Jinja2 Template Parser for applying environment variables to a template.

j2env.py

#!/bin/env python
#Date: 24 August 2018
#Bugs by: Jonathan Thorpe

import os
import re
import argparse
from jinja2 import Environment, FileSystemLoader

CWD = os.path.dirname(os.path.abspath(__file__))

def transformTemplate(srcFileName, dstFileName, envPrefix):

  packer_vars = { item: os.environ[item] for item in os.environ.keys() if re.search("^%s" % (envPrefix), item) }

  j2_env = Environment(loader=FileSystemLoader(CWD))
  template = j2_env.get_template(srcFileName)
  renderedTemplate = template.render(packer_vars)
  
  with open(dstFileName, "w") as f:
    f.write(renderedTemplate)

if __name__ == '__main__':
  parser = argparse.ArgumentParser(description='Renders a specified Jinja2 template against environment variables prefixed by the specified prefix.')
  parser.add_argument('--src-file', action='store', dest='srcFileName', help='Source Template Filename', required=True)
  parser.add_argument('--dst-file', action='store', dest='dstFileName', help='Destination Filename', required=True)
  parser.add_argument('--env-prefix', action='store', dest='envPrefix', help='Environment variable prefix (defaults to PACKER_)', default='PACKER_')

  args = parser.parse_args()
  transformTemplate(args.srcFileName, args.dstFileName, args.envPrefix)