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<html><head><title>A Pattern Test Program (Learning Perl, 3rd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Randal L. Schwartz and Tom Phoenix" /><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="0596001320L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Learning Perl, 3rd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Learning Perl, 3rd Edition" /><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="ch07_02.htm"><img alt="Previous" border="0" src="../gifs/txtpreva.gif" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"></a></td><td align="right" valign="top" width="228"><a href="ch07_04.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr></table></div><h2 class="sect1">7.3. A Pattern Test Program</h2><p><a name="INDEX-518" />When in the course of Perl events itbecomes necessary for a programmer to write a regular expression, itmay be difficult to tell just what the pattern will do. It'snormal to find that a pattern matches more than you expected, orless. Or it may match earlier in the string than you expected, orlater, or not at all.</p><p>This program is useful to test out a pattern on some strings and seejust what it matches, and where:</p><blockquote><pre class="code">#!/usr/bin/perlwhile (<>) { # take one input line at a time chomp; if (/YOUR_PATTERN_GOES_HERE/) { print "Matched: |$`<$&>$'|\n"; # Mystery code! See the text. } else { print "No match.\n"; }}</pre></blockquote><p>This pattern test program is written for programmers to use, notendusers; you can tell because it doesn't have any prompts orusage information. It will take any number of input lines and checkeach one against the pattern that you'll put in place of thestring saying <tt class="literal">YOUR_PATTERN_GOES_HERE</tt>. For eachline that matches, the line with "mystery code" will berun. We'll learn about what that line is really doing in <a href="ch09_01.htm">Chapter 9, "Using Regular Expressions"</a>. But what you'll see is this: if thepattern is <tt class="literal">/match/</tt> and the input is<tt class="literal">beforematchafter</tt>, the output will say"<tt class="literal">|before<match>after|</tt>", using<a name="INDEX-519" /><a name="INDEX-520" />angle brackets toshow you just what part of the string was matched by your pattern.Try it and see! If you pattern matches something you didn'texpect, you'll be able to see that right<a name="INDEX-521" /> away.<a name="INDEX-522" /></p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch07_02.htm"><img alt="Previous" border="0" src="../gifs/txtpreva.gif" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img alt="Home" border="0" src="../gifs/txthome.gif" /></a></td><td align="right" valign="top" width="228"><a href="ch07_04.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr><tr><td align="left" valign="top" width="228">7.2. Using Simple Patterns</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img alt="Book Index" border="0" src="../gifs/index.gif" /></a></td><td align="right" valign="top" width="228">7.4. Exercises</td></tr></table></div><hr width="684" align="left" /><img alt="Library Navigation Links" border="0" src="../gifs/navbar.gif" usemap="#library-map" /><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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