How to pass paramters by refrence in ant - ant

Question

Hi all this is my code for target calling.
<target name="abc">
<var name="x" value="10"/>
<antcall target="def"/>
<!--Again Access The value of x here and also change it here-->
</target>
<target name="def">
<!--Access The value of x here and also change it here-->
</target>
and also i want to access this X in other build file,is there any way

Answer 1

This is not possible with ant. In an properties are immutable and cannot be reset. The var task from ant contrib can be used to override values, but should be used sparingly.
You could use a temporary file to achieve what you want. But probably you are trying something weird, which can be solved in a different way.
This would also work across buildfiles if they have access to the property file.
<target name="abc">
<var name="x" value="10"/>
<antcall target="def"/>
<!--Again Access The value of x here and also change it here-->
<var unset="true" file="myproperty.properties" /> <!-- read variable from property file-->
</target>
<target name="def">
<echo file="myproperty.properties" append="false">x=12</echo> <!-- create a new propertyfile-->
</target>

Answer 2

For the sake of justice, there is a hack that allows to alter ant's immutable properties without any additional libs (since java 6):
<scriptdef name="propertyreset" language="javascript"
description="Allows to assing #{property} new value">
<attribute name="name"/>
<attribute name="value"/>
project.setProperty(attributes.get("name"), attributes.get("value"));
</scriptdef>
Usage:
<target name="abc">
<property name="x" value="10"/>
<antcall target="def"/>
</target>
<target name="def">
<propertyreset name="x" value="11"/>
</target>
As #oers mentioned, this should be used with care after all canonical approaches proved not to fit.
It is difficult to suggest further without knowing the goal behind the question.