#!/bin/bash
function usage() {
    echo "usage: substenv file"
    echo "substitute value of environment variables into file using this syntax: {VAR}"
    echo "quote curly braces thus: {{"
}
if [ "$1" == "-h" ]; then 
   usage
   exit 0
elif [ "$1" == "" ]; then
    usage
    exit 1
else
    contents=\"\"\"`cat $file`\"\"\"; python  -c "import os;print $contents.format(**os.environ)"
fi