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<link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
<title>Regexp Type</title>
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<body>

<h2 id="regexp">Regexp</h2>
<p>
Regexp represents a regular expression.
<h3>Parameters</h3>
<table class="attr">
  <tr>
    <th scope="col">Attribute</th>
    <th scope="col">Description</th>
    <th scope="col">Required</th>
  </tr>
  <tr>
    <td>pattern</td>
    <td>regular expression pattern</td>
    <td>Yes</td>
  </tr>
  <tr>
    <td>refid</td>
    <td>Makes this <code>regexp</code>
      a <a href="../using.html#references">reference</a> to
      a <code>regexp</code> defined elsewhere. If specified no other
      attributes or nested elements are allowed.</td>
    <td>No</td>
  </tr>
</table>

<h3>Examples</h3>
<pre>&lt;regexp id="myregexp" pattern="alpha(.+)beta"/&gt;</pre>
<p>Defines a regular expression for later use with <var>id</var> <q>myregexp</q>.</p>
<pre>&lt;regexp refid="myregexp"/&gt;</pre>
<p>Use the regular expression with <var>id</var> <q>myregexp</q>.</p>
<h3 id="implementation">Choice of regular expression implementation</h3>
<p>Apache Ant comes with wrappers for
the <a href="https://docs.oracle.com/javase/8/docs/api/java/util/regex/package-summary.html"
target="_top"><code>java.util.regex</code>
package</a>, <a href="https://attic.apache.org/projects/jakarta-regexp.html"
target="_top">jakarta-regexp</a> and <a href="https://attic.apache.org/projects/jakarta-oro.html"
target="_top">jakarta-ORO</a>, see <a href="../install.html#librarydependencies">installation
dependencies</a> concerning the supporting libraries.</p>
<p>The property <code>ant.regexp.regexpimpl</code> governs which regular expression implementation
will be chosen.  Possible values for this property are:</p>
<ul>
<li><code class="code">org.apache.tools.ant.util.regexp.Jdk14RegexpRegexp</code></li>
<li><code class="code">org.apache.tools.ant.util.regexp.JakartaOroRegexp</code></li>
<li><code class="code">org.apache.tools.ant.util.regexp.JakartaRegexpRegexp</code></li>
</ul>
<p>It can also be another implementation of the
interface <code class="code">org.apache.tools.ant.util.regexp.Regexp</code>.
If <code>ant.regexp.regexpimpl</code> is not defined, Ant uses Jdk14Regexp as this is always
available.</p>
<p>
There are cross-platform issues for matches related to line terminator.  For example if you
use <q>$</q> to anchor your regular expression on the end of a line the results might be very
different depending on both your platform and the regular expression library you use. It
is <em>highly recommended</em> that you test your pattern on both Unix and Windows platforms before
you rely on it.</p>
<ul>
  <li>Jakarta Oro defines a line terminator as <q>\n</q> and is consistent with Perl.</li>
  <li>Jakarta RegExp uses a system-dependent line terminator.</li>
  <li><code>java.util.regex</code> uses <q>\n</q>, <q>\r\n</q>, <q>\u0085</q>, <q>\u2028</q>, <q>\u2029</q> as a
    default but is configured in the wrapper to use only <q>\n</q> (UNIX_LINE)</li>
</ul>
<p><em>We used to recommend that you use Jakarta ORO but since its development has been retired
Java's built-in regex package is likely the best choice going forward.</em></p>
<h3>Usage</h3> The following tasks and types use the Regexp type:
<ul>
<li><a href="../Tasks/replaceregexp.html">ReplaceRegExp task</a></li>
<li><a href="filterchain.html#linecontainsregexp">LineContainsRegexp filter</a></li>
</ul>
<p>These string filters also use the mechanism of regexp to choose a regular expression
implementation:</p>
<ul>
<li><a href="filterchain.html#containsregex">ContainsRegex string filter</a></li>
<li><a href="filterchain.html#replaceregex">ReplaceRegex string filter</a></li>
<li><a href="selectors.html#filenameselect">filename selector</a></li>
<li><a href="resources.html#rsel.name">name resource selector</a></li>
<li><a href="selectors.html#regexpselect">containsregexp selector</a></li>
</ul>

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