How do I run a task only if an environment variable is defined?

[mark_vieira]

You can use Task.onlyIf() to accomplish this.

task deployToTomcat(type: Copy) {
    from war.archivePath
    into "$System.env.CATALINA_HOME/webapps"
    onlyIf {
        System.env['CATALINA_HOME'] != null
    }
}