How to get the current cursor position in file?

Question

Given this code:

let any_offset: u64 = 42;
let mut file = File::open("/home/user/file").unwrap();
file.seek(SeekFrom::Start(any_offset));
// println!("{:?}", file.cursor_position()) 

How can I obtain the current cursor position?

Answer 1

You should call Seek:seek with a relative offset of 0. This has no side effect and returns the information you are looking for.

Seek is implemented for a number of types, including:

• impl Seek for File
• impl<'_> Seek for &'_ File
• impl<'_, S: Seek + ?Sized> Seek for &'_ mut S
• impl<R: Seek> Seek for BufReader<R>
• impl<S: Seek + ?Sized> Seek for Box<S>
• impl<T> Seek for Cursor<T> where
• impl<W: Write + Seek> Seek for BufWriter<W>

Using the Cursor class mentioned by Aaronepower might be more efficient though, since you could avoid having to make an extra system call.