Using .env Variables in package.json Scripts

Ever run into a CLI that requires you to pass values that you already have stored in your .env file?

I'm embarrassed to say I've written a script in the past that just was a wrapper around a CLI command just so I could call require('dotenv').config() before it. 😶

There's a better way though. Let's look at this Supabase command for generating TypeScript types from your database schema:

supabase gen types typescript --project-id PROJECT_ID_HERE > database.types.ts

I have the value for PROJECT_ID_HERE in my .env set as SUPABASE_REFERENCE_ID.

Fortunately, there is a package that can help us apply our .env and execute commands after the environment variables have been applied: env-cmd.

The important flag that we need to use is -x here, as this does the following:

Replace $var in args and command with environment variables

So our command, rewritten to use env-cmd would look like this in our package.json script:

"generate:db:types": "env-cmd -x supabase gen types typescript --project-id $SUPABASE_REFERENCE_ID > database.types.ts"