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<html><head><title>PerlIO (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_169.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_171.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.170. PerlIO</h2><p><a name="INDEX-1527" />An on-demand loader for PerlIO layersand the root of the PerlIO namespace. PerlIO allows you to expand thefunctionality of <tt class="literal">open()</tt>. For example:</p><blockquote><pre class="code">use PerlIO 'special';</pre></blockquote><p>The code in <em class="filename">PerlIO.pm</em> then attempts to find<tt class="literal">'special</tt>':</p><blockquote><pre class="code">require PerlIO::special;</pre></blockquote><p>PerlIO currently defines the following layers:</p><dl><dt><b><tt class="literal">unix</tt></b></dt><dd>Low-level layer that calls <tt class="literal">read</tt>,<tt class="literal">write</tt>, <tt class="literal">lseek</tt>, etc.</p></dd><dt><b><tt class="literal">stdio</tt></b></dt><dd>Calls <tt class="literal">fread</tt>, <tt class="literal">fwrite</tt>,<tt class="literal">fseek</tt>, <tt class="literal">ftell</tt>, etc.<tt class="literal">stdio</tt> will use your operatingsystem's I/O via the C library. That is, you cannotplace any layers beneath <tt class="literal">stdio</tt>.</p></dd><dt><b><tt class="literal">perlio</tt></b></dt><dd>A reimplementation of a <tt class="literal">stdio</tt>-like bufferingwritten as a PerlIO layer. As such, it will call whatever layer isbelow it for its operations.</p></dd><dt><b><tt class="literal">crlf</tt></b></dt><dd>Does CRLF translation depending on distinguishing text, and binaryfiles a la MS-DOS.</p></dd><dt><b><tt class="literal">utf8</tt></b></dt><dd>Declares that the stream accepts Perl's internalencoding of characters (which is really <tt class="literal">UTF-8</tt> onASCII machines and <tt class="literal">UTF-EBCDIC</tt> on EBCDIC machines).This allows any character Perl can represent to be read from orwritten to the stream. The<tt class="literal">UTF-</tt><em class="replaceable"><tt>X</tt></em> encoding ischosen to render simple text parts (i.e., nonaccented letters,digits, and common punctuation) human-readable in the encoded file.</p></dd><dt><b><tt class="literal">raw</tt></b></dt><dd>A pseudo-layer that performs two functions. It forces the filehandleto be considered binary at that point in the layer stack, and itprevents the I/O system from searching before it in the layerspecification. For example:</p><blockquote><pre class="code">open($fh,":raw:perlio",...);</pre></blockquote><p><tt class="literal">raw</tt> forces the use of the<tt class="literal">perlio</tt> layer even if the platform default or the<tt class="literal">use open</tt> default is something else (such as<tt class="literal">:encoding(iso-8859-7</tt>)).</p></dd></dl><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_169.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_171.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.169. overload</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">8.171. PerlIO::Scalar</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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