Is it possible to set system environment variables from a node script?

Question

I have an npm script like this that executes two node files:

package.json

{
  "scripts": {
    "my-target": "node setup.js && node run.js"
  }
}

Ideally, I can set environment variables in setup.js that can then be accessed in run.js.

setup.js

process.env.HELLO_WORLD=1

run.js

// Ideally prints `1`, instead prints undefined.
console.log(process.env.HELLO_WORLD);

Is something like this possible? Ideally the result of setting the environment variables in setup.js would be persistent, so that if I run

$ echo $HELLO_WORLD

from bash, that reference would still be there.

Why would you not just run HELLO_WORLD=1 node setup.js && node run.js? — Jared Smith
– Jared Smith, Commented Sep 23, 2021 at 1:20
because in reality the situation is more complex, I simplified it here to demonstrate what is needed. That is, I do not know what the value of the environment variable should be - it is dynamically determined by the setup script. — johncorser
– johncorser, Commented Sep 23, 2021 at 2:26
What you're attempting is impossible. Env vars are private to each process. When a process starts it inherits env vars from its parent. A process cannot modify the env of a different process. — Kurtis Rader
– Kurtis Rader, Commented Sep 23, 2021 at 16:42

Samuel Goldenbaum · Accepted Answer · 2021-09-23 01:41:12Z

1

You can set env vars when you run the main program:

HELLO_WORLD=hello npm run my-target

package.json:

  "scripts": {
    "my-target": "node setup.js && node run.js"
  },

setup.js:

console.info('setup', process.env.HELLO_WORLD);

run.js:

console.info('run', process.env.HELLO_WORLD);

Output will be

setup hello
run hello

answered Sep 23, 2021 at 1:41

Samuel Goldenbaum

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3 Comments

johncorser Over a year ago

This is not what I am looking for. I do not actually know what the value of the environment variable should be - it is dynamically determined by the setup script.

Samuel Goldenbaum Over a year ago

This is not a really standard way of doing things, is there a reason the two scripts need to be separate like this?

Samuel Goldenbaum Over a year ago

Ideally, you would run setup.js which would determine your dynamic values/set env vars and you then require/import run.js and execute its functions as needed.

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