/ Command-line Tools

A command-line tool for loading different bash environment profiles

A command-line tool for loading different bash environment profiles

switchenv

In my analysis work, I will frequently put auth credentials into environment variables. This allows me to check my code into Github without divulging any secrets. So, for example, I might have code in a Jupyter notebook that looks something like

import os
from my_module import get_database_connection

connection = get_database_connection(
    port=os.environ('PGPORT'),
    password=os.environ('PGPASSWORD'),
    user=os.environ('PGUSER'),
    database=os.environ('PGDATABASE'),
    host=os.environ('PGHOST'),
)

The database I connect to will be completely determined by the environment
variables I have defined.

switchenv gives me a way to easily navigate between different environments so
that, for example, I can quickly switch between development and production
databases.

Install

switchenv is written in python. You can install it with

pip install switchenv

Use Case

Imagine I have the following bash files I can source in order to set up my bash
environment the way I'd like. Typically I would just run source rc_development_db.sh before running my code in order to set up my dev
environment. However, I have to be very careful about where I place my rc files
so that I don't accidentally check them into Github. Furthermore, it can be
annoying to keep track of these files when I'd like to reuse them for different
projects. This is where switchenv comes in.

rc_development_db.sh

export MY_MESSAGE="You are in dev profile"
export PGPORT=5432
export PGPASSWORD=my_dev_password
export PGUSER=my_dev_username
export PGDATABASE=my_dev_database
export PGHOST=my_dev_host

rc_production_db.sh

export MY_MESSAGE="You are in prod profile"
export PGPORT=5432
export PGPASSWORD=my_prod_password
export PGUSER=my_prod_username
export PGDATABASE=my_prod_database
export PGHOST=my_prod_host

rc_bash_functions.sh


print_message () {
   echo "Current message is ${MY_MESSAGE}"
}

Setting up switchenv

Basic Setup

Below is copy-paste from an interactive bash session showing how to set up the
switchenv workflow.

bash>
bash> # Make sure I'm in a directory with the rc files I want
bash> ls *.sh
rc_development_db.sh  rc_production_db.sh  rc_bash_functions.sh
bash>
bash> # Load my rc scripts into switchenv giving them profile names
bash> switchenv add -p dev -f ./rc_development_db.sh
bash> switchenv add -p prod -f ./rc_production_db.sh
bash>
bash> # Profiles can hold any legal bash code, including function definitions.
bash> switchenv add -p func -f ./rc_bash_functions.sh
bash>
bash> # Show list of stored profile names
bash> switchenv list
dev
prod
func
bash>
bash> # Show contents of single profile
bash> switchenv show -p prod


#========================================
# prod
#========================================
export PGPORT=5432
export PGPASSWORD=my_prod_password
export PGUSER=my_prod_username
export PGDATABASE=my_prod_database
export PGHOST=my_prod_host

Under the hood, switchenv placed a json file in a hidden directory off of my
home directory.

~/.switchenv/profiles.json

This json file serves as the centralized data-store for all of my profile
information.

Advanced Setup (Composed profiles)

I can also create composed profiles. These profiles will source other named
profiles in the order they are specified. Any changes I make to one of the
sourced profiles will automatically carry over to the composite profile.
Composed profiles can be nested. So, a composed profile can have another composed
profile as one of its sub-profiles. Here is an example of setting up a composed profile

bash>
bash> # Create a composed profile based on two other profiles
bash> switchenv compose -c prod_with_func -p prod -p func
bash>
bash> # Show all profiles including new composite profile
bash> switchenv list
dev
prod
prod_with_func -> ['prod', 'func']
func
bash>

Now when you list profiles, you can easily identify composed profiles and see
the order in which they will execute their sub-profiles.

Navigating Between Environments with switchenv

Using switchenv involves interacting with a simple console-based UI, so it is
best illustrated using a gif. Shown here is my admittedly sub-par screen
recording of how to use switchenv.

For a more thorough description use

switchenv --help

Or use the switchenv alias (because I hate typing)

bash> sw --help

Usage: sw [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  add       Create a profile from file
  compose   Compose a new profile from existing profiles
  delete    Delete a profile
  examples  Show usage examples
  list      List all profile names
  show      Show contents of a single profile
  snapshot  Snapshot current env into a profile
  source    Drop into subshell with named profile (useful in scripts)

Just for my future reference, I made this recording by using the native OSX
screen recording feature to make a .mov file. I then used
Gif Brewary 3
to convert it to a .gif file by manually setting the speed to 150% and
frames-per-sec to 6. I let the software figure it out from there.

switchenv_demo

If you feel like digging around under the hood to see what switchenv actually sourced
when activating your environment, you can look at

~/.switchenv/switchenvrc.sh

Your subshell was essentially invoked with the command

bash --init-file ~/.switchenv/switchenvrc.sh

You can manually execute this command in a new terminal window if you would like
an exact clone of your environment in a new console.

GitHub

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