How to override env file on newman run?

How to rewrite variables in Newman? I have a file with my environment variables that are rewritten after a request is executed, everything works in Postman (RUN FOLDER), but in Newman all tests crash. Many of my variables do not have initial values, they only acquire them when a test passes. For example there is a POST request that adds a user, the body of the response will return to me:

{
    "id": null,
    "result": {
        "id": "c9497eb1-e4ea-47f0-a00e-a46cf8ef07a7"
    },
    "success": true
}

I take the value of the ID, and override the variable with the following command:

var jsonData = pm.response.json();
pm.environment.set('newUserId', jsonData.result.id);

When running Newman, everything crashes. Please help, if you would be so kind.

What key should I use when starting Newman? Or how to achieve positive results in NEWMAN to be like in Postman, is there such an option for processing variables?

Many tests drops when I use env value in URL path, like https://some-url/check/{createdUserId}.

You can export also environment variable too. The 'newman' running no problem if using exported environment variable

How to export environment variable.

Select 'environment quick look' - right/top icon in Postman

Select 'edit' menu

Select See more action (...)

Run newman with exported environment.json

newman run my.postman_collection.json  -e my.postman_environment.json

Demo

#1 running a local API server for adding user and getting user

#2 postman call

#3 running collection

#4 newman running

#1 running a local API server

Save as 'server'js'

const express = require('express');
const cors = require('cors');
const uuid = require('uuid');

const app = express();
const port = 3000;

app.use(express.json());
app.use(cors());

const users = {}; // Memory storage for user data

// API 1: Create(Add) user by POST
app.post('/createUser', (req, res) => {
  const { first_name, last_name, email } = req.body;
  const userId = uuid.v4(); // Generate a new UUID for the user

  users[userId] = { first_name, last_name, email }; // Store user data in memory

  res.status(201).json({
    id: null, // You can set this to any specific value if needed
    result: {
      id: userId,
    },
    success: true,
  });
});

// API 2: Get user by GET
app.get('/getUser/:user_id', (req, res) => {
  const userId = req.params.user_id;
  const user = users[userId];

  if (!user) {
    return res.status(404).json({ error: 'User not found' });
  }

  res.json({
    first_name: user.first_name,
    last_name: user.last_name,
    email: user.email,
  });
});

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});

Install dependencies

npm install express cors uuid

Running server

node server.js

#2 postman call

Create User 1 and get User 1, checked user information (name and email) Key is using user-id environment variable for POST (Adding)/GET(Getting) user pair.

If not matched Adding user/ Getting user, something wrong.

POST returned

{
    "id": null,
    "result": {
        "id": {"uuid"}
    },
    "success": true
}

GET user

http://localhost:3000/getUser/{{user-id : uuid}}

Response

{"first_name":"Steve","last_name":"Jobs","email":"steve_jobs@example.com"}

It can confirmed created user and get user is same or not by calling GET with uuid

This format

Create User1

Tests tab for adding user

POST call

http://localhost:3000/createUser

var jsonData = JSON.parse(responseBody);
postman.setEnvironmentVariable("user-id", jsonData.result.id);
console.log(pm.environment.get("user-id"));

Body

{
    "first_name": "Steve", 
    "last_name":"Jobs", 
    "email": "steve_jobs@example.com"
}

Get User1

Tests tab for adding user

GET call

http://localhost:3000/getUser/{{user-id}}

var jsonData = JSON.parse(responseBody);
console.log(jsonData);

pm.expect(jsonData.first_name).to.eql("Steve");
pm.expect(jsonData.last_name).to.eql("Jobs");
pm.expect(jsonData.email).to.eql("steve_jobs@example.com");

Add user 2 with different user information

#3 running collection on Postman

#4 newman running on terminal

newman run 1-1-demo.postman_collection.json  -e demo.postman_environment.json