Source code for runway.cfngin.lookups.handlers.envvar

"""Environment variable lookup."""
# pylint: disable=unused-argument,arguments-differ
import os

from runway.lookups.handlers.base import LookupHandler

from ...util import read_value_from_path

TYPE_NAME = "envvar"

[docs]class EnvvarLookup(LookupHandler): """Environment variable lookup."""
[docs] @classmethod def handle(cls, value, context=None, provider=None, **kwargs): """Retrieve an environment variable. Args: value (str): Parameter(s) given to this lookup. context (:class:`runway.cfngin.context.Context`): Context instance. provider (:class:`runway.cfngin.providers.base.BaseProvider`): Provider instance. Example: :: # With CFNgin we would reference the environment variable like this: conf_key: ${envvar ENV_VAR_NAME} You can optionally store the value in a file, ie:: $ cat envvar_value.txt ENV_VAR_NAME and reference it within CFNgin (NOTE: the path should be relative to the CFNgin config file):: conf_key: ${envvar file://envvar_value.txt} # Both of the above would resolve to conf_key: ENV_VALUE """ value = read_value_from_path(value) try: return os.environ[value] except KeyError: raise ValueError('EnvVar "{}" does not exist'.format(value))