Question

Ant script

    <property environment="env">
    <if> <equals arg1="${env.PARA} arg2=""/>
    <then>
        <property name="${env.PARA}" value="abc"/>
    <then>
    <if>

    <echo message="${env.PARA}">

Output is

${env.PARA}

Expected output is

abc

I have not defined the environment variable PARA in dos. How to get the expected output.

Note : I am using ant 1.8.2 and antcontrib in windows 7

Answer 1

The following is the “ANT way” to conditionally set properties.

<project name="test" default="run">

    <property environment="env"/>

    <target name="check-prop" unless="${env.PARA}">
        <property name="env.PARA" value="abc"/>
    </target>

    <target name="run" depends="check-prop">
        <echo message="${env.PARA}"/>
    </target>

</project>

Testing

I’m a linux user, however, it should work the same on windows.

No environment variable

$ ant
Buildfile: /home/mark/tmp/build.xml

check-prop:

run:
     [echo] abc

BUILD SUCCESSFUL

environment variable

$ (export PARA="hello world"; ant)
Buildfile: /home/mark/tmp/build.xml

check-prop:

run:
     [echo] hello world

BUILD SUCCESSFUL