This note applies to ant version 1.7.1.

From Ant script environment variables can be used, for example ${env.JAVA_HOME} evaluates to environment variable JAVA_HOME. Do not forget to define the prefix "env" in your ant script. This can be done by adding the following line to the beginning of your ant build script:

<property environment="env"/>

If you forget this line then environment variables (e.g. ${env.JAVA_HOME} will not be defined inside your build script.

The reason for setting the prefix is to prevent name clashes: properties read from property files can be prefixed as well. Prefixing all properties from a property file can be done using the prefix attribute of the ant property task.