Welcome to withenv’s documentation!¶

Withenv is a tool to help manage your environment variables consistently.

The idea behind withenv is to have an easy way set environment variables prior to running some program that depends on them, leaving your shell in a sane state.

Contents:

withenv¶

We use environment variables all the time, but they can be painful to maintain because a shell is sticky. It is too easy to set an environment variable in your shell, only to have that variable stick around when you change projects.

withenv aims to help this problem by providing a simple way to prefix commands targeting YAML files that will be added to the environment prior to the command running.

See the docs for more info.

Free software: BSD license
Documentation: https://withenv.readthedocs.org

Installation¶

At the command line:

$ easy_install withenv

Or, if you have virtualenvwrapper installed:

$ mkvirtualenv withenv
$ pip install withenv

This will install the we command line tool.

Usage¶

The withenv package installs the we executable. Here is the basic usage.

$ we --env foo.yml printenv

The YAML in foo.yml gets loaded and applied to the environment. If the value already exists in the environment, that value will be overwritten.

You can also use a directory of YAML files.

$ we --dir myenv printenv

The files will be applied to the environment in alphabetical order.

You can shorten the flags as well as mixing files and directories.

$ we -e foo.yml -d bar -e baz.yml printenv

Each flag will be applied in order from left to right.

YAML Format¶

You can use a hash or list of hashes in your YAML file. For example:

---
FOO: bar
BAR: hello $FOO

It is not recommended to use a hash in this format because the order cannot be gauranteed, although, it will probably work just fine. If you need explicit ordering within your file, use a list of hashes.

---
- FOO: bar
- BAR: hello $FOO

Here we see the $FOO variable is used within the value of $BAR.

Environment Files¶

Withenv also makes an effort to include environment files. Specifically, you can include a file that use the format:

export $VARNAME=$VALUE

Each line is parsed as an entry. This can be a typical shell script as lines that don’t start with export will be ignored. With that in mind, functions defined in the script will not be available.

Command Substitutions¶

Sometimes you want to replace a variable based on the result of a command. Say for example, you wanted to grab a value from a chef environment. We can use the knife and jq to grab the value and inject into our environment value.

---
- CHEF_ENV: dev
- TOKEN: "`knife environment show $CHEF_ENV -Fj | jq --raw-output .default_attributes.token`"

The knife command will go to our chef server and grab the environment’s configuration and output it as JSON. This output is piped to the jq command where we are able to use JSONPath to grab the field value we need. The –raw-output will ensure we don’t have any quotes around the value.

We could then use this in a commmand.

$ we -e token.yml curl -H 'X-Auth-Token: $TOKEN' http://example.com/api/

Currently, withenv supports this dynamic substitution when the value starts and endswith a backtick.

Creating an Alias¶

Sometimes you’ll find that your environment is composed of a suite of details. Say for example, you were deploying an application via some script that uses environment variables to choose what region, cloud account and process to run.

$ we -d envs/apps/foo \
     -e envs/acct/dev.yml \
     -e envs/regions/us-east \
     -E TAG=foo
     ./create-app-server

We can create an alias for this by creating an alias YAML file.

# myalias.yml
---
- directory: envs/apps/foo
- file: envs/acct/dev.yml
- file: envs/regions/us-east
- override: "TAG=foo"

We can then run our command with a shortened we command.

$ we -a myalias create-app-server

Loading Defaults¶

Withenv will look for a default alias file called .werc. The we command will look in the current directory and walk the filesystem until it finds a .werc file. If it finds a .werc, it will load it as an alias file prior to any command line arguments. If no .werc is found, we continues normally.

For example, lets say that you had a some projects for different clients. Each client provided credentials to a cloud account and you want to use the specific client when running commands.

The .werc might look like this:

# .werc
---
- file: client.yml
- file: ~/projects/clients/$CLIENT/creds.yml

The client.yml would add the $CLIENT env var. Now you could see what instances your client has running.

$ we ec2-describe-regions
# or for rackspace
$ we rack servers instance list

Contributing¶

Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

You can contribute in many ways:

Types of Contributions¶

Report Bugs¶

Report bugs at https://github.com/ionrock/withenv/issues.

If you are reporting a bug, please include:

Your operating system name and version.
Any details about your local setup that might be helpful in troubleshooting.
Detailed steps to reproduce the bug.

Fix Bugs¶

Look through the GitHub issues for bugs. Anything tagged with “bug” is open to whoever wants to implement it.

Implement Features¶

Look through the GitHub issues for features. Anything tagged with “feature” is open to whoever wants to implement it.

Write Documentation¶

withenv could always use more documentation, whether as part of the official withenv docs, in docstrings, or even on the web in blog posts, articles, and such.

Submit Feedback¶

The best way to send feedback is to file an issue at https://github.com/ionrock/withenv/issues.

If you are proposing a feature:

Explain in detail how it would work.
Keep the scope as narrow as possible, to make it easier to implement.
Remember that this is a volunteer-driven project, and that contributions are welcome :)

Get Started!¶

Ready to contribute? Here’s how to set up withenv for local development.

Fork the withenv repo on GitHub.

Clone your fork locally:

$ git clone git@github.com:your_name_here/withenv.git

Install your local copy into a virtualenv. This is how you set up your fork for local development:
```
$ cd withenv/
$ make bootstrap
```
Create a branch for local development:
```
$ git checkout -b name-of-your-bugfix-or-feature
```
Now you can make your changes locally.
When you’re done making changes, check that your changes pass flake8 and the tests, including testing other Python versions with tox:
```
$ make test-all
```

Commit your changes and push your branch to GitHub:

$ git add .
$ git commit -m "Your detailed description of your changes."
$ git push origin name-of-your-bugfix-or-feature

Submit a pull request through the GitHub website.

Pull Request Guidelines¶

Before you submit a pull request, check that it meets these guidelines:

The pull request should include tests.
If the pull request adds functionality, the docs should be updated. Put your new functionality into a function with a docstring, and add the feature to the list in README.rst.
The pull request should work for Python 2.6, 2.7, 3.3, and 3.4, and for PyPy. Check https://travis-ci.org/ionrock/withenv/pull_requests and make sure that the tests pass for all supported Python versions.

Tips¶

To run a subset of tests:

$ py.test tests/test_my_test.py::TestClass::test_func