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<html><head><title>Metacharacters (UNIX in a Nutshell: System V Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Arnold Robbins" /><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="1-56592-427-4" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="UNIX in a Nutshell: System V 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="Book Title" /><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="ch06_02.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="ch06_04.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">6.3. Metacharacters</h2><a name="unut-ch-6-sect-3.1" /><div class="sect2"><h3 class="sect2">6.3.1. Search Patterns</h3><p>The characters in the following table have special meaning only in search patterns.</p><table border="1" cellpadding="3"><tr><th><em class="emphasis">Character</em></th><th><em class="emphasis">Pattern</em></th></tr><tr><td><tt class="literal">.</tt></td><td><p>Match any <em class="emphasis">single</em> character except newline.Can match newline in <tt class="literal">awk</tt>.<a name="IXT-6-123100" /><a name="IXT-6-123101" /></p></td></tr><tr><td><tt class="literal">*</tt></td><td><p>Match any number (or none) of the single character thatimmediately precedes it. The preceding character can also be a regularexpression; e.g., since <tt class="literal">.</tt> (dot) means any character,<tt class="literal">.*</tt> means “match any number of anycharacter.”<a name="IXT-6-123102" /></p></td></tr><tr><td><tt class="literal">^</tt></td><td><p>Match the following regular expression at the beginning of the lineor string.<a name="IXT-6-123103" /></p></td></tr><tr><td><tt class="literal">$</tt></td><td><p>Match the preceding regular expression at the end of the lineor string.<a name="IXT-6-123104" /></p></td></tr><tr><td><tt class="literal">[ ]</tt></td><td><p>Match any <em class="emphasis">one</em> of the enclosedcharacters.</p><p>A hyphen (<tt class="literal">-</tt>) indicates arange of consecutive<a name="IXT-6-123105" /><a name="IXT-6-123106" />characters. A circumflex (<tt class="literal">^</tt>) as the first character in thebrackets reverses the sense: it matches any one character<em class="emphasis">not</em> in the list. A hyphen or close bracket (<tt class="literal">]</tt>)as the first character is treated as a member of the list. All othermetacharacters are treated as members of the list(i.e., literally).</p></td></tr><tr><td><tt class="literal">{</tt><em class="replaceable"><tt>n</em><tt class="literal">,</tt><em class="replaceable">m</tt></em><tt class="literal">}</tt></td><td><p><a name="IXT-6-123107" />Match a range of occurrences of the single character thatimmediately precedes it. The preceding character can also be a metacharacter.<tt class="literal">{</tt><em class="replaceable"><tt>n</tt></em><tt class="literal">}</tt>matches exactly <em class="emphasis">n</em> occurrences,<tt class="literal">{</tt><em class="replaceable"><tt>n</tt></em><tt class="literal">,}</tt>matches at least <em class="emphasis">n</em> occurrences, and<tt class="literal">{</tt><em class="replaceable"><tt>n</em><tt class="literal">,</tt><em class="replaceable">m</tt></em><tt class="literal">}</tt>matches any number ofoccurrences between <em class="emphasis">n</em> and <em class="emphasis">m</em>. <em class="emphasis">n</em>and <em class="emphasis">m</em> must be between 0 and 255, inclusive.</p></td></tr><tr><td><tt class="literal">\{</tt><em class="replaceable"><tt>n</em><tt class="literal">,</tt><em class="replaceable">m</tt></em><tt class="literal">\}</tt></td><td><p>Just like<tt class="literal">{</tt><em class="replaceable"><tt>n</em><tt class="literal">,</tt><em class="replaceable">m</tt></em><tt class="literal">}</tt>,above, but with backslashes in front of the braces.</p></td></tr><tr><td><tt class="literal">\</tt></td><td>Turn off the special meaning of the character that follows.</td></tr><tr><td><tt class="literal">\( \)</tt></td><td><p><a name="IXT-6-123108" />Save the pattern enclosed between <tt class="literal">\(</tt>and <tt class="literal">\)</tt> into aspecial holding space. Up to nine patterns can be saved on a singleline. The text matched by the subpatternscan be “replayed” in substitutions by the escapesequences <tt class="literal">\1</tt> to <tt class="literal">\9</tt>.</p></td></tr><tr><td><tt class="literal">\</tt><em class="replaceable"><tt>n</em></td><td><p>Replay the <em class="emphasis">n</tt></em>th subpattern enclosed in <tt class="literal">\(</tt>and <tt class="literal">\)</tt> into the pattern at this point.<em class="emphasis">n</em> is a number from 1 to 9, with 1 starting on the left.See the following Examples.