How does nodejs read environment variables set in command line?

Question

I feel like asking a silly question but I have googled it for a while and can't find a satisfying answer. SO doesn't such discussion either, only How to set NODE_ENV to production/development in OS X and How can I set NODE_ENV=production on Windows?

To run a command after another in one line we normally join them by ; ( or && )

So I had assumed I should run command like this PORT=3000 ; node server.js PORT=3000 ; node server.js or export PORT=3000; node server.js export PORT=3000; node server.js , just like PORT=3000 ; echo $PORT PORT=3000 ; echo $PORT

But we just put a space between PORT=3000 node server.js (without ; or && ) and PORT is read into process.env.PORT. How does shell make nodejs get environment variables? It will be better if someone can show nodejs codes.

----- update ------

The reason I was puzzled with this shell syntax (according to my limited knowledge) is that I think the general format for a Unix command line is

command options(s) filename(s)

The space in between is used to separate command from option and filename. So how can it be used to separate 2 commands as well?

Answer 1

I checked nodejs document and found the answer https://nodejs.org/api/process.html#process_process_env

So it is environ , not 2 separated commands,

Bourne-style shells support the syntax

 NAME=value command

to create an environment variable definition only in the scope of the process that executes command.

Or as bash manual 3.7.4 explained.

For python , it is os.environ['NAME']

This is also the reason why it won't work on windows: How can I set NODE_ENV=production on Windows?

Notes for Windows users, as a comment there by daw "set NODE_ENV=production && " adds a trailing space to the variable and don't use single/double quote.

I feel quite embarrassed that I almost wanted to delete my question. I keep it here in case someone else may also have this doubt. Or someone else can further explain environ or how node read it into process.env object.