Chapter 8. Unset Task
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## Chapter 8. Unset Task

The Unset task provides easier access to one of the most used use cases of Variable, the ability to unset a property. By design, Ant properties are immutable, but sometimes it is handy to set a property to a new value.

To use this task in your build files, include a task definition like this:

        <taskdef name="unset" classname="ise.antelope.tasks.Unset"/>

Table 8.1. Unset Task Attributes

Attribute | Description | Default | Required
--- | --- | --- | ---
name | The name of the property to unset. | None | Yes, unless 'file' is used.
file | The name of a property file. All properties references in the file will be unset. This means you can load a bunch of properties from a file, then unset them all with a single line. | None | Yes, unless 'name' is used.

Example:

    <project name="unset_example" basedir=".">
        <taskdef resource="ise/antelope/tasks/antlib.xml"/>
        <property name="x" value="6"/>
        <echo>original value = ${x}</echo>
        <unset name="x"/>
        <echo>unset: ${x}</echo>
        <property name="x" value="hello"/>
        <echo>new value = ${x}</echo>
    </project>

    $ ant -f unset_example.xml
    Buildfile: unset_example.xml
         [echo] original value = 6
         [echo] unset: ${x}
         [echo] new value = hello

    BUILD SUCCESSFUL
    Total time: 0 seconds

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