Can Ant expand environment variables from a properties file?

Question

I have a question regarding Ant and its treatment of environment variables. To illustrate I have a small sample.

Given the Ant build file test.xml:

Answer 1

You need to read the test.props property file after the environment - you could do so using another property task, i.e. add

<property file="test.props" />

after your existing property environment task.

In full:

<property environment="env" />
<property file="test.props" />

<target name="testProps">
    <echo message="${env.MyEnvVar}"/>
    <echo message="${MY_PROPERTY}"/>
</target>

When you supply the properties file on the command line this gets processed before the content of the build, but at that time ${env.MyEnvVar} is not yet set.