:sig
void file_append(String file_name, ...val)

:params
file_name : file name of file that should be written to
...val : one or more values that should be written into the file

:see
>sys

:content
Opens or creates a file and appends data to it.

## Related Concepts

- PHP: `file_put_contents($file, $data, FILE_APPEND)`
- JavaScript / Node.js: Node `fs.appendFileSync()` or `fs.promises.appendFile()`