source a file containing environment variables including "dash" character in bash?

Question

I'm using bash and have a file called x.config that contains the following:

MY_VAR=Something1
ANOTHER=Something2

To load these as environment variables I just use source:

$ source x.config

But this doesn't work if MY_VAR is called MY-VAR:

MY-VAR=Something1
ANOTHER=Something2

If I do the same thing I get:

x.config:1: command not found: MY-VAR=Something1

I've tried escaping - and a lot of other things but I'm stuck. Does anyone know a workaround for this?

Well I know you can escape it if you do env 'MY-VAR=..' so I suppose there must be a workaround? — Johan, Feb 02 '16 at 11:03
@123 Because I need to pass it into an application that requires "-" — Johan, Feb 02 '16 at 11:04
@Johan What? You don't/can't pass the variable name to other applications... — 123, Feb 02 '16 at 11:09
@Johan `Well I know you can escape it if you do env 'MY-VAR=..' ` No you can't — 123, Feb 02 '16 at 11:15
@123 Sorry, what I mean is that the application reads its config from the environment (i.e. the defined environment variables) and it requires hyphen in some of the configuration names. This works for example when using when I use docker or docker-compose to read a set of predefined environment variables from a file. — Johan, Feb 02 '16 at 11:16
@Johan You can't do it, change your application to use valid env variables. — 123, Feb 02 '16 at 11:18
Possible duplicate of http://stackoverflow.com/questions/2821043/allowed-characters-in-linux-environment-variable-names — tripleee, Feb 02 '16 at 11:41
@123 I take your word for it. It would be interesting to know you docker-compose manage to do this though? But that's another question I suppose. — Johan, Feb 02 '16 at 11:58
@123 `env 'MY-VAR=3' bash` will add the variable to the environment; it's just not exposed as a shell environment variable. It will be passed to any child processes which may be able to use it. — chepner, Feb 02 '16 at 15:09

score 3 · Accepted Answer · answered Feb 02 '16 at 15:09

A pure bash workaround that might work for you is to re-run the script using env to set the environment. Add this to the beginning of your script.

if [[ ! -v myscript_env_set ]]; then
    export myscript_env_set=1
    readarray -t newenv < x.config
    exec env "${newenv[@]}" "$0" "$@"
fi

# rest of the script here

This assumes that x.config doesn't contain anything except variable assignments. If myscript_env_set is not in the current environment, put it there so that the next invocation skips this block. Then read the assignments into an array to pass to env. Using exec replaces the current process with another invocation of the script, but with the desired variables in the environment.

score 1 · Answer 2 · edited May 23 '17 at 11:45

A dash (-) in an environment variable is not portable, and as you noticed, will cause a lot of problems. You can't set these from bash. Fix the application you want to invoke.

That being said, if you can't change the target app, you can do this from python:

#!/usr/bin/python

import os

with open('x.config') as f:
    for line in f:
        name, value = line.strip().split('=')
        os.environ[name] = value

os.system('/path/to/your/app')

This is a very simplistic config reader, and for a more complex syntax you might want to use ConfigParser.

source a file containing environment variables including "dash" character in bash?

2 Answers2