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[`DataAdapter`](DataAdapter) › [`process`](DataAdapter/process)
## DataAdapter.process() method
Atomically read, modify, and save the contents of a plaintext file.
**Signature:**
```typescript
process(normalizedPath: string, fn: (data: string) => string, options?: DataWriteOptions): Promise<string>;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| <code>normalizedPath</code> | <code>string</code> | path to file/folder, use [normalizePath()](normalizePath) to normalize beforehand. |
| <code>fn</code> | <code>(data: string) => string</code> | a callback function which returns the new content of the file synchronously. |
| <code>options</code> | [`DataWriteOptions`](DataWriteOptions) | _(Optional)_ write options. |
**Returns:**
`Promise<string>`
string - the text value of the file that was written.