time towait before returning an empty list. If<em class="replaceable"><tt>timeout</tt></em> is not given, and any handles areregistered, then the call blocks.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>can_write</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->can_write([<em class="replaceable">timeout</em>])</pre><p>Same as <tt class="literal">can_read</tt>, but checks for handles that canbe written to.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>count</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->count( )</pre><p>Returns the number of handles that the object checks for when one ofthe <tt class="literal">can_</tt> methods is called or the object is passedto the <tt class="literal">select</tt> static method.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>exists</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->exists(<em class="replaceable">handle</em>)</pre><p>Returns the handle if it is present; otherwise, returns<tt class="literal">undef</tt>.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>handles</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->handles</pre><p>Returns an array of all registered handles.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>has_error</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->has_error([<em class="replaceable">timeout</em>])</pre><p>Same as <tt class="literal">can_read</tt>, but checks for handles that havean error condition.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>remove</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->remove(<em class="replaceable">handles</em>)</pre><p>Removes all the given handles from the object, locating them by filenumber.</p></div><div class="refentry"><table width="515" border="0" cellpadding="5"><tr><td align="left"><font size="+1"><b>select</b></font></td><td align="right"><i></i></td></tr></table><hr width="515" size="3" noshade="true" align="left" color="black" /><pre>$<em class="replaceable">s</em>->select(<em class="replaceable">read</em>, <em class="replaceable">write</em>, <em class="replaceable">error</em>[, <em class="replaceable">timeout</em>])</pre><p>Static method. Call it with the package name as with<tt class="literal">new</tt>. <tt class="literal">read</tt>,<tt class="literal">write</tt>, and <tt class="literal">error</tt> are either<tt class="literal">undef</tt> or IO::Select objects. The optional argument<em class="replaceable"><tt>timeout</tt></em> has the same effect as for thecore <tt class="literal">select</tt> call.</p><p>Returns an array of three elements, each a reference to an array oran empty array on error. The arrays hold the handles that are readyfor reading, ready for writing, and have error conditions,respectively.</p></div><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_130.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch08_132.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.130. IO::Seekable</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">8.132. IO::Socket</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"><area shape="rect" coords="1,0,85,94" href="../index.htm"><area shape="rect" coords="86,1,178,103" href="../lwp/index.htm"><area shape="rect" coords="180,0,265,103" href="../lperl/index.htm"><area shape="rect" coords="267,0,353,105" href="../perlnut/index.htm"><area shape="rect" coords="354,1,446,115" href="../prog/index.htm"><area shape="rect" coords="448,0,526,132" href="../tk/index.htm"><area shape="rect" coords="528,1,615,119" href="../cookbook/index.htm"><area shape="rect" coords="617,0,690,135" href="../pxml/index.htm"></map></body></html>⌨️ 快捷键说明
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