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<img alt="->" src="../images/arrow.gif" /> <trycatch></td>
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v0.92</td>
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<h1><trycatch></h1>
<p> Executes a set of tasks, and optionally catches a build exception to allow recovery or rollback steps to be taken, or to define some steps to be taken regardless if the tasks succeed or fail, or both. </p>
<p> The tasks defined in the <code><<code>try</code>></code> block will be executed in turn, as they normally would in a target. </p>
<p> If a <code><<code>catch</code>></code> block is defined, the tasks in that block will be executed in turn only if one of the tasks in the <code><<code>try</code>></code> block fails. This failure will then be suppressed by the <code><<code>catch</code>></code> block. </p>
<p> The message associated with the failure can also be caught in a property for use within the <code><<code>catch</code>></code> block. The original contents of the property will be restored upon exiting the <code><<code>catch</code>></code> block. </p>
<p> If a <code><<code>finally</code>></code> block is defined, the tasks in that block will be executed after the tasks in both the <code><<code>try</code>></code> and <code><<code>catch</code>></code> blocks have been executed, regardless of whether any task fails in either block. </p>
<h3>Parameters</h3>
<div class="table">
<table>
<tr>
<th>Attribute</th>
<th style="text-align: center;">Type</th>
<th>Description</th>
<th style="text-align: center;">Required</th>
</tr>
<tr>
<td valign="top">failonerror</td>
<td style="text-align: center;">bool</td>
<td> Determines if task failure stops the build, or is just reported. The default is <b>true</b>. </td>
<td style="text-align: center;">False</td>
</tr>
<tr>
<td valign="top">if</td>
<td style="text-align: center;">bool</td>
<td> If <b>true</b> then the task will be executed; otherwise, skipped. The default is <b>true</b>. </td>
<td style="text-align: center;">False</td>
</tr>
<tr>
<td valign="top">unless</td>
<td style="text-align: center;">bool</td>
<td> Opposite of <code>if</code>. If <b>false</b> then the task will be executed; otherwise, skipped. The default is <b>false</b>. </td>
<td style="text-align: center;">False</td>
</tr>
<tr>
<td valign="top">verbose</td>
<td style="text-align: center;">bool</td>
<td> Determines whether the task should report detailed build log messages. The default is <b>false</b>. </td>
<td style="text-align: center;">False</td>
</tr>
</table>
</div>
<h3>Nested Elements:</h3>
<!--Element-->
<h4>
<a id="try">
</a>
<try>
</h4>
<div class="nested-element"> The tasks in this block will be executed as a normal part of the build script. <p> Executes embedded tasks/elements in the order in which they are defined. </p><p /></div>
<h4>
<a id="try">
</a>
</try>
</h4>
<!--Element-->
<h4>
<a id="catch">
</a>
<catch>
</h4>
<div class="nested-element"> The tasks in this block will be executed if any task in the try block fails. <p></p><h3>Parameters</h3><div class="table"><table><tr><th>Attribute</th><th style="text-align: center;">Type</th><th>Description</th><th style="text-align: center;">Required</th></tr><tr><td valign="top">property</td><td style="text-align: center;">string</td><td> Defines the name of the property to save the message describing the failure that has been caught. </td><td style="text-align: center;">False</td></tr></table></div><p /></div>
<h4>
<a id="catch">
</a>
</catch>
</h4>
<!--Element-->
<h4>
<a id="finally">
</a>
<finally>
</h4>
<div class="nested-element"> The tasks in this block will always be executed, regardless of what happens in the try and catch blocks. <p> Executes embedded tasks/elements in the order in which they are defined. </p><p /></div>
<h4>
<a id="finally">
</a>
</finally>
</h4>
<h3>Examples</h3>
<ul class="examples">
<li>
<pre class="code">
<trycatch>
<try>
<echo message="In try" />
<fail message="Failing!" />
</try>
<catch>
<echo message="In catch" />
</catch>
<finally>
<echo message="Finally done" />
</finally>
</trycatch>
</pre>
<p> The output of this example will be: </p>
<pre class="code">In try
In catch
Finally done
</pre>
<p> The failure in the <code><<code>try</code>></code> block will not cause the build to fail. </p>
</li>
<li>
<pre class="code">
<trycatch>
<try>
<echo message="In try" />
<fail message="Just because..." />
</try>
<catch property="failure">
<echo message="Caught failure: ${failure}" />
<fail message="Bad catch" />
</catch>
<finally>
<echo message="Finally done" />
</finally>
</trycatch>
</pre>
<p> The output of this example will be: </p>
<pre class="code">In try
Caught failure: Just because...
Finally done
Build failed: Bad catch
</pre>
<p> Like the above, the failure in the <code><<code>try</code>></code> block does not cause the build to fail. The failure in the <code><<code>catch</code>></code> block does, however. Note that the <code><<code>finally</code>></code> block is executed even though the <code><<code>catch</code>></code> block failed. </p>
</li>
<li>
<pre class="code">
<trycatch>
<try>
<echo message="In try" />
<fail message="yet again" />
</try>
<catch property="failure">
<echo message="Caught failure ${failure}" />
<fail message="Bad catch" />
</catch>
<finally>
<echo message="Finally done ${failure}" />
</finally>
</trycatch>
</pre>
<p> The output of this example will be: </p>
<pre class="code">In try
Caught failure yet again
Build failed: Property 'failure' has not been set.
</pre>
<p> The <a href="../tasks/echo.html"><echo></a> task in the <code><<code>finally</code>></code> block failed because the "failure" property was not defined after exiting the <code><<code>catch</code>></code> block. Note that the failure in the <code><<code>finally</code>></code> block has eclipsed the failure in the <code><<code>catch</code>></code> block. </p>
</li>
<li>
<pre class="code">
<trycatch>
<try>
<property name="temp.file" value="${path::get-temp-file-name()}" />
<do-stuff to="${temp.file}" />
<fail message="Oops..." />
</try>
<finally>
<echo message="Cleaning up..." />
<if test="${property::exists('temp.file')}">
<delete file="${temp.file}" />
</if>
</finally>
</trycatch>
</pre>
<p> A more concrete example, that will always clean up the generated temporary file after it has been created. </p>
</li>
</ul>
<h3>Requirements</h3>
<div style="margin-left: 20px;">
<b>Assembly:</b> NAnt.Core (0.92.4543.0)
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