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<html><head><title>General Quantifiers (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="ch08_01.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="ch08_03.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr></table></div><h2 class="sect1">8.2. General Quantifiers</h2><p>A<em class="firstterm">quantifier</em><a name="INDEX-544" />in a pattern means to repeat the preceding item a certain number oftimes. We've already seen three quantifiers:<tt class="literal">*</tt>, <tt class="literal">+</tt>, and <tt class="literal">?</tt>.But if none of those three suits your needs, just use a<a name="INDEX-545" />comma-separatedpair of numbers inside <a name="INDEX-546" />curly braces(<tt class="literal">{}</tt>) to specify exactly how few and how manyrepetitions are allowed.</p><p>So the pattern <tt class="literal">/a{5,15}/</tt> will match from five tofifteen repetitions of the letter <tt class="literal">a</tt>. If the<tt class="literal">a</tt> appears three times, that's too few, so itwon't match. If it appears five times, it's a match. Ifit appears ten times, that's still a match. If it appearstwenty times, just the first fifteen will match, since that'sthe upper limit.</p><p>If you omit the second number (but include the comma), there'sno upper limit to the number of times the item will match. So,<tt class="literal">/(fred){3,}/</tt> will match if there are three or moreinstances of <tt class="literal">fred</tt> in a row (with no extracharacters, like spaces, allowed between each <tt class="literal">fred</tt>and the next). There's no upper limit, so that would matcheighty-eight instances of <tt class="literal">fred</tt>, if you had astring with that many.</p><p>If you omit the comma as well as the upper bound, the number given isan exact count: <tt class="literal">/\w{8}/</tt> will match exactly eightword characters (occuring as part of a larger string, perhaps).</p><p>In fact, the three quantifier characters that we saw earlier are justcommon shortcuts. The star is the same as the quantifier<tt class="literal">{0,}</tt>, meaning zero or more. The plus is the sameas <tt class="literal">{1,}</tt>, meaning one or more. And the questionmark could be written as <tt class="literal">{0,1}</tt>. In practice,it's unusual to need any curly-brace quantifiers, since thethree shortcut characters are nearly always the only ones needed.</p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_01.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="ch08_03.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr><tr><td align="left" valign="top" width="228">8. More About Regular Expressions</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">8.3. Anchors</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. 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