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<html><head><title>Fatal (Programming Perl)</title><!-- STYLESHEET --><link rel="stylesheet" type="text/css" href="../style/style1.css"><!-- METADATA --><!--Dublin Core Metadata--><meta name="DC.Creator" content=""><meta name="DC.Date" content=""><meta name="DC.Format" content="text/xml" scheme="MIME"><meta name="DC.Generator" content="XSLT stylesheet, xt by James Clark"><meta name="DC.Identifier" content=""><meta name="DC.Language" content="en-US"><meta name="DC.Publisher" content="O'Reilly & Associates, Inc."><meta name="DC.Source" content="" scheme="ISBN"><meta name="DC.Subject.Keyword" content=""><meta name="DC.Title" content="Fatal"><meta name="DC.Type" content="Text.Monograph"></head><body><!-- START OF BODY --><!-- TOP BANNER --><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home"><map name="banner-map"><AREA SHAPE="RECT" COORDS="0,0,466,71" HREF="index.htm" ALT="Programming Perl"><AREA SHAPE="RECT" COORDS="467,0,514,18" HREF="jobjects/fsearch.htm" ALT="Search this book"></map><!-- TOP NAV BAR --><div class="navbar"><table width="515" border="0"><tr><td align="left" valign="top" width="172"><a href="ch32_15.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="ch32_01.htm">Chapter 32: Standard Modules</a></td><td align="right" valign="top" width="172"><a href="ch32_17.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr></table></div><hr width="515" align="left"><!-- SECTION BODY --><h2 class="sect1">32.16. Fatal</h2><p>The <tt class="literal">Fatal</tt> module makes functions fail morespectacularly. It replaces functions that normally return falseupon failure with wrappers that raise an exception if the realfunction returns false. That way you can safely use these functionswithout testing their return values explicitly on each call.</p><p>Both user-defined functions and built-in functions may be wrapped,except for those built-ins that cannot be expressed via prototypes.Attempting to override a nonoverridable built-in raises an exception.These include <tt class="literal">system</tt>, <tt class="literal">print</tt>, <tt class="literal">printf</tt>, <tt class="literal">exec</tt>, <tt class="literal">split</tt>,<tt class="literal">grep</tt>, and <tt class="literal">map</tt>--or more generally, any <em class="replaceable">FUNC</em> for which<tt class="literal">prototype "CORE::</tt><em class="replaceable">FUNC</em><tt class="literal">"</tt> returns false, including the<tt class="literal">prototype</tt> function itself.</p><p>If the symbol <tt class="literal">:void</tt> appears in the import list, functions namedlater in the list are limited to raising an exception when the functionis called in void context--that is, when the return value is ignored.(Be careful about the last statement in a subroutine.) For example:<blockquote><pre class="programlisting">use Fatal qw(:void open close);# open properly checked, so no exception is raised on failure.if (open(FH, "< /nonesuch") { warn "no /nonesuch: $!"; }# close not properly checked, so failure raises an exception.close FH;</pre></blockquote></p><!-- BOTTOM NAV BAR --><hr width="515" align="left"><div class="navbar"><table width="515" border="0"><tr><td align="left" valign="top" width="172"><a href="ch32_15.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0"></a></td><td align="center" valign="top" width="171"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0"></a></td><td align="right" valign="top" width="172"><a href="ch32_17.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0"></a></td></tr><tr><td align="left" valign="top" width="172">32.15. Exporter</td><td align="center" valign="top" width="171"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0"></a></td><td align="right" valign="top" width="172">32.17. Fcntl</td></tr></table></div><hr width="515" align="left"><!-- LIBRARY NAV BAR --><img src="../gifs/smnavbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links"><p><font size="-1"><a href="copyrght.htm">Copyright © 2001</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"> <area shape="rect" coords="2,-1,79,99" href="../index.htm"><area shape="rect" coords="84,1,157,108" href="../perlnut/index.htm"><area shape="rect" coords="162,2,248,125" href="../prog/index.htm"><area shape="rect" coords="253,2,326,130" href="../advprog/index.htm"><area shape="rect" coords="332,1,407,112" href="../cookbook/index.htm"><area shape="rect" coords="414,2,523,103" href="../sysadmin/index.htm"></map><!-- END OF BODY --></body></html>⌨️ 快捷键说明
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