Simple search/replace config file script in Bash

configparse.sh

#!/bin/bash
# Replaces params with values and outputs
# Note: Not really designed for complex variables. So beware of sed
USAGE="configparse <infile> [param1=value1 param2=value2 .. paramn=valuen]"
# - .e.g. configparse sitebleh.tmpl DOCROOT=/data/moo USER=ano HOSTNAME=scrolls.org

if [ ! "$1" ]; then
        echo $USAGE
        exit 1
fi

if [ ! -f $1 ]; then
        echo "No template file found"
        exit 1
fi

TEMPLATE_DATA=$(cat $1)
SITENAME=$2

VARS=(${@:(2)})

for var in ${VARS[@]}
do
        key=$(echo $var | awk -F = '{ print $1}')
        value=$(echo $var | awk -F = '{ print $2}')
        TEMPLATE_DATA=$(echo "$TEMPLATE_DATA" | sed -r 's/'$key'/'$value'/g')
done

echo "$TEMPLATE_DATA"