:sig
bool file_append_contents(String file_name, String content)

:params
file_name : path to open or create
content : bytes to append
return value : `true` when the append succeeds

:see
>sys
file_append
file_put_contents
file_get_contents

:content
Appends one string to a file.

`file_append()` is the variadic convenience wrapper for ordinary page code. Use `file_append_contents()` when you already have one string buffer.

Example:

```uce
bool ok = file_append_contents("/tmp/uce-log.txt", "line\n");
```

The file is created if it does not exist.