ETL provides a command line utility, etl, for evaluating
templates and DDL files.
The etl command takes two flags, -I, which
allows you to specify include paths and -D which allows
you to specify String variables on the command line. For example,
etl -I templates -D foo=bar file.etl would search for
included files in the templates directory and set the variable "foo"
to the value "bar".
In addition to the template file you are evaluating, you can pass an optional DDL file. The variables within the DDL file will be passed to the ETL file when it's evaluated.