Load .env files and expends (substitute) vars https://sorokin.engineer/posts/en/jenkins_load_env_vars_with_expanding.html

expand_vars.py

"""
Loads a number of files listed in args:
    python expand_vars.py file1 file2 ...
Expects line format like
    key=value
Skips comments and empty lines.
Substitute vars $var / ${var} from system environment and from previous lines / files/

Universal Python 2 / 3 module to use on any Jenkins agent.
"""
from __future__ import print_function

import os
import os.path
import sys


def expand_vars(file_name):
    for line in open(file_name, "r"):
        line = line.strip()
        if not line or line.startswith("#"):
            continue  # skip comments and empty lines
        key = line.split("=")[0]
        value = os.path.expandvars("=".join(line.split("=")[1:]))
        for quote in ['"', "'"]:
            if value.startswith(quote) and value.endswith(quote):
                value = value[1:-1]
                break  # do not remove nested quotes
        os.environ[key] = value
        print("%s=%s" % (key, value))


if __name__ == "__main__":
    for file_idx in range(1, len(sys.argv)):
        expand_vars(sys.argv[file_idx])