I have used the sample logback.groovy from the documentation for using a variable. Defining it within the log config file works fine but if I try to set it as a system property it does not find it. I have attached three files: build.sbt, logback.groovy, Test.scala. My test program confirms that the system property has been set correctly. When I run the command:

sbt -DUSER_HOME="/tmp"

I get the following output:

22:03:30,768 |-INFO in ch.qos.logback.classic.LoggerContext[default] - Found resource [logback.groovy] at file:/home/des/workspace/play/target/scala-2.10/classes/logback.groovy
22:03:31,449 |-INFO in ch.qos.logback.classic.gaffer.ConfigurationDelegate@5c3286d0 - About to instantiate appender of type [ch.qos.logback.core.FileAppender]
22:03:31,450 |-INFO in ch.qos.logback.classic.gaffer.ConfigurationDelegate@5c3286d0 - Naming appender as [FILE] 22:03:31,515 |-ERROR in ch.qos.logback.classic.gaffer.AppenderDelegate@7930f0f9 - Appender [FILE] of type [ch.qos.logback.core.FileAppender] has no appplicable [USER_HOME] property
22:03:31,556 |-INFO in ch.qos.logback.core.FileAppender[FILE] - File property is set to [null/myApp.log] 22:03:31,562 |-INFO in ch.qos.logback.classic.gaffer.ConfigurationDelegate@5c3286d0 - Setting level of logger [ROOT] to DEBUG
22:03:31,569 |-INFO in ch.qos.logback.classic.gaffer.ConfigurationDelegate@5c3286d0 - Attaching appender named [FILE] to Logger[ROOT]

Ubuntu Desktop 14.04, Scala 2.10, sl4j 1.7.6, groovy 2.2.1, sbt 0.13