Print Environment

Logs all environment variables except a predefined set commonly present on Linux/Unix.

Useful for debugging only the environment variables relevant to your application.

Helpful during the start phase of your application, if you happen to configure your app through environment variables (which is common for apps deployed to The Cloud™). A typical Linux/Unix environment will have several dozen declared environment variables, of which most of the time only a fraction is interesting for your application and thus for you to see in its debug output.

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The exported function of this module takes the array that is process.env and sorts it, then puts it through a filter with an internal negative list and finally feeds it formatted as KEY = value into a logging sink. The filter will strip away most of the clutter and save you some scrolling on your dev terminal.

The function takes one parameter, which must be another function that will take one string argument. This "sink" is obviously the logger of your choice, be it good old console.log or an instance of debug or something completely different with a compatible signature.

export function printEnvironment(logger : (string) => void) : void

Usage and Examples

You would typically use it in some way like

const printEnv = require('print-env');
const log = require('debug')('app:env');

printEnv(log);

A declaration for TypeScript is included. The use then is equivalent to the ES6 import syntax:

import printEnv from 'print-env';
import createDebug from 'debug';

const debug = createDebug('app:env');
printEnv(debug);

You will receive output on your terminal (staying with the debug example) like this:

app:env DEBUG = *,-express:* +3ms
app:env DIFF = /usr/bin/meld +0ms
app:env HOME = /home/horst +0ms
app:env LANG = nb_NO.utf8 +1ms
app:env LANGUAGE = nb_NO +0ms
app:env MAIL = /var/mail/horst +0ms
app:env NODE_ENV = development +0ms
app:env PATH = /usr/local/bin:/usr/bin:/bin +0ms
app:env PWD = /home/horst/test +1ms
app:env USER = horst +0ms

The example output above is taken from a box where the environment contains nearly a hundred exported variables. Most of it is gone here, the basic stuff (like HOME or PWD) was left in.

The Negative-List

For a list of all the filtered expressions, check the main file of the repository.

• This list is almost certainly not complete but rather based on what runs on my current boxes. I will take suggestions (open a pull request).
• This list might filter out things that your project depends on (and what you therefore would like to have printed anyhow). Don't use it then, or rather fork it and modify to your requirements. I have no plans to make this configurable, but simply because of lacking a brilliant idea how to do so without breaking its simple API. Suggestions welcome.
• The filter creates one large regular expression during function execution. There are probably more performant takes on this, but this is supposed to be a one-shot during application startup and therefore really not a priority.

Have fun, be nice and make something!

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Copyright © 2017 Philipp Gröschler

The MIT License