# @ohos.app.ability.ChildProcess

**ChildProcess** is the base class for you to customize child processes. When starting a child process through [childProcessManager](js-apis-app-ability-childProcessManager.md), you must inherit this class and override the entrypoint method.

> **NOTE**
> 
> The initial APIs of this module are supported since API version 11. Newly added APIs will be marked with a superscript to indicate their earliest API version. 
> 
> The APIs of this module can be used only in the stage model.

## Modules to Import

```ts
import { ChildProcess } from '@kit.AbilityKit';
```

## ChildProcess.onStart

onStart(args?: ChildProcessArgs): void

Entrypoint method of the child process. This callback is triggered when the child process is started through [childProcessManager](js-apis-app-ability-childProcessManager.md).

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**

  | Name | Type | Mandatory | Description |
  | -------- | -------- | -------- | -------- |
  | args<sup>12+</sup> | [ChildProcessArgs](js-apis-app-ability-childProcessArgs.md) | No | Parameters transferred to the child process. |

**Example**
```ts
import { ChildProcess, ChildProcessArgs } from '@kit.AbilityKit';

export default class DemoProcess extends ChildProcess {

  onStart(args?: ChildProcessArgs) {
    let entryParams = args?.entryParams;
    let fd = args?.fds?.key1;
    // ..
  }
}
```