Multi-site, multi-install shell script

I have a situation where I am running multiple, multi-site setups. I have written a shell script to ease the use of drush.php in this instance. Maybe it will be of use to others, and if so, maybe it should be included with the module.

This script uses a single configuration directory, which contains a simple configuration file for each site you wish to use. This way i can simply specify the configuration by name, rather than needing to be in the correct directory, or specify a bunch of options.

The usage of the script is like this (i've named the script simply drush):
drush <configname> [drush options] <drush commands>
For instance, if you set up a config file named mysite.conf, you could do the following.
drush mysite cron
And as long as the drush shell script is in your PATH, this could be done from any directory.

There are 2 configurable paths in the script itself. First is for the php executable, and second is the directory containing the config files.

Here is an example configuration file, and i've attached the script.

# 
# Drush example configuration file.  
#
# Each configuration file declares the configuration for a single site.
# The name of the configuration file (without the extension) will be
# used when calling the drush script. For this file (example.conf), 
# drush would be invoked like such:
#   drush example [options] <command>
#
# IMPORTANT: Make sure there are no spaces before or after the = in the following declarations!

# base url of the site; include trailing slash
HOST=http://www.example.com/

# document root
ROOT=/var/www/html

# location of drush.php, relative to $ROOT
DRUSH=sites/all/modules/contrib/drush/drush.php