Sometimes we have to execute some tasks from the command line. These tasks can serve different purposes such as populating a database (user creation, etc) for instance. They often need to access some of the app classes and functions. This is when shell scripts come into play.

Create Scripts

A shell script is just a TypeScript file located in the src/scripts. It must export a main function that is then called when running the script.

Let's create a new one with the command line: foal g script display-users. A new file with a default template should appear in you src/scripts directory.

Write Scripts

Remove the content of src/scripts/display-users.ts and replace it with the below code.

// 3p
import { createConnection } from 'typeorm';

// App
import { User } from '../app/entities';

export async function main() {
  const connection = await createConnection();
  const users = await connection.getRepository(User).find();
  console.log(users);
}

As you can see, we can easily establish a connection to the database in the script as well as import some of the app components (the User in this case).

Encapsulating your code in a main function without calling it directly in the file has several benefits:

• You can import and test your main function in a separate file.
• Using a function lets you easily use async/await keywords when dealing with asynchronous code.

Build and Run Scripts

To run a script you first need to build it.

npm run build:scripts

Then you can execute it with this command:

foal run my-script # or foal run-script my-script

You can also provide additionnal arguments to your script (for example: foal run my-script foo=1 bar='[ 3, 4 ]'). The default template in the generated scripts shows you how to handle such behavior.