Debug Guide

This section offers a quick overview of a common debugging approach in Yao. A brief look is enough, as it will be used when building a simple application later.

## Run a Process

The `yao run` command is used to execute a single process. This is useful for debugging custom processes.

You can execute a single process to display the result in the console.

**Note:**

- The process runs on the server side.
- The console output appears in the terminal, not in the browser.

```bash
yao run utils.app.Ping # Return Yao version information

yao run models.tests.pet.Find 1 '::{}' # Return a pet with id 1

yao run not.exist.Process # Return an error message
```

## Print Debug Information

For debugging processes, you can use `console.log` or the `log` object to output debug information in your scripts.

For more information, see the runtime references. 👉 **[Runtime References](../references/yao-runtime)**

```bash
yao run scripts.test.Hello 'Yao!'   # Returns 'Hello, Yao!'

yao run scripts.test.Pets cat  # Returns a list of pets in the cat category.
```

**scripts/hello.ts**

```javascript
import { Process, log } from "@yao/runtime";

/**
 * Say hello to someone
 */
function Hello(name: string): string {
  // Output debug information to console
  console.log(`Hello, ${name}!`);

  // Output debug information to log
  log.Debug(`Hello %s`, name);

  return `Hello, ${name}!`;
}

/**
 * Get pets by category
 */
function Pets(category?: string): Record {
  category = category || "dog";

  // Execute a models.* internal process, to get pets by category
  const pets = Process("models.tests.pet.Get", {
    select: ["id", "name"],
    wheres: [{ column: "category", value: category }],
  });

  // Output debug information to console
  console.Debug(`category: ${category}, pets:`, pets);

  // Output debug information to log
  log.Info(`category: %s, pets: %#v`, category, pets);

  return pets;
}
```

## Check Logs

The default application log is stored in the `logs` directory. You can check the log files for more detailed information.

You can change the log location and level in environment variables.

For more information, see the App Configuration section.

👉 **[App configuration](./app-configuration)**