Pass environment variable from command line to yarn - windows

Question

I have a code that reads port number from environment variable or from config. Code looks like this
const port = process.env.PORT || serverConfig.port;
await app.listen(port);
To run app without defining environment variable, I run following yarn command.
yarn start:dev
This command works successfully in Linux shell and Windows command line.
Now, I want to pass environment variable. I tried following,
PORT=2344 yarn start:dev
This commands works successfully in Linux shell but failing in Windows command line. I tried following ways but couldn't get it to work.
Tried: PORT=2344 yarn start:dev
I got error: 'PORT' is not recognized as an internal or external command,
operable program or batch file.
Tried: yarn PORT=2344 start:dev
I got error: yarn run v1.17.3
error Command "PORT=2344" not found.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
Any idea please? I know, I can define environment variables from System Properties in Windows. But any way if I can do it from command line?

Answer 1

i'd suggest you use the NPM module called cross-env. it allows adding particular env variables on the command line regardless of platform. with that said, you may try:
$ cross-env PORT=2344 yarn start:dev

Answer 2

You can chain commands on the Windows command prompt with &(or &&). To set an environment variable you need to use the set command.
The result should look like this: set PORT=1234 && yarn start:dev.

Answer 3

Found a solution for this problem in Windows command prompt.
Create a .env file in project root folder (outside src folder).
Define PORT in it. In my case, contents of .env file will be,
PORT=2344
Run yarn start:dev
Application will use port number that you have specified in .env file.

Answer 4

Put .env file at root. Then following command will expose content of .env file and then run yarn start command
$ source .env && yarn start
or this command
$ export $(cat .env) && yarn start
If update any variable in .env then close the terminal and open new terminal window and can again run above command. Or else can also run unset command to remove existing var.
unset VAR_NAME

Answer 5

You can use popular package dotenv:
create a file .env in root directory
put all your env vars
e.g.:
ENV=DEVELOPMENT
run your code like this
$ node -r dotenv/config your_script.js
here the explanation:
[https://github.com/motdotla/dotenv#preload]

Answer 6

To define environment variables in the Windows command prompt we can use the set command, you can then split your call into two lines.
set PORT=2344
yarn start:dev
The set command persists within the current command prompt, so you only need to run it once.
The equivalent command in bash is 'export'.

Answer 7

FYI (not a direct answer). I was attempting this in VS Code - passing .env variables through yarn to a JavaScript app. Google had very few examples so I'm sharing this for posterity as it's somewhat related.
The following simply substitutes text normally placed directly into the package.json or script file. Use this to quickly obfuscate or externalize your delivery configurations.
In Environment Variable File (.env)
PORT=2344
In Yarn File (package.json)
source .env; yarn ./start.sh --port $PORT
In Yarn Script (start.sh)
#!/bin/bash
while [ $? != 0 ]; do
node dist/src/index.js $1; #replace with your app call#
done
The app then accepts port as a variable. Great for multi-tenant deployments.