</p></td></tr><tr><td><tt class="literal">\< \></tt></td><td><p>Match characters at beginning (<tt class="literal">\<</tt>)or end (<tt class="literal">\></tt>) of a word.</p></td></tr><tr><td><tt class="literal">+</tt></td><td>Match one or more instances of preceding regular expression.</td></tr><tr><td><tt class="literal">?</tt></td><td><p>Match zero or one instances of preceding regular expression.</p></td></tr><tr><td><tt class="literal">|</tt></td><td><p>Match the regular expression specified before or after.</p></td></tr><tr><td><tt class="literal">( )</tt></td><td><p>Apply a match to the enclosed group of regular expressions.</p></td></tr></table><p><p><a name="IXT-6-123109" /><a name="IXT-6-123110" />Many Unix systems allow the use of POSIX “character classes”within the square brackets that enclose a group of characters.These classes, listed here, are typed enclosed in <tt class="literal">[:</tt> and <tt class="literal">:]</tt>.For example, <tt class="literal">[[:alnum:]]</tt> matches a singlealphanumeric character.</p><table border="1" cellpadding="3"><tr><th><em class="emphasis">Class</em></th><th><em class="emphasis">Characters Matched</em></th></tr><tr><td><tt class="literal">alnum</tt></td><td><p>Alphanumeric characters</p></td></tr><tr><td><tt class="literal">alpha</tt></td><td><p>Alphabetic characters</p></td></tr><tr><td><tt class="literal">blank</tt></td><td><p>Space or tab</p></td></tr><tr><td><tt class="literal">cntrl</tt></td><td><p>Control characters</p></td></tr><tr><td><tt class="literal">digit</tt></td><td><p>Decimal digits</p></td></tr><tr><td><tt class="literal">graph</tt></td><td><p>Nonspace characters</p></td></tr><tr><td><tt class="literal">lower</tt></td><td><p>Lowercase characters</p></td></tr><tr><td><tt class="literal">print</tt></td><td><p>Printable characters</p></td></tr><tr><td><tt class="literal">space</tt></td><td><p>Whitespace characters</p></td></tr><tr><td><tt class="literal">upper</tt></td><td><p>Uppercase characters</p></td></tr><tr><td><tt class="literal">xdigit</tt></td><td><p>Hexadecimal digits</p></td></tr></table><p></div><a name="unut-ch-6-sect-3.2" /><div class="sect2"><h3 class="sect2">6.3.2. Replacement Patterns</h3><p>The characters in this table have special meaning only in replacementpatterns.</p><table border="1" cellpadding="3"><tr><th><em class="emphasis">Character</em></th><th><em class="emphasis">Pattern</em></th></tr><tr><td><tt class="literal">\</tt></td><td><p>Turn off the special meaning of the character that follows.</p></td></tr><tr><td><tt class="literal">\</tt><em class="replaceable"><tt>n</em></td><td><p>Restore the text matched by the <em class="emphasis">n</tt></em>th pattern previously saved by<tt class="literal">\(</tt> and <tt class="literal">\)</tt>.<em class="emphasis">n</em> is a number from 1 to 9, with 1 starting on the left.</p></td></tr><tr><td><tt class="literal">&</tt></td><td><p>Reuse the text matched by the search pattern as part of the replacement pattern.<a name="IXT-6-123111" /></p></td></tr><tr><td><tt class="literal">~</tt></td><td><p><a name="IXT-6-123112" />Reuse the previous replacement pattern in the current replacement pattern.Must be the only character in the replacement pattern.(<tt class="literal">ex</tt> and <tt class="literal">vi</tt>)</p></td></tr><tr><td><tt class="literal">%</tt></td><td><p><a name="IXT-6-123113" />Reuse the previous replacement pattern in the current replacement pattern.Must be the only character in the replacement pattern.(<tt class="literal">ed</tt>)</p></td></tr><tr><td><tt class="literal">\u</tt></td><td><p>Convert first character of replacement pattern to uppercase.</p></td></tr><tr><td><tt class="literal">\U</tt></td><td><p>Convert entire replacement pattern to uppercase.</p></td></tr><tr><td><tt class="literal">\l</tt></td><td><p>Convert first character of replacement pattern to lowercase.</p></td></tr><tr><td><tt class="literal">\L</tt></td><td><p>Convert entire replacement pattern to lowercase.</p></td></tr><tr><td><tt class="literal">\e, \E</tt></td><td><p>Turn off previous <tt class="literal">\u</tt>,<tt class="literal">\U</tt>, <tt class="literal">\l</tt>, and <tt class="literal">\L</tt>.</p></td></tr></table><p><a name="IXT-6-123114" /></div><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch06_02.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="ch06_04.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">6.2. Metacharacters, Listed by Unix Program</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">6.4. Examples of Searching</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 © 2003</a> O'Reilly & Associates. 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