In Next.js, .env is hardcoded during the build process.

However, there are many needs to set the env when running the built image, not during the build process.

This is usually because we handle local, dev, qa, and prod.

So how can we do that?

Most of the context is similar to the article below.

However, the above article excludes Windows.

You can see that Unix syntax is used in the package.json script.

This means that clean, caring Windows users who don't use dirty Unix can't use this script.

Therefore, clean and caring Windows users should put a script that runs properly on both operating systems in consideration of Unix users.

The solution is simple.

Just put a script that does the same thing as this syntax.

Install cross-env with the command above.

And the start command mentioned above is solved by modifying it as follows.

But the script is too long to read and needs to be added to the dev command as well.

{
    "dev": "npm run _env:-local && next dev",
    "dev:dev": "npm run _env:dev && next dev",
    "start": "npm run _env:-local && next start",
    "_env:-local": "cross-env-shell node ./utils/cli.js next-env -e $APP_ENV",
    "_env:dev": "node ./utils/cli.js next-env -e dev"

Therefore, I organized it as above.