grass on batch?

[Agustin Lobo]

I have written a script file that uses r.mapcalc and other grass4.1
commands. It
takes a long time because it is an iterative process that ends by
convergence and I would like to run it on batch, may be using nohup.
The problem is that grass has to be running in order to use grass
commands. How could I send this script to
batch, say, overnight? Is there any way to start a grass session from
the script?
Thanks