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  <title>If and Unless on all tasks/nested elements</title>
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  <h1 id="if_and_unless">If And Unless</h1>

  <p><em>Since Ant 1.9.1</em>, it is possible to add <var>if</var> and <var>unless</var> attributes on all tasks and nested elements using special namespaces.</p>

  <p>In order to use this feature you need to add the following namespace declarations</p>
  <pre>
xmlns:if=&quot;ant:if&quot;
xmlns:unless=&quot;ant:unless&quot;</pre>

  <p>The <code>if</code> and <code>unless</code> namespaces support the following 3 conditions:</p>
  <dl>
      <dt><q>true</q></dt><dd>true if the value of the attribute evaluates to true</dd>
      <dt><q>blank</q></dt><dd>true if the value of the attribute is null or empty</dd>
      <dt><q>set</q></dt><dd>true if the specified property is set</dd>
  </dl>
  <pre>
&lt;project name=&quot;tryit&quot;
 xmlns:if=&quot;ant:if&quot;
 xmlns:unless=&quot;ant:unless&quot;&gt;
 &lt;exec executable=&quot;java&quot;&gt;
   &lt;arg line=&quot;-X&quot; if:true=&quot;${showextendedparams}&quot;/&gt;
   &lt;arg line=&quot;-version&quot; unless:true=&quot;${showextendedparams}&quot;/&gt;
 &lt;/exec&gt;
 &lt;condition property=&quot;onmac&quot;&gt;
   &lt;os family=&quot;mac&quot;/&gt;
 &lt;/condition&gt;
 &lt;echo if:set=&quot;onmac&quot;&gt;running on MacOS&lt;/echo&gt;
 &lt;echo unless:set=&quot;onmac&quot;&gt;not running on MacOS&lt;/echo&gt;
&lt;/project&gt;</pre>

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