Default file pattern and placeholders

[DamienIrving]

It's not the most elegant solution (i.e. the placeholders in the file names are a little ugly), but it means people only have to write one wrapper for their command line functions and should never need to alter that wrapper, so I think it's worth doing. Perhaps in future we'll come up with a more elegant solution.

[captainceramic]

It is worth thinking about, but a good solution to move forward for the present. Thanks!