Ant: The Definitive Guide

Usage Statements

Q: In the example from Chapter 3, you have an all target that builds everything. I don’t want the build to do anything by default. Is there a good way to pull this off?

It’s not the way, but a good way to do this is to make a “usage statement” target. Typically this target is called help and it simply echoes messages about the common targets in the build. This behavior is similar to some Unix (and some Windows) console programs. If you’re not familiar with these console programs, they normally do nothing if called from the command line with no arguments. Instead, they display a message, starting with the text “Usage” that shows the various command-line arguments you can use with the program. Our help target does the same thing, as the following example shows:

<project name="usage_example" default="help" basedir="."> <!-- some properties --> <!-- some paths --> <target name="build-lib"/> <target name="build-app"/> <target name="deploy-app"/> <target name="makedoc"/> <target name="help"> <echo message="Build the usage_example project"/> <echo message="Usage: ant [ant options] <target1> \ [target2 | target3 | ... ]"/> <echo message=""/> <echo message=" build-lib - build just the project's library"/> <echo message=" build-app - build the library and \ the application"/> <echo message=" deploy-app - ready the \ application for deployment"/> <echo message=" makedoc - generate all the \ documentation for the project"/> <echo message=" -projecthelp - (An Ant option) Display ...