<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head profile="http://internetalchemy.org/2003/02/profile">
<link rel="foaf" type="application/rdf+xml" title="FOAF" href="http://www.openlinksw.com/dataspace/uda/about.rdf" />
<link rel="schema.dc" href="http://purl.org/dc/elements/1.1/" />
<meta name="dc.title" content="21. Appendix" />
<meta name="dc.subject" content="21. Appendix" />
<meta name="dc.creator" content="OpenLink Software Documentation Team ; " />
<meta name="dc.copyright" content="OpenLink Software, 1999 - 2009" />
<link rel="top" href="index.html" title="OpenLink Virtuoso Universal Server: Documentation" />
<link rel="search" href="/doc/adv_search.vspx" title="Search OpenLink Virtuoso Universal Server: Documentation" />
<link rel="parent" href="appendixa.html" title="Chapter Contents" />
<link rel="prev" href="systemtables.html" title="Virtuoso System Tables" />
<link rel="next" href="apndxclientcompilance.html" title="Server & client versions compatibility" />
<link rel="shortcut icon" href="../images/misc/favicon.ico" type="image/x-icon" />
<link rel="stylesheet" type="text/css" href="doc.css" />
<link rel="stylesheet" type="text/css" href="/doc/translation.css" />
<title>21. Appendix</title>
<meta http-equiv="Content-Type" content="text/xhtml; charset=UTF-8" />
<meta name="author" content="OpenLink Software Documentation Team ; " />
<meta name="copyright" content="OpenLink Software, 1999 - 2009" />
<meta name="keywords" content="" />
<meta name="GENERATOR" content="OpenLink XSLT Team" />
</head>
<body>
<div id="header">
<a name="apndxregexp" />
<img src="../images/misc/logo.jpg" alt="" />
<h1>21. Appendix</h1>
</div>
<div id="navbartop">
<div>
<a class="link" href="appendixa.html">Chapter Contents</a> | <a class="link" href="systemtables.html" title="Virtuoso System Tables">Prev</a> | <a class="link" href="apndxclientcompilance.html" title="Server & client versions compatibility">Next</a>
</div>
</div>
<div id="currenttoc">
<form method="post" action="/doc/adv_search.vspx">
<div class="search">Keyword Search: <br />
<input type="text" name="q" /> <input type="submit" name="go" value="Go" />
</div>
</form>
<div>
<a href="http://www.openlinksw.com/">www.openlinksw.com</a>
</div>
<div>
<a href="http://docs.openlinksw.com/">docs.openlinksw.com</a>
</div>
<br />
<div>
<a href="index.html">Book Home</a>
</div>
<br />
<div>
<a href="contents.html">Contents</a>
</div>
<div>
<a href="preface.html">Preface</a>
</div>
<br />
<div class="selected">
<a href="appendixa.html">Appendix</a>
</div>
<br />
<div>
<a href="yacc.html">YACC SQL Grammar Reference</a>
</div>
<div>
<a href="errors.html">Error Codes Reference</a>
</div>
<div>
<a href="signalsandexitcodes.html">Signals and Exit codes</a>
</div>
<div>
<a href="apparelnotes.html">Release Notes</a>
</div>
<div>
<a href="support.html">Product Support</a>
</div>
<div>
<a href="systemtables.html">Virtuoso System Tables</a>
</div>
<div class="selected">
<a href="apndxregexp.html">Basic Syntax of Regular Expressions</a>
</div>
<div>
<a href="apndxclientcompilance.html">Server & client versions compatibility</a>
</div>
<br />
</div>
<div id="text">
<a name="apndxregexp" />
<h2>21.7. Basic Syntax of Regular Expressions</h2>
<p>The two special symbols: <span class="computeroutput">'^'</span> and
<span class="computeroutput">'$'</span> indicate the <strong>start</strong>
and the <strong>end</strong> of a string respectively, like so:</p>
<ul>
<li>
<span class="computeroutput">^The</span>: matches any string
that starts with The;</li>
<li>
<span class="computeroutput">of despair$</span>: matches a
string that ends in the substring of despair;</li>
<li>
<span class="computeroutput">^abc$</span>: a string that
starts and ends with abc -- that could only be abc itself!</li>
<li>
<span class="computeroutput">notice</span>: a string that
has the text notice in it.</li>
</ul>
<p>Without either of the above special character you are allowing the pattern
to occur anywhere inside the string.</p>
<p>The symbols <span class="computeroutput">'*'</span>, <span class="computeroutput">'+'</span>,
and <span class="computeroutput">'?'</span> denote the number of times a character
or a sequence of characters may occur. What they mean is: zero or more, one or
more, and zero or one. Here are some examples:</p>
<ul>
<li>
<span class="computeroutput">ab*</span>: matches a string
that has an <strong>a</strong> followed by zero or more
<strong>b</strong>'s (a, ab, abbb, etc.);</li>
<li>
<span class="computeroutput">ab+</span>: same, but there is
at least one <strong>b</strong> (ab, abbb, etc.);</li>
<li>
<span class="computeroutput">ab?</span>: there might be a
<strong>b</strong> or not;</li>
<li>
<span class="computeroutput">a?b+$</span>: a possible <strong>a</strong>
followed by one or more <strong>b</strong>'s ending a string.</li>
</ul>
<p>You can also use <strong>bounds</strong>, which come inside braces
and indicate ranges in the number of occurrences: </p>
<ul>
<li>
<span class="computeroutput">ab{2}</span>: matches a string that has an
<strong>a</strong> followed by exactly two <strong>b</strong>'s
(abb);</li>
<li>
<span class="computeroutput">ab{2,}</span>: there are at least two
<strong>b</strong>'s (abb, abbbb, etc.);</li>
<li>
<span class="computeroutput">ab{3,5}</span>: from three to five
<strong>b</strong>'s (abbb, abbbb, or abbbbb).</li>
</ul>
<p>Note, that you must always specify the first number of a range
(i.e, <span class="computeroutput">{0,2}</span>, not <span class="computeroutput">{,2}</span>).
Also, as you may have noticed, the symbols '*', '+', and '?' have the same effect
as using the bounds <span class="computeroutput">{0,}</span>,
<span class="computeroutput">{1,}</span>, and <span class="computeroutput">{0,1}</span>,
respectively.</p>
<p>Now, to quantify a sequence of characters, put them inside parentheses:</p>
<ul>
<li>
<span class="computeroutput">a(bc)*</span>: matches a string that has
an <strong>a</strong> followed by zero or more copies of the sequence bc;</li>
<li>
<span class="computeroutput">a(bc){1,5}</span>: one through five copies of bc.</li>
</ul>
<p>There's also the '|' symbol, which works as an OR operator:</p>
<ul>
<li>
<span class="computeroutput">hi|hello</span>: matches a string that has
either hi or hello in it;</li>
<li>
<span class="computeroutput">(b|cd)ef</span>: a string that has either
bef or cdef;</li>
<li>
<span class="computeroutput">(a|b)*c</span>: a string that has a
sequence of alternating <strong>a</strong>'s and <strong>b</strong>'s
ending in a <strong>c</strong>;</li>
</ul>
<p>A period ('.') stands for any single character:</p>
<ul>
<li>
<span class="computeroutput">a.[0-9]</span>: matches a string that has
an <strong>a</strong> followed by one character and a digit;</li>
<li>
<span class="computeroutput">^.{3}$</span>: a string with exactly 3 characters.</li>
</ul>
<p>
<strong>Bracket expressions</strong> specify which characters are
allowed in a single position of a string: </p>
<ul>
<li>
<span class="computeroutput">[ab]</span>: matches a string that has
either an <strong>a</strong> or a <strong>b</strong>
(that's the same as <span class="computeroutput">a|b</span>);</li>
<li>
<span class="computeroutput">[a-d]</span>: a string that has lowercase
letters 'a' through 'd' (that's equal to <span class="computeroutput">a|b|c|d</span>
and even <span class="computeroutput">[abcd]</span>);</li>
<li>
<span class="computeroutput">^[a-zA-Z]</span>: a string that starts with a letter;</li>
<li>
<span class="computeroutput">[0-9]%</span>: a string that has a single
digit before a percent sign;</li>
<li>
<span class="computeroutput">,[a-zA-Z0-9]$</span>: a string that ends in
a comma followed by an alphanumeric character.</li>
</ul>
<p>You can also list the characters that do NOT want -- just use a '^' as
the first symbol in a bracketed expression (i.e.,
<span class="computeroutput">%[^a-zA-Z]%</span> matches a string with a character
that is not a letter between two percent signs).</p>
<p>Do not forget that bracket expressions are an exception to that
rule--inside them, all special characters, including the backslash ('\'),
lose their special powers (i.e., <span class="computeroutput">[*\+?{}.]</span>
matches exactly any of the characters inside the brackets).
To include a literal ']' in the list, make it the first character
(following a possible '^'). To include a literal '-', make it the first or last
character, or the second endpoint of a range.</p>
<table border="0" width="90%" id="navbarbottom">
<tr>
<td align="left" width="33%">
<a href="systemtables.html" title="Virtuoso System Tables">Previous</a>
<br />Virtuoso System Tables</td>
<td align="center" width="34%">
<a href="appendixa.html">Chapter Contents</a>
</td>
<td align="right" width="33%">
<a href="apndxclientcompilance.html" title="Server & client versions compatibility">Next</a>
<br />Server & client versions compatibility</td>
</tr>
</table>
</div>
<div id="footer">
<div>Copyright© 1999 - 2009 OpenLink Software All rights reserved.</div>
<div id="validation">
<a href="http://validator.w3.org/check/referer">
<img src="http://www.w3.org/Icons/valid-xhtml10" alt="Valid XHTML 1.0!" height="31" width="88" />
</a>
<a href="http://jigsaw.w3.org/css-validator/">
<img src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!" height="31" width="88" />
</a>
</div>
</div>
</body>
</html>
distrib
>
Fedora
>
14
>
x86_64
>
media
>
updates
>
by-pkgid
>
71d40963b505df4524269198e237b3e3
>
files
>
57
