env-ctrl - (Environment Control)

What is this?

This is a CLI tool for launching other programs in an isolated environment (as in full control over which environment variables are available to it).

By default it will launch the program with an empty environment; and you will have to define which variables to set or pass through.

But why?

Because using environment variables (alias EV) is a great way to send arguments to a program as an alternative to command line arguments (alias CLA).

But if a program supports them and is looking for e.g. a variable called X and it is already set as a global EV; then if you don't explicitly set it when launching the program it will instead use the global variable.

Hence a quick and easy way to control which global EVs are passed through is an essential tool to have when launching such programs!

Why favor EVs over CLAs?

1. They require no parsing logic; hence they're easier for a developer to implement.
2. They follow a standard format unlike CLAs (which you never know how are parsed).
3. They're often less confusing to use.

The CLAs of this software

env-ctrl [...ENV-VARIABLES] - program-to-run

E.g. env-ctrl PATH - program-to-run to only pass through the PATH environment variable.

And you can also define EVs in the CLAs, e.g. env-ctrl USER=Joakim PATH - program-to-run to define an EV named USER and also pass through the PATH (as a direct alternative to USER=Joakim env-ctrl USER PATH - program-to-run).

If you don't want to set or pass through any EVs then you can just do env-ctrl program-to-run to pass it an environment with no variables set.

--print-environment

We also support an argument called --print-environment which can be used to check which environment variables are set.

This can be used to check what is passed through to a program you want to launch. E.g. like this:

TEST='a test' env-ctrl TEST - env-ctrl --print-environment

There we set the TEST EV and pass it through, the output is then:

{ TEST: 'a test' }

How to install it?

First you need to have Node.js on your system, then you can install it like this:

npm i -g env-ctrl

The End

That's all for now.

Take care.