> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/f/file-input/output.md).

# Output

```ruby
var in = %f'input.txt'.open_r;
var out = %f'output.txt'.open_w;
 
in.each { |line|
    out.print(line);
};
```