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<title>ReplaceRegExp Task</title>
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<h2><a name="replaceregexp">ReplaceRegExp</a></h2>
<h3>Description</h3>
<p>ReplaceRegExp is a directory based task for replacing the
occurrence of a given regular expression with a substitution pattern
in a selected file or set of files.</p>

<p>The output file is only written if it differs from the existing
file.  This prevents spurious rebuilds based on unchanged files which
have been regenerated by this task. In order to assess whether a file
has changed, this task will create a pre-processed version of the
source file inside of the <a href="../running.html#tmpdir">temporary
directory</a>.</p>

<p>Similar to <a href="../Types/mapper.html#regexp-mapper">regexp
type mappers</a> this task needs a supporting regular expression
library and an implementation of
<code>org.apache.tools.ant.util.regexp.Regexp</code>.
See details in the documentation of the <a href="../Types/regexp.html#implementation">Regexp Type</a>. </p>

<h3>Parameters</h3>
<table border="1" cellpadding="2" cellspacing="0">
  <tr>
    <td valign="top"><b>Attribute</b></td>
    <td valign="top"><b>Description</b></td>
    <td align="center" valign="top"><b>Required</b></td>
  </tr>
  <tr>
    <td valign="top">file</td>
    <td valign="top">file for which the regular expression should be replaced.</td>
    <td align="center">Yes if no nested <code>&lt;fileset&gt;</code> is used</td>
  </tr>
  <tr>
    <td valign="top">match</td>
    <td valign="top">The regular expression pattern to match in the file(s)</td>
    <td align="center">Yes, if no nested <code>&lt;regexp&gt;</code> is used</td>
  </tr>
  <tr>
    <td valign="top">replace</td>
    <td valign="top">The substitution pattern to place in the file(s) in place
                     of the regular expression.</td>
    <td align="center">Yes, if no nested <code>&lt;substitution&gt;</code> is used</td>
  </tr>
  <tr>
    <td valign="top">flags</td>
    <td valign="top">The flags to use when matching the regular expression.  For more
                     information, consult the Perl5 syntax<br>
                     g : Global replacement.  Replace all occurrences found<br>
                     i : Case Insensitive.  Do not consider case in the match<br>
                     m : Multiline.  Treat the string as multiple lines of input, using "^" and "$" as the start or end of any line, respectively, rather than start or end of string.<br>
                     s : Singleline.  Treat the string as a single line of input, using "." to match any character, including a newline, which normally, it would not match.<br>
    </td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">byline</td>
    <td valign="top">Process the file(s) one line at a time, executing the replacement
                     on one line at a time (<i>true/false</i>).  This is useful if you
                     want to only replace the first occurrence of a regular expression on
                     each line, which is not easy to do when processing the file as a whole.
                     Defaults to <i>false</i>.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">encoding</td>
    <td valign="top">The encoding of the file. <em>since Apache Ant 1.6</em></td>
    <td align="center">No - defaults to default JVM encoding</td>
  </tr>
  <tr>
    <td valign="top">preserveLastModified</td>
    <td valign="top">Keep the file timestamp(s) even if the file(s)
      is(are) modified.  <em>since Ant 1.8.0.</em></td>
    <td valign="top" align="center">No, defaults to false</td>
  </tr>
</table>
<h3>Examples</h3>
<pre>
&lt;replaceregexp file=&quot;${src}/build.properties&quot;
               match=&quot;OldProperty=(.*)&quot;
               replace=&quot;NewProperty=\1&quot;
               byline=&quot;true&quot;
/&gt;
</pre>
<p>replaces occurrences of the property name &quot;OldProperty&quot;
 with &quot;NewProperty&quot; in a properties file, preserving the existing
value, in the file <code>${src}/build.properties</code></p>

<h3>Parameters specified as nested elements</h3>
<p>This task supports a nested <a href="../Types/fileset.html">FileSet</a>
   element.</p>
<p>Since Ant 1.8.0 this task supports any filesystem
  based <a href="../Types/resources.html#collection">resource
    collections</a> as nested elements.</p>
<p>This task supports a nested <i><a href="../Types/regexp.html">Regexp</a></i> element to specify
   the regular expression.  You can use this element to refer to a previously
   defined regular expression datatype instance.</p>
<blockquote>
     &lt;regexp id="id" pattern="alpha(.+)beta"/&gt;<br>
     &lt;regexp refid="id"/&gt;
</blockquote>
<p>This task supports a nested <i>Substitution</i> element to specify
   the substitution pattern.  You can use this element to refer to a previously
   defined substitution pattern datatype instance.</p>
<blockquote>
     &lt;substitution id="id" expression="beta\1alpha"/&gt;<br>
     &lt;substitution refid="id"/&gt;
</blockquote>


<h3>Examples</h3>

<blockquote>
  <pre>
&lt;replaceregexp byline=&quot;true&quot;&gt;
  &lt;regexp pattern=&quot;OldProperty=(.*)&quot;/&gt;
  &lt;substitution expression=&quot;NewProperty=\1&quot;/&gt;
  &lt;fileset dir=&quot;.&quot;&gt;
    &lt;include name=&quot;*.properties&quot;/&gt;
  &lt;/fileset&gt;
&lt;/replaceregexp&gt;
</pre></blockquote>
<p>replaces occurrences of the property name &quot;OldProperty&quot;
 with &quot;NewProperty&quot; in a properties file, preserving the existing
value, in all files ending in <code>.properties</code> in the current directory</p>

<br>
<blockquote>
<pre>&lt;replaceregexp match="\s+" replace=" " flags="g" byline="true"&gt;
    &lt;fileset dir="${html.dir}" includes="**/*.html"/&gt;
&lt;/replaceregexp&gt;
</pre></blockquote>
<p>replaces all whitespaces (blanks, tabs, etc) by one blank remaining the
line separator. So with input
<blockquote>
<pre>
&lt;html&gt;    &lt;body&gt;
&lt;&lt;TAB&gt;&gt;&lt;h1&gt;    T E S T   &lt;/h1&gt;  &lt;&lt;TAB&gt;&gt;    
&lt;&lt;TAB&gt;&gt; &lt;/body&gt;&lt;/html&gt;
</pre></blockquote>
would converted to
<blockquote>
<pre>
&lt;html&gt; &lt;body&gt;
 &lt;h1&gt; T E S T &lt;/h1&gt; &lt;/body&gt;&lt;/html&gt;
</pre>
</blockquote>
</p>

<br><!-- small distance from code of the previous example -->
<blockquote>
<pre>&lt;replaceregexp match="\\n" replace="${line.separator}" flags="g" byline="true"&gt;
    &lt;fileset dir="${dir}"/&gt;
&lt;/replaceregexp&gt;
</pre></blockquote>
<p>replaces all <tt>\n</tt> markers (beware the quoting of the backslash) by a line break.
So with input
<blockquote>
<pre>
one\ntwo\nthree
</pre></blockquote>
would converted to
<blockquote>
<pre>
one
two
three
</pre>
</blockquote>
Beware that inserting line breaks could break file syntax. For example in xml:
<blockquote>
<pre>
&lt;root&gt;
  &lt;text&gt;line breaks \n should work in text&lt;/text&gt;
  &lt;attribute value=&quot;but breaks \n attributes&quot; /&gt;
&lt;/root&gt;
</pre>
</blockquote>
</p>


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