Ant provides some built-in properties

Property Name	Value
basedir	the absolute path of the project's basedir
ant.file	the absolute path of the buildfile.
ant.version	the version of Ant
ant.project.default-target	the name of the currently executing project's default target
ant.project.name	name of the project
ant.java.version	JVM version Ant detected

In this example, We will create custom ant properties and use them to create a temporary directory and copy a file in it.

1. Properties declared within same file.

<project name="Test Project for Ant" default="init">
    <property name="temp.dir" value="${basedir}/temp" />

    <target name="init" description="initialize">
        <mkdir dir="${temp.dir}" />
        <copy file="${basedir}/test.xml" todir="${temp.dir}/" />
    </target>
</project>

In Ant, ${basedir} will refer to the base location or the location where your ant file is present. Here I declared a property named as

temp.dir

which will refer to basedir/temp location.

So, we call target init it will replace the placeholder ${temp.dir} with its actual value and start executing our script. This target will create a directory named temp under base directory copy test.xml file to temp directory.

2. Properties declared in different files.

In this example, We will refer properties declared in different file. This is a sample file(app_version.xml) which contains application version.

<project name="Project Properties">
     <property name="app.version" value="1.0" />
</project>

To include this file we will add the import ant task to import this file while executing ant targets.

<import file="app_version.xml" />

Above code will look like

<project name="Test Project for Ant" default="init">
<import file="app_version.xml" />
<property name="temp.dir" value="${basedir}/temp" />

<target name="init" description="initialize">
    <mkdir dir="${temp.dir}" />
    <copy file="${basedir}/test.xml" todir="${temp.dir}/" />
    <echo message="App version is:${app.version}" />
</target>

Once the file is imported, it can be directly accessed via property name(app.version).

I used .xml file, same use case will also work for .properties files.