I would like to set the log location for a file appender based on a directory variable, with a fall back to the current directory. In the appender section, I have

<file>${log.dir:-${user.dir}}/slave.log</file>

and the jvm is invoked with -Dlog.dir=/mnt/log to set the log location. If I leave out the default value and just use ${log.dir} this works fine, but with the default value the application throws errors while trying to instantiate the appender, indicating that it could not open the file "/mnt/log}/slave.log". The curly bracket should not be there; it seems that this must be due to a bug in the parsing code.