envstack 0.4.2

Stacked environment variable management system.

envstack

Stacked environment variable management system. The lightweight, easy to use "rez" alternative for production pipelines.

Environment variables are declared in namespaced .env files using yaml syntax. The default stack is stack and variables are declared in stack.env files. You can create any new stack by creating new .env files, e.g. creating a new test stack just create test.env files.

Note: envstack works best combined with siteconf.

Installation

The easiest way to install:

$ pip install envstack

Quickstart

Copy the default stack file stack.env to your current working directory, the root of your project or $DEFAULT_ENV_DIR if defined (defaults: /etc/envstack on posix platforms and C:/ProgramData/envstack on Windows).

$ cp stack.env $DEFAULT_ENV_DIR

The stack namespace is the default environment stack. Running the envstack command should show you the resolved environment for your platform:

$ envstack
ENV 'prod'
HELLO 'world'
FOO 'bar'
PYVERSION 3.11
LIB 'lib/python3.11'
LOG_LEVEL 20
ROOT '/mnt/tools/lib/python3.11'

Modify the environment stack by updating stack.env or by creating new contextual stack.env files up and down the project hierarchy.

You can execute any command inside the default stacked environment like this:

$ envstack -- <command>

For example:

$ envstack -- python -c "import os; print(os.environ['HELLO'])"
world

To create a new environment stack, create a new namespaced .env file. For example thing.env (the stack namespace is "thing"):

all: &default
  FOO: bar

To see the resolved environment for the thing environment stack, run:

$ envstack thing
FOO 'bar'

Environment stacks are hierarchical, so values for $FOO defined in .env files lower in the filesystem (lower in scope) override those defined higher up (higher in scope):

/show/thing.env
/show/seq/thing.env
/show/seq/shot/thing.env
/show/seq/shot/task/thing.env

Variables can reference other variables defined elsewhere (but cannot be circular):

all: &default
  BAR: $FOO

Variables can be platform specific (and inherit the defaults):

linux:
  <<: *default
  HELLO: world

Environment files can include other namespaced environments (all stacks inherit the default stack.env automatically).

include: ['other']

Usage

To see the default resolved environment for any given scope (directory):

$ envstack

To see the resolved environment for a given namespace.

$ envstack <stack> [OPTIONS]

To resolve a $VAR declaration for a given environment stack:

$ envstack <stack> -r <VAR>

To trace where a $VAR declaration is being set:

$ envstack <stack> -t <VAR>

To see an environment stack on another platform:

$ envstack <stack> -p <platform>

Python API

By default, envstack.getenv uses the resolved default env stack stack and can be a drop-in replacement for os.getenv

>>> import envstack
>>> envstack.getenv("HELLO")
'world'

To use a different stack, use the init function:

>>> envstack.init("thing")
>>> envstack.getenv("FOO")
'bar'

The init function also updates the current environment for code that is not using envstack:

>>> os.getenv("FOO")
'bar'

Running Commands

To run any command line executable inside of an environment stack, where <command> is the command to run:

$ envstack <stack> -- <command>

For example, running python in the default stack (reading from the default stack.env file):

$ envstack -- python -c "import os; print(os.environ['HELLO'])"
world

Same command but using the "thing" stack"

$ envstack thing -- python -c "import os; print(os.environ['FOO'])"
bar

To source the environment in your current shell, source the output of --export (and create an alias for convenience):

$ source <(envstack --export)
$ alias esinit='source <(envstack $ARG --export)'

In Windows command prompt:

for /f "usebackq" %i in (`envstack --export`) do %i

Config

Default config settings are in the config.py module. The following environment variables are supported:

Variable	Description
$DEFAULT_ENV_DIR	the folder containing the default env stack files
$DEFAULT_ENV_STACK	the name of the default env stack namespace (default "stack